diff --git a/cachegrind/cg_main.c b/cachegrind/cg_main.c
index 20fafbc5f..559eea910 100644
--- a/cachegrind/cg_main.c
+++ b/cachegrind/cg_main.c
@@ -1563,7 +1563,6 @@ static UInt ULong_width(ULong n)
 
 static void cg_fini(Int exitcode)
 {
-   static HChar buf1[128], buf2[128], buf3[128], buf4[123];  // FIXME
    static HChar fmt[128];   // OK; large enough
 
    CacheCC  D_total;
@@ -1599,11 +1598,10 @@ static void cg_fini(Int exitcode)
       VG_(umsg)(fmt, "LLi misses:   ", Ir_total.mL);
 
       if (0 == Ir_total.a) Ir_total.a = 1;
-      VG_(percentify)(Ir_total.m1, Ir_total.a, 2, l1+1, buf1);
-      VG_(umsg)("I1  miss rate: %s\n", buf1);
-
-      VG_(percentify)(Ir_total.mL, Ir_total.a, 2, l1+1, buf1);
-      VG_(umsg)("LLi miss rate: %s\n", buf1);
+      VG_(umsg)("I1  miss rate: %*.2f%%\n", l1,
+                Ir_total.m1 * 100.0 / Ir_total.a);
+      VG_(umsg)("LLi miss rate: %*.2f%%\n", l1,
+                Ir_total.mL * 100.0 / Ir_total.a);
       VG_(umsg)("\n");
 
       /* D cache results.  Use the D_refs.rd and D_refs.wr values to
@@ -1626,15 +1624,14 @@ static void cg_fini(Int exitcode)
       if (0 == D_total.a)  D_total.a = 1;
       if (0 == Dr_total.a) Dr_total.a = 1;
       if (0 == Dw_total.a) Dw_total.a = 1;
-      VG_(percentify)( D_total.m1,  D_total.a, 1, l1+1, buf1);
-      VG_(percentify)(Dr_total.m1, Dr_total.a, 1, l2+1, buf2);
-      VG_(percentify)(Dw_total.m1, Dw_total.a, 1, l3+1, buf3);
-      VG_(umsg)("D1  miss rate: %s (%s     + %s  )\n", buf1, buf2,buf3);
-
-      VG_(percentify)( D_total.mL,  D_total.a, 1, l1+1, buf1);
-      VG_(percentify)(Dr_total.mL, Dr_total.a, 1, l2+1, buf2);
-      VG_(percentify)(Dw_total.mL, Dw_total.a, 1, l3+1, buf3);
-      VG_(umsg)("LLd miss rate: %s (%s     + %s  )\n", buf1, buf2,buf3);
+      VG_(umsg)("D1  miss rate: %*.1f%% (%*.1f%%     + %*.1f%%  )\n",
+                l1, D_total.m1  * 100.0 / D_total.a,
+                l2, Dr_total.m1 * 100.0 / Dr_total.a,
+                l3, Dw_total.m1 * 100.0 / Dw_total.a);
+      VG_(umsg)("LLd miss rate: %*.1f%% (%*.1f%%     + %*.1f%%  )\n",
+                l1, D_total.mL  * 100.0 / D_total.a,
+                l2, Dr_total.mL * 100.0 / Dr_total.a,
+                l3, Dw_total.mL * 100.0 / Dw_total.a);
       VG_(umsg)("\n");
 
       /* LL overall results */
@@ -1651,10 +1648,10 @@ static void cg_fini(Int exitcode)
       VG_(umsg)(fmt, "LL misses:    ",
                      LL_total_m, LL_total_mr, LL_total_mw);
 
-      VG_(percentify)(LL_total_m,  (Ir_total.a + D_total.a),  1, l1+1, buf1);
-      VG_(percentify)(LL_total_mr, (Ir_total.a + Dr_total.a), 1, l2+1, buf2);
-      VG_(percentify)(LL_total_mw, Dw_total.a,                1, l3+1, buf3);
-      VG_(umsg)("LL miss rate:  %s (%s     + %s  )\n", buf1, buf2,buf3);
+      VG_(umsg)("LL miss rate:  %*.1f%% (%*.1f%%     + %*.1f%%  )\n",
+                l1, LL_total_m  * 100.0 / (Ir_total.a + D_total.a),
+                l2, LL_total_mr * 100.0 / (Ir_total.a + Dr_total.a),
+                l3, LL_total_mw * 100.0 / Dw_total.a);
    }
 
    /* If branch profiling is enabled, show branch overall results. */
@@ -1675,11 +1672,10 @@ static void cg_fini(Int exitcode)
       VG_(umsg)(fmt, "Mispredicts:  ",
                      B_total.mp, Bc_total.mp, Bi_total.mp);
 
-      VG_(percentify)(B_total.mp,  B_total.b,  1, l1+1, buf1);
-      VG_(percentify)(Bc_total.mp, Bc_total.b, 1, l2+1, buf2);
-      VG_(percentify)(Bi_total.mp, Bi_total.b, 1, l3+1, buf3);
-
-      VG_(umsg)("Mispred rate:  %s (%s     + %s   )\n", buf1, buf2,buf3);
+      VG_(umsg)("Mispred rate:  %*.1f%% (%*.1f%%     + %*.1f%%   )\n",
+                l1, B_total.mp  * 100.0 / B_total.b,
+                l2, Bc_total.mp * 100.0 / Bc_total.b,
+                l3, Bi_total.mp * 100.0 / Bi_total.b);
    }
 
    // Various stats
@@ -1695,18 +1691,14 @@ static void cg_fini(Int exitcode)
       VG_(dmsg)("cachegrind: distinct instrs Gen: %d\n", distinct_instrsGen);
       VG_(dmsg)("cachegrind: debug lookups      : %d\n", debug_lookups);
       
