On Wed, 2011-08-31 at 16:25 +0400, Dmitry V. Levin wrote:
> On Wed, Aug 31, 2011 at 02:04:52PM +0200, Denys Vlasenko wrote:
> > On Tue, 2011-08-30 at 20:20 +0400, Dmitry V. Levin wrote:
> > > On Wed, Aug 24, 2011 at 11:41:10PM +0000, Denys Vlasenko wrote:
> > > > commit 102ec4935440ff52a7fa3566154a84cc2473f16a
> > > > Author: Denys Vlasenko <[email protected]>
> > > > Date: Thu Aug 25 01:27:59 2011 +0200
> > > >
> > > > Optimize tabto()
> > > >
> > > > tabto is used in many lines of strace output.
> > > > On glibc, tprintf("%*s", col - curcol, "") is noticeably slow
> > > > compared to tprintf(" "). Use the latter.
> > > > Observed ~15% reduction of time spent in userspace.
> > > >
> > > > * defs.h: Drop extern declaration of acolumn. Make tabto()
> > > > take no parameters.
> > > > * process.c (sys_exit): Call tabto() with no parameters.
> > > > * syscall.c (trace_syscall_exiting): Call tabto() with no
> > > > parameters.
> > > > * strace.c: Make acolumn static, add static char *acolumn_spaces.
> > > > (main): Allocate acolumn_spaces as a string of spaces.
> > > > (printleader): Call tabto() with no parameters.
> > > > (tabto): Use simpler method to print lots of spaces.
> > > [...]
> > > > void
> > > > -tabto(int col)
> > > > +tabto(void)
> > > > {
> > > > - if (curcol < col)
> > > > - tprintf("%*s", col - curcol, "");
> > > > + if (curcol < acolumn)
> > > > + tprintf(acolumn_spaces + curcol);
> > > > }
> > >
> > > The new statement yields a warning:
> > >
> > > strace.c: In function 'tabto':
> > > strace.c:2701:3: warning: format not a string literal and no format
> > > arguments
> >
> > Pity, my toolchain doesn't emit that... I can't detect these warnings.
>
> My toolchain enables -Wformat-security by default. We can get it enabled
> by default in strace by adding gl_WARN_ADD([-Wformat-security]) to
> configure.ac
>
> > > Maybe we could use
> > > tprintf("%s", acolumn_spaces + curcol);
> > > instead without performance degradation?
> >
> > There will be some performance degradation.
> > Is there a way to suppress this warning on a case-by-case basis?
>
> I'm not aware of such a way. If the performance degradation is
> noticeable, a straightforward function tprint_str(const char *str) could
> be added to do exactly that. The implementation could use fputs() instead
> of vfprintf(), and that would speedup things even more than now. ;)
Something like this?
--
vda
diff -d -urpN strace.4/defs.h strace.5/defs.h
--- strace.4/defs.h 2011-08-31 13:53:17.000000000 +0200
+++ strace.5/defs.h 2011-08-31 15:04:13.625365787 +0