-      VG_(percentify)(full_debugs,      debug_lookups, 1, 6, buf1);
-      VG_(percentify)(file_line_debugs, debug_lookups, 1, 6, buf2);
-      VG_(percentify)(fn_debugs,        debug_lookups, 1, 6, buf3);
-      VG_(percentify)(no_debugs,        debug_lookups, 1, 6, buf4);
-      VG_(dmsg)("cachegrind: with full      info:%s (%d)\n", 
-                buf1, full_debugs);
-      VG_(dmsg)("cachegrind: with file/line info:%s (%d)\n", 
-                buf2, file_line_debugs);
-      VG_(dmsg)("cachegrind: with fn name   info:%s (%d)\n", 
-                buf3, fn_debugs);
-      VG_(dmsg)("cachegrind: with zero      info:%s (%d)\n", 
-                buf4, no_debugs);
+      VG_(dmsg)("cachegrind: with full      info:%6.1f%% (%d)\n", 
+                full_debugs * 100.0 / debug_lookups, full_debugs);
+      VG_(dmsg)("cachegrind: with file/line info:%6.1f%% (%d)\n", 
+                file_line_debugs * 100.0 / debug_lookups, file_line_debugs);
+      VG_(dmsg)("cachegrind: with fn name   info:%6.1f%% (%d)\n", 
+                fn_debugs * 100.0 / debug_lookups, fn_debugs);
+      VG_(dmsg)("cachegrind: with zero      info:%6.1f%% (%d)\n", 
+                no_debugs * 100.0 / debug_lookups, no_debugs);
 
       VG_(dmsg)("cachegrind: string table size: %lu\n",
                 VG_(OSetGen_Size)(stringTable));
diff --git a/callgrind/main.c b/callgrind/main.c
index 740213123..0180ec649 100644
--- a/callgrind/main.c
+++ b/callgrind/main.c
@@ -1775,7 +1775,6 @@ static UInt ULong_width(ULong n)
 static
 void branchsim_printstat(int l1, int l2, int l3)
 {
-    static HChar buf1[128], buf2[128], buf3[128];
     static HChar fmt[128];    // large enough
     FullCost total;
     ULong Bc_total_b, Bc_total_mp, Bi_total_b, Bi_total_mp;
@@ -1803,11 +1802,10 @@ void branchsim_printstat(int l1, int l2, int l3)
     VG_(umsg)(fmt, "Mispredicts:  ",
               B_total_mp, Bc_total_mp, Bi_total_mp);
 
-    VG_(percentify)(B_total_mp,  B_total_b,  1, l1+1, buf1);
-    VG_(percentify)(Bc_total_mp, Bc_total_b, 1, l2+1, buf2);
-    VG_(percentify)(Bi_total_mp, Bi_total_b, 1, l3+1, buf3);
-
-    VG_(umsg)("Mispred rate:  %s (%s     + %s   )\n", buf1, buf2,buf3);
+    VG_(umsg)("Mispred rate:  %*.1f%% (%*.1f%%     + %*.1f%%   )\n",
+              l1, B_total_mp  * 100.0 / B_total_b,
+              l2, Bc_total_mp * 100.0 / Bc_total_b,
+              l3, Bi_total_mp * 100.0 / Bi_total_b);
 }
 
 static
diff --git a/coregrind/m_debuglog.c b/coregrind/m_debuglog.c
index 5ae2a5df1..47a27500f 100644
--- a/coregrind/m_debuglog.c
+++ b/coregrind/m_debuglog.c
@@ -1,3 +1,4 @@
+/* -*- mode: C; c-basic-offset: 3; -*- */
 
 /*--------------------------------------------------------------------*/
 /*--- Debug (not-for-user) logging; also vprintf.     m_debuglog.c ---*/
@@ -730,7 +731,7 @@ VG_(debugLog_vprintf) (
    UInt ret = 0;
    Int  i;
    Int  flags;
-   Int  width;
+   Int  width, precision;
    Int  n_ls = 0;
    Bool is_long, caps;
 
@@ -758,6 +759,7 @@ VG_(debugLog_vprintf) (
       flags = 0;
       n_ls  = 0;
       width = 0; /* length of the field. */
+      precision = -1;  /* unspecified precision */
       while (1) {
          switch (format[i]) {
          case '(':
@@ -787,9 +789,29 @@ VG_(debugLog_vprintf) (
       }
      parse_fieldwidth:
       /* Compute the field length. */
-      while (format[i] >= '0' && format[i] <= '9') {
-         width *= 10;
-         width += format[i++] - '0';
+      if (format[i] == '*') {
+         width = va_arg(vargs, Int);
+         ++i;
+      } else {
+         while (format[i] >= '0' && format[i] <= '9') {
+            width *= 10;
+            width += format[i++] - '0';
+         }
+      }
+      /* Parse precision, if any. Only meaningful for %f. For all other
+         format specifiers the precision will be silently ignored. */
+      if (format[i] == '.') {
+         ++i;
+         if (format[i] == '*') {
+            precision = va_arg(vargs, Int);
+            ++i;
+         } else {
+            precision = 0;
+            while (format[i] >= '0' && format[i] <= '9') {
+               precision *= 10;
+               precision += format[i++] - '0';
+            }
+         }
       }
       while (format[i] == 'l') {
          i++;
@@ -888,6 +910,96 @@ VG_(debugLog_vprintf) (
                                  flags, width, str, format[i]=='S');
             break;
          }
+         case 'f': {
+            /* Print a floating point number in the format x.y without
+               any exponent. Capabilities are extremely limited, basically
+               a joke, but good enough for our needs. */
+            Double val = va_arg (vargs, Double);
+            Bool is_negative = False;
+            Int cnt;
+
+            if (val < 0.0) {
+               is_negative = True;
+               val = - val;
+            }
+            /* If the integral part of the floating point number cannot be
+               represented by an ULONG_MAX, print '*' characters */
+            if (val > (Double)(~0ULL)) {
+               if (width == 0) width = 6;    // say
+               for (cnt = 0; cnt < width; ++cnt)
+                  send('*', send_arg2);
+               ret += width;
+               break;
+            }
+            /* The integral part of the floating point number is representable
+               by an ULong. */
+            ULong ipval = val;
+            Double frac = val - ipval;
+
+            if (precision == -1) precision = 6;   // say
+
+            /* Silently limit the precision to 10 digits. */
+            if (precision > 10) precision = 10;
+
+            /* If fracional part is not printed (precision == 0), may have to
+               round up */
+            if (precision == 0 && frac >= 0.5)
+               ipval += 1;
+
+            /* Find out how many characters are needed to print the number */
+
+            /* The integral part... */
+            UInt ipwidth, num_digit = 1;   // at least one digit
+            ULong x, old_x = 0;
+            for (x = 10; ; old_x = x, x *= 10, ++num_digit) {
+               if (x <= old_x) break;    // overflow occurred
+               if (ipval < x) break;
+            }
+            ipwidth = num_digit;   // width of integral part.
+            if (is_negative) ++num_digit;
+            if (precision != 0)
+               num_digit += 1 + precision;
+
+            // Print the number
+
+            // Fill in blanks on the left
+            if (num_digit < width && (flags & VG_MSG_LJUSTIFY) == 0) {
+               for (cnt = 0; cnt < width - num_digit; ++cnt)
+                  send(' ', send_arg2);
+               ret += width - num_digit;
+            }
+            // Sign, maybe
+            if (is_negative) {
+               send('-', send_arg2);
+               ret += 1;
+            }
+            // Integral part
+            ret += myvprintf_int64(send, send_arg2, 0, 10, ipwidth, False,
+                                   ipval);
+            // Decimal point and fractional part
+            if (precision != 0) {
+               send('.', send_arg2);
+               ret += 1;
+
+               // Fractional part
+               ULong factor = 1;
+               for (cnt = 0; cnt < precision; ++cnt)
+                  factor *= 10;
+               ULong frval = frac * factor;
+               if ((frac * factor - frval) > 0.5)    // round up
+                  frval += 1;
+               frval %= factor;
+               ret += myvprintf_int64(send, send_arg2, VG_MSG_ZJUSTIFY, 10,
+                                      precision, False, frval);
+            }
+            // Fill in blanks on the right
+            if (num_digit < width && (flags & VG_MSG_LJUSTIFY) != 0) {
+               for (cnt = 0; cnt < width - num_digit; ++cnt)
+                  send(' ', send_arg2);
+               ret += width - num_digit;
+            }
+            break;
+         }
 
 //         case 'y': { /* %y - print symbol */
 //            Addr a = va_arg(vargs, Addr);
diff --git a/coregrind/m_libcprint.c b/coregrind/m_libcprint.c
index 3617c039a..fbd3d4c4b 100644
--- a/coregrind/m_libcprint.c
+++ b/coregrind/m_libcprint.c
@@ -362,58 +362,6 @@ void VG_(fclose)( VgFile *fp )
    VG_(free)(fp);
 }
 
-/* ---------------------------------------------------------------------
-   percentify()
-   ------------------------------------------------------------------ */
-
-// Percentify n/m with d decimal places.  Includes the '%' symbol at the end.
-// Right justifies in 'buf'.
-void VG_(percentify)(ULong n, ULong m, UInt d, Int n_buf, HChar buf[]) 
-{
-   Int i, len, space;
-   ULong p1;
-   HChar fmt[32];   // large enough
-
-   if (m == 0) {
-      // Have to generate the format string in order to be flexible about
-      // the width of the field.
-      VG_(sprintf)(fmt, "%%%ds", n_buf);
-      // fmt is now "%<n_buf>s" where <d> is 1,2,3...
-      VG_(sprintf)(buf, fmt, "--%");
-      return;
-   }
-   
-   p1 = (100*n) / m;
-    
-   if (d == 0) {
-      VG_(sprintf)(buf, "%llu%%", p1);  // FIXME: unsafe
-   } else {
-      ULong p2;
-      UInt  ex;
-      switch (d) {
-      case 1: ex = 10;    break;
-      case 2: ex = 100;   break;
-      case 3: ex = 1000;  break;
-      default: VG_(core_panic)("Currently can only handle 3 decimal places");
-      }
-      p2 = ((100*n*ex) / m) % ex;
-      // Have to generate the format string in order to be flexible about
-      // the width of the post-decimal-point part.
-      VG_(sprintf)(fmt, "%%llu.%%0%ullu%%%%", d);
-      // fmt is now "%llu.%0<d>llu%%" where <d> is 1,2,3...
-      VG_(sprintf)(buf, fmt, p1, p2);   // FIXME: unsafe
-   }
-
-   len = VG_(strlen)(buf);
-   space = n_buf - len;
-   if (space < 0) space = 0;     /* Allow for v. small field_width */
-   i = len;
-
-   /* Right justify in field */
-   for (     ; i >= 0;    i--)  buf[i + space] = buf[i];
-   for (i = 0; i < space; i++)  buf[i] = ' ';
-}
-
 
 /* ---------------------------------------------------------------------
    elapsed_wallclock_time()
diff --git a/coregrind/m_sbprofile.c b/coregrind/m_sbprofile.c
index 0be07dd9c..7ed995090 100644
--- a/coregrind/m_sbprofile.c
+++ b/coregrind/m_sbprofile.c
@@ -50,7 +50,6 @@ void show_SB_profile ( const SBProfEntry tops[], UInt n_tops,
                        ULong score_total, ULong ecs_done )
 {
    ULong score_cumul, score_cumul_saved, score_here;
-   HChar buf_cumul[10], buf_here[10];
    Int   r; /* must be signed */
 
    HChar ecs_txt[50];
@@ -89,12 +88,18 @@ void show_SB_profile ( const SBProfEntry tops[], UInt n_tops,
 
       score_here = tops[r].score;
       score_cumul += score_here;
-      VG_(percentify)(score_cumul, score_total, 2, 6, buf_cumul);
-      VG_(percentify)(score_here,  score_total, 2, 6, buf_here);
-      VG_(printf)("%3d: (%9lld %s)   %9lld %s      0x%llx %s\n",
+
+      /* Careful: do not divide by zero. score_total == 0 implies
+         score_cumul == 0 and also score_here == 0. */
+      Double percent_cumul =
+         score_total == 0 ? 100.0 : score_cumul * 100.0 / score_total;
+      Double percent_here =
+         score_total == 0 ? 100.0 : score_here * 100.0 / score_total;
+        
+      VG_(printf)("%3d: (%9lld %5.2f%%)   %9lld %5.2f%%      0x%llx %s\n",
                   r,
-                  score_cumul, buf_cumul,
-                  score_here,  buf_here, tops[r].addr, name );
+                  score_cumul, percent_cumul,
+                  score_here,  percent_here, tops[r].addr, name);
    }
    score_cumul_saved = score_cumul;
 
@@ -122,15 +127,21 @@ void show_SB_profile ( const SBProfEntry tops[], UInt n_tops,
 
          score_here = tops[r].score;
          score_cumul += score_here;
-         VG_(percentify)(score_cumul, score_total, 2, 6, buf_cumul);
-         VG_(percentify)(score_here,  score_total, 2, 6, buf_here);
+
+         /* Careful: do not divide by zero. score_total == 0 implies
+            score_cumul == 0 and also score_here == 0. */
+         Double percent_cumul =
+           score_total == 0 ? 100.0 : score_cumul * 100.0 / score_total;
+         Double percent_here =
+           score_total == 0 ? 100.0 : score_here * 100.0 / score_total;
+
          VG_(printf)("\n");
          VG_(printf)("=-=-=-=-=-=-=-=-=-=-=-=-=-= begin SB rank %d "
                      "=-=-=-=-=-=-=-=-=-=-=-=-=-=\n\n", r);
-         VG_(printf)("%3d: (%9lld %s)   %9lld %s      0x%llx %s\n",
+         VG_(printf)("%3d: (%9lld %5.2f%%)   %9lld %5.2f%%      0x%llx %s\n",
                      r,
-                     score_cumul, buf_cumul,
-                     score_here,  buf_here, tops[r].addr, name );
+                     score_cumul, percent_cumul,
+                     score_here,  percent_here, tops[r].addr, name );
          VG_(printf)("\n");
          VG_(discard_translations)(tops[r].addr, 1, "bb profile");
          VG_(translate)(0, tops[r].addr, True, VG_(clo_profyle_flags), 0, True);
@@ -151,12 +162,18 @@ void show_SB_profile ( const SBProfEntry tops[], UInt n_tops,
          VG_(get_fnname_w_offset)(tops[r].addr, &name);
 
          score_here = tops[r].score;
-         VG_(percentify)(score_cumul, score_total, 2, 6, buf_cumul);
-         VG_(percentify)(score_here,  score_total, 2, 6, buf_here);
-         VG_(printf)("%3d: (%9lld %s)   %9lld %s      0x%llx %s\n",
+
+         /* Careful: do not divide by zero. score_total == 0 implies
+            score_cumul == 0 and also score_here == 0. */
+         Double percent_cumul =
+           score_total == 0 ? 100.0 : score_cumul * 100.0 / score_total;
+         Double percent_here =
+           score_total == 0 ? 100.0 : score_here * 100.0 / score_total;
+
+         VG_(printf)("%3d: (%9lld %5.2f%%)   %9lld %5.2f%%      0x%llx %s\n",
                      r,
-                     score_cumul, buf_cumul,
-                     score_here,  buf_here, tops[r].addr, name );
+                     score_cumul, percent_cumul,
+                     score_here,  percent_here, tops[r].addr, name );
          score_cumul -= score_here;
       }
       VG_(printf)("rank  ---cumulative---      -----self-----\n");
diff --git a/coregrind/m_translate.c b/coregrind/m_translate.c
index b5d10fbb2..816b5f265 100644
--- a/coregrind/m_translate.c
+++ b/coregrind/m_translate.c
@@ -73,23 +73,25 @@ static UInt n_SP_updates_generic_unknown = 0;
 
 void VG_(print_translation_stats) ( void )
 {
-   HChar buf[7];
    UInt n_SP_updates = n_SP_updates_fast + n_SP_updates_generic_known
                                          + n_SP_updates_generic_unknown;
-   VG_(percentify)(n_SP_updates_fast, n_SP_updates, 1, 6, buf);
+   if (n_SP_updates == 0) {
+      VG_(message)(Vg_DebugMsg, "translate: no SP updates identified\n");
+      return;
+   }
    VG_(message)(Vg_DebugMsg,
-      "translate:            fast SP updates identified: %'u (%s)\n",
-      n_SP_updates_fast, buf );
+      "translate:            fast SP updates identified: %'u (%3.1f%%)\n",
+      n_SP_updates_fast, n_SP_updates_fast * 100.0 / n_SP_updates );
 
-   VG_(percentify)(n_SP_updates_generic_known, n_SP_updates, 1, 6, buf);
    VG_(message)(Vg_DebugMsg,
-      "translate:   generic_known SP updates identified: %'u (%s)\n",
-      n_SP_updates_generic_known, buf );
+      "translate:   generic_known SP updates identified: %'u (%3.1f%%)\n",
+      n_SP_updates_generic_known,
+      n_SP_updates_generic_known * 100.0 / n_SP_updates );
 
-   VG_(percentify)(n_SP_updates_generic_unknown, n_SP_updates, 1, 6, buf);
    VG_(message)(Vg_DebugMsg,
-      "translate: generic_unknown SP updates identified: %'u (%s)\n",
-      n_SP_updates_generic_unknown, buf );
+      "translate: generic_unknown SP updates identified: %'u (%3.1f%%)\n",
+      n_SP_updates_generic_unknown,
+      n_SP_updates_generic_unknown * 100.0 / n_SP_updates );
 }
 
 /*------------------------------------------------------------*/
diff --git a/include/pub_tool_libcprint.h b/include/pub_tool_libcprint.h
index f71469a57..adfedb60f 100644
--- a/include/pub_tool_libcprint.h
+++ b/include/pub_tool_libcprint.h
@@ -63,11 +63,6 @@ extern UInt VG_(vsnprintf)( HChar* buf, Int size,
                                        const HChar *format, va_list vargs )
                           PRINTF_CHECK(3, 0);
 
-// Percentify n/m with d decimal places.  Includes the '%' symbol at the end.
-// Right justifies in 'buf'.
-extern void VG_(percentify)(ULong n, ULong m, UInt d, Int n_buf, HChar buf[]);
-
-
 /* ---------------------------------------------------------------------
    Output-printing functions
    ------------------------------------------------------------------ */
diff --git a/lackey/lk_main.c b/lackey/lk_main.c
index 485707c4f..b2ca1ff0e 100644
--- a/lackey/lk_main.c
+++ b/lackey/lk_main.c
@@ -997,10 +997,6 @@ IRSB* lk_instrument ( VgCallbackClosure* closure,
 
 static void lk_fini(Int exitcode)
 {
-   HChar percentify_buf[5]; /* Two digits, '%' and 0. */
-   const int percentify_size = sizeof(percentify_buf) - 1;
-   const int percentify_decs = 0;
-   
    tl_assert(clo_fnname);
    tl_assert(clo_fnname[0]);
 
@@ -1014,10 +1010,8 @@ static void lk_fini(Int exitcode)
       VG_(umsg)("\n");
       VG_(umsg)("Jccs:\n");
       VG_(umsg)("  total:         %'llu\n", total_Jccs);
-      VG_(percentify)(taken_Jccs, (total_Jccs ? total_Jccs : 1),
-         percentify_decs, percentify_size, percentify_buf);
-      VG_(umsg)("  taken:         %'llu (%s)\n",
-         taken_Jccs, percentify_buf);
+      VG_(umsg)("  taken:         %'llu (%.0f%%)\n",
+                taken_Jccs, taken_Jccs * 100.0 / total_Jccs ?: 1);
       
       VG_(umsg)("\n");
       VG_(umsg)("Executed:\n");
diff --git a/lackey/tests/true.stderr.exp b/lackey/tests/true.stderr.exp
index 9a1487587..0f1c3647c 100644
--- a/lackey/tests/true.stderr.exp
+++ b/lackey/tests/true.stderr.exp
@@ -4,7 +4,7 @@ Counted ... calls to main()
 
 Jccs:
   total:         ...
-  taken:         ... ( ...%)
+  taken:         ... (...%)
 
 Executed:
   SBs entered:   ...
diff --git a/massif/ms_main.c b/massif/ms_main.c
index 450379dd1..01daaf041 100644
--- a/massif/ms_main.c
+++ b/massif/ms_main.c
@@ -2105,18 +2105,6 @@ IRSB* ms_instrument ( VgCallbackClosure* closure,
 
 #define FP(format, args...) ({ VG_(fprintf)(fp, format, ##args); })
 
-// Nb: uses a static buffer, each call trashes the last string returned.
-static const HChar* make_perc(double x)
-{
-   static HChar mbuf[32];
-
-   VG_(percentify)((ULong)(x * 100), 10000, 2, 6, mbuf);
-   // XXX: this is bogus if the denominator was zero -- resulting string is
-   // something like "0 --%")
-   if (' ' == mbuf[0]) mbuf[0] = '0';
-   return mbuf;
-}
-
 static void pp_snapshot_SXPt(VgFile *fp, SXPt* sxpt, Int depth,
                              HChar* depth_str, Int depth_str_len,
                              SizeT snapshot_heap_szB, SizeT snapshot_total_szB)
@@ -2225,9 +2213,8 @@ static void pp_snapshot_SXPt(VgFile *fp, SXPt* sxpt, Int depth,
 
     case InsigSXPt: {
       const HChar* s = ( 1 == sxpt->Insig.n_xpts ? "," : "s, all" );
-      FP("%sn0: %lu in %d place%s below massif's threshold (%s)\n",
-         depth_str, sxpt->szB, sxpt->Insig.n_xpts, s,
-         make_perc(clo_threshold));
+      FP("%sn0: %lu in %d place%s below massif's threshold (%.2f%%)\n",
+         depth_str, sxpt->szB, sxpt->Insig.n_xpts, s, clo_threshold);
       break;
     }
 
diff --git a/massif/tests/insig.post.exp b/massif/tests/insig.post.exp
index 5963decfe..5a4abd5f1 100644
--- a/massif/tests/insig.post.exp
+++ b/massif/tests/insig.post.exp
@@ -70,7 +70,7 @@ Number of snapshots: 24
 87.28% (16,688B) (heap allocation functions) malloc/new/new[], --alloc-fns, etc.
 ->83.68% (16,000B) 0x........: main (insig.c:8)
 | 
-->01.34% (256B) in 16 places, all below massif's threshold (00.99%)
+->01.34% (256B) in 16 places, all below massif's threshold (0.99%)
 | 
 ->01.26% (240B) 0x........: main (insig.c:9)
 | 
diff --git a/massif/tests/thresholds_5_0.post.exp b/massif/tests/thresholds_5_0.post.exp
index b54bd88ef..96ee9df8d 100644
--- a/massif/tests/thresholds_5_0.post.exp
+++ b/massif/tests/thresholds_5_0.post.exp
@@ -52,7 +52,7 @@ Number of snapshots: 10
 | |   
 | ->05.00% (4,000B) 0x........: main (thresholds.c:54)
 | | 
-| ->01.50% (1,200B) in 2 places, all below massif's threshold (05.00%)
+| ->01.50% (1,200B) in 2 places, all below massif's threshold (5.00%)
 |   
 ->20.00% (16,000B) 0x........: main (thresholds.c:55)
 | 
@@ -60,7 +60,7 @@ Number of snapshots: 10
 | ->09.00% (7,200B) 0x........: a7550 (thresholds.c:39)
 | | ->09.00% (7,200B) 0x........: main (thresholds.c:52)
 | |   
-| ->04.00% (3,200B) in 2 places, all below massif's threshold (05.00%)
+| ->04.00% (3,200B) in 2 places, all below massif's threshold (5.00%)
 |   
-->00.50% (400B) in 1 place, below massif's threshold (05.00%)
+->00.50% (400B) in 1 place, below massif's threshold (5.00%)
   
diff --git a/massif/tests/zero1.post.exp b/massif/tests/zero1.post.exp
index db640cb67..cddd70ef0 100644
--- a/massif/tests/zero1.post.exp
+++ b/massif/tests/zero1.post.exp
@@ -46,7 +46,7 @@ Number of snapshots: 21
   8              0                0                0             0            0
   9              0                0                0             0            0
 00.00% (0B) (heap allocation functions) malloc/new/new[], --alloc-fns, etc.
-->00.00% (0B) in 5 places, all below massif's threshold (01.00%)
+->00.00% (0B) in 5 places, all below massif's threshold (1.00%)
   
 --------------------------------------------------------------------------------
   n        time(B)         total(B)   useful-heap(B) extra-heap(B)    stacks(B)
@@ -62,7 +62,7 @@ Number of snapshots: 21
  18              0                0                0             0            0
  19              0                0                0             0            0
 00.00% (0B) (heap allocation functions) malloc/new/new[], --alloc-fns, etc.
-->00.00% (0B) in 10 places, all below massif's threshold (01.00%)
+->00.00% (0B) in 10 places, all below massif's threshold (1.00%)
   
 --------------------------------------------------------------------------------
   n        time(B)         total(B)   useful-heap(B) extra-heap(B)    stacks(B)
diff --git a/memcheck/mc_main.c b/memcheck/mc_main.c
index 86a9574db..5cd241415 100644
--- a/memcheck/mc_main.c
+++ b/memcheck/mc_main.c
@@ -965,11 +965,9 @@ static void gcSecVBitTable(void)
    VG_(OSetGen_Destroy)(secVBitTable);
    secVBitTable = secVBitTable2;
 
-   if (VG_(clo_verbosity) > 1) {
-      HChar percbuf[7];
-      VG_(percentify)(n_survivors, n_nodes, 1, 6, percbuf);
-      VG_(message)(Vg_DebugMsg, "memcheck GC: %d nodes, %d survivors (%s)\n",
-                   n_nodes, n_survivors, percbuf);
+   if (VG_(clo_verbosity) > 1 && n_nodes != 0) {
+      VG_(message)(Vg_DebugMsg, "memcheck GC: %d nodes, %d survivors (%.1f%%)\n",
+                   n_nodes, n_survivors, n_survivors * 100.0 / n_nodes);
    }
 
    // Increase table size if necessary.
diff --git a/none/tests/Makefile.am b/none/tests/Makefile.am
index daa8c8ba4..b9a1767f7 100644
--- a/none/tests/Makefile.am
+++ b/none/tests/Makefile.am
@@ -175,6 +175,7 @@ EXTRA_DIST = \
 	threadederrno.vgtest \
 	timestamp.stderr.exp timestamp.vgtest \
 	tls.vgtest tls.stderr.exp tls.stdout.exp  \
+	unit_debuglog.stderr.exp unit_debuglog.vgtest \
 	vgprintf.stderr.exp vgprintf.vgtest \
 	process_vm_readv_writev.stderr.exp process_vm_readv_writev.vgtest
 
@@ -211,6 +212,7 @@ check_PROGRAMS = \
 	tls \
 	tls.so \
 	tls2.so \
+	unit_debuglog \
 	valgrind_cpp_test \
 	vgprintf \
 	coolo_sigaction \
diff --git a/none/tests/unit_debuglog.c b/none/tests/unit_debuglog.c
new file mode 100644
index 000000000..1fecb3031
--- /dev/null
+++ b/none/tests/unit_debuglog.c
@@ -0,0 +1,148 @@
+/* Test %f format specifier */
+#include <assert.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "pub_core_basics.h"
+#include "pub_core_libcbase.h"
+#include "pub_core_libcassert.h"
+#include "pub_core_libcprint.h"
+
+#undef vg_assert
+#define vg_assert(e)                   assert(e)
+#undef vg_assert2
+#define vg_assert2(e, fmt, args...)    assert(e)
+
+#include "coregrind/m_debuglog.c"
+
+void run(const char *format, ...)
+{
+  int n, num_stars, i1, i2;
+  const char *p;
+  printf_buf buf;
+  va_list vargs;
+
+  // Count number of '*' in format
+  num_stars = 0;
+  for (p = format; *p; ++p)
+    if (*p == '*') ++num_stars;
+
+  va_start(vargs, format);
+  fprintf(stderr, "%s\tprintf =   ", format);
+  switch (num_stars) {
+  case 0:
+    n = fprintf(stderr, format, va_arg(vargs, Double));
+    break;
+  case 1:
+    i1 = va_arg(vargs, int);
+    n = fprintf(stderr, format, i1, va_arg(vargs, Double));
+    break;
+  case 2:
+    i1 = va_arg(vargs, int);
+    i2 = va_arg(vargs, int);
+    n = fprintf(stderr, format, i1, i2, va_arg(vargs, Double));
+    break;
+  }
+  fprintf(stderr, "\twrote %3d chars\n", n);
+  va_end(vargs);
+
+  buf.n = 0;
+  buf.buf[0] = 0;
+
+  fprintf(stderr, "%s\tdebuglog = ", format);
+  va_start(vargs, format);
+  n = VG_(debugLog_vprintf)(add_to_buf, &buf, format, vargs);
+  va_end(vargs);
+
+  emit(buf.buf, strlen(buf.buf));
+  fprintf(stderr, "\twrote %3d chars\n", n);
+}
+
+
+int main(int argc, char *argv[])
+{
+  double value;
+
+  fprintf(stderr, "...testing value 0\n");
+  value = 0.0;
+  run("|%f|", value);
+  run("|%2f|", value);
+  run("|%9f|", value);
+  run("|%8.0f|", value);
+  run("|%8.1f|", value);
+  run("|%8.2f|", value);
+
+  fprintf(stderr, "\n");
+  fprintf(stderr, "...testing value 3.7  (with rounding)\n");
+  value = 3.7;
+  run("|%f|", value);
+  run("|%4f|", value);
+  run("|%9f|", value);
+  run("|%4.0f|", value);
+  run("|%4.1f|", value);
+  run("|%4.2f|", value);
+
+  fprintf(stderr, "\n");
+  fprintf(stderr, "...testing value 123.01\n");
+  value = 123.01;
+  run("|%f|", value);
+  run("|%4f|", value);
+  run("|%9f|", value);
+  run("|%8.0f|", value);
+  run("|%8.1f|", value);
+  run("|%8.2f|", value);
+  run("|%8.3f|", value);
+
+  fprintf(stderr, "\n");
+  fprintf(stderr, "...testing value 3.0019  (with rounding)\n");
+  value = 3.0019;
+  run("|%f|", value);
+  run("|%10f|", value);
+  run("|%10.0f|", value);
+  run("|%10.3f|", value);
+  run("|%10.4f|", value);
+  run("|%.4f|", value);
+  run("|%.9f|", value);
+
+  fprintf(stderr, "\n");
+  fprintf(stderr, "...testing value -123.456 (with rounding)\n");
+  value = -123.456;
+  run("|%f|", value);
+  run("|%10f|", value);
+  run("|%10.0f|", value);
+  run("|%10.1f|", value);
+  run("|%10.2f|", value);
+  run("|%10.3f|", value);
+  run("|%10.4f|", value);
+  run("|%10.5f|", value);
+  run("|%.4f|", value);
+
+  fprintf(stderr, "\n");
+  fprintf(stderr, "...testing value = -123.456 width = '*'\n");
+  value = -123.456;
+  run("|%*f|", 10, value);
+  run("|%*f|", 2, value);
+  run("|%*f.1|", 10, value);
+
+  fprintf(stderr, "\n");
+  fprintf(stderr, "...testing precision = '*'\n");
+  value = -123.456;
+  run("|%.*f|", 10, value);
+  run("|%.*f|", 2, value);
+  run("|%10.*f|", 2, value);
+
+  fprintf(stderr, "\n");
+  fprintf(stderr, "...testing width/precision = '*'\n");
+  value = -123.456;
+  run("|%*.*f|", 20, 5, value);
+  run("|%*.*f|", 1, 4, value);
+
+
+  fprintf(stderr, "\n");
+  fprintf(stderr, "...testing left justification\n");
+  value = 3.1415;
+  run("|%10f|", value);
+  run("|%-10f|", value);
+  return 0;
+}
diff --git a/none/tests/unit_debuglog.stderr.exp b/none/tests/unit_debuglog.stderr.exp
new file mode 100644
index 000000000..7e8e87ac8
--- /dev/null
+++ b/none/tests/unit_debuglog.stderr.exp
@@ -0,0 +1,107 @@
+...testing value 0
+|%f|	printf =   |0.000000|	wrote  10 chars
+|%f|	debuglog = |0.000000|	wrote  10 chars
+|%2f|	printf =   |0.000000|	wrote  10 chars
+|%2f|	debuglog = |0.000000|	wrote  10 chars
+|%9f|	printf =   | 0.000000|	wrote  11 chars
+|%9f|	debuglog = | 0.000000|	wrote  11 chars
+|%8.0f|	printf =   |       0|	wrote  10 chars
+|%8.0f|	debuglog = |       0|	wrote  10 chars
+|%8.1f|	printf =   |     0.0|	wrote  10 chars
+|%8.1f|	debuglog = |     0.0|	wrote  10 chars
+|%8.2f|	printf =   |    0.00|	wrote  10 chars
+|%8.2f|	debuglog = |    0.00|	wrote  10 chars
+
+...testing value 3.7  (with rounding)
+|%f|	printf =   |3.700000|	wrote  10 chars
+|%f|	debuglog = |3.700000|	wrote  10 chars
+|%4f|	printf =   |3.700000|	wrote  10 chars
+|%4f|	debuglog = |3.700000|	wrote  10 chars
+|%9f|	printf =   | 3.700000|	wrote  11 chars
+|%9f|	debuglog = | 3.700000|	wrote  11 chars
+|%4.0f|	printf =   |   4|	wrote   6 chars
+|%4.0f|	debuglog = |   4|	wrote   6 chars
+|%4.1f|	printf =   | 3.7|	wrote   6 chars
+|%4.1f|	debuglog = | 3.7|	wrote   6 chars
+|%4.2f|	printf =   |3.70|	wrote   6 chars
+|%4.2f|	debuglog = |3.70|	wrote   6 chars
+
+...testing value 123.01
+|%f|	printf =   |123.010000|	wrote  12 chars
+|%f|	debuglog = |123.010000|	wrote  12 chars
+|%4f|	printf =   |123.010000|	wrote  12 chars
+|%4f|	debuglog = |123.010000|	wrote  12 chars
+|%9f|	printf =   |123.010000|	wrote  12 chars
+|%9f|	debuglog = |123.010000|	wrote  12 chars
+|%8.0f|	printf =   |     123|	wrote  10 chars
+|%8.0f|	debuglog = |     123|	wrote  10 chars
+|%8.1f|	printf =   |   123.0|	wrote  10 chars
+|%8.1f|	debuglog = |   123.0|	wrote  10 chars
+|%8.2f|	printf =   |  123.01|	wrote  10 chars
+|%8.2f|	debuglog = |  123.01|	wrote  10 chars
+|%8.3f|	printf =   | 123.010|	wrote  10 chars
+|%8.3f|	debuglog = | 123.010|	wrote  10 chars
+
+...testing value 3.0019  (with rounding)
+|%f|	printf =   |3.001900|	wrote  10 chars
+|%f|	debuglog = |3.001900|	wrote  10 chars
+|%10f|	printf =   |  3.001900|	wrote  12 chars
+|%10f|	debuglog = |  3.001900|	wrote  12 chars
+|%10.0f|	printf =   |         3|	wrote  12 chars
+|%10.0f|	debuglog = |         3|	wrote  12 chars
+|%10.3f|	printf =   |     3.002|	wrote  12 chars
+|%10.3f|	debuglog = |     3.002|	wrote  12 chars
+|%10.4f|	printf =   |    3.0019|	wrote  12 chars
+|%10.4f|	debuglog = |    3.0019|	wrote  12 chars
+|%.4f|	printf =   |3.0019|	wrote   8 chars
+|%.4f|	debuglog = |3.0019|	wrote   8 chars
+|%.9f|	printf =   |3.001900000|	wrote  13 chars
+|%.9f|	debuglog = |3.001900000|	wrote  13 chars
+
+...testing value -123.456 (with rounding)
+|%f|	printf =   |-123.456000|	wrote  13 chars
+|%f|	debuglog = |-123.456000|	wrote  13 chars
+|%10f|	printf =   |-123.456000|	wrote  13 chars
+|%10f|	debuglog = |-123.456000|	wrote  13 chars
+|%10.0f|	printf =   |      -123|	wrote  12 chars
+|%10.0f|	debuglog = |      -123|	wrote  12 chars
+|%10.1f|	printf =   |    -123.5|	wrote  12 chars
+|%10.1f|	debuglog = |    -123.5|	wrote  12 chars
+|%10.2f|	printf =   |   -123.46|	wrote  12 chars
+|%10.2f|	debuglog = |   -123.46|	wrote  12 chars
+|%10.3f|	printf =   |  -123.456|	wrote  12 chars
+|%10.3f|	debuglog = |  -123.456|	wrote  12 chars
+|%10.4f|	printf =   | -123.4560|	wrote  12 chars
+|%10.4f|	debuglog = | -123.4560|	wrote  12 chars
+|%10.5f|	printf =   |-123.45600|	wrote  12 chars
+|%10.5f|	debuglog = |-123.45600|	wrote  12 chars
+|%.4f|	printf =   |-123.4560|	wrote  11 chars
+|%.4f|	debuglog = |-123.4560|	wrote  11 chars
+
+...testing value = -123.456 width = '*'
+|%*f|	printf =   |-123.456000|	wrote  13 chars
+|%*f|	debuglog = |-123.456000|	wrote  13 chars
+|%*f|	printf =   |-123.456000|	wrote  13 chars
+|%*f|	debuglog = |-123.456000|	wrote  13 chars
+|%*f.1|	printf =   |-123.456000.1|	wrote  15 chars
+|%*f.1|	debuglog = |-123.456000.1|	wrote  15 chars
+
+...testing precision = '*'
+|%.*f|	printf =   |-123.4560000000|	wrote  17 chars
+|%.*f|	debuglog = |-123.4560000000|	wrote  17 chars
+|%.*f|	printf =   |-123.46|	wrote   9 chars
+|%.*f|	debuglog = |-123.46|	wrote   9 chars
+|%10.*f|	printf =   |   -123.46|	wrote  12 chars
+|%10.*f|	debuglog = |   -123.46|	wrote  12 chars
+
+...testing width/precision = '*'
+|%*.*f|	printf =   |          -123.45600|	wrote  22 chars
+|%*.*f|	debuglog = |          -123.45600|	wrote  22 chars
+|%*.*f|	printf =   |-123.4560|	wrote  11 chars
+|%*.*f|	debuglog = |-123.4560|	wrote  11 chars
+
+...testing left justification
+|%10f|	printf =   |  3.141500|	wrote  12 chars
+|%10f|	debuglog = |  3.141500|	wrote  12 chars
+|%-10f|	printf =   |3.141500  |	wrote  12 chars
+|%-10f|	debuglog = |3.141500  |	wrote  12 chars
diff --git a/none/tests/unit_debuglog.vgtest b/none/tests/unit_debuglog.vgtest
new file mode 100644
index 000000000..1caaaf531
--- /dev/null
+++ b/none/tests/unit_debuglog.vgtest
@@ -0,0 +1,2 @@
+prog: unit_debuglog
+vgopts: -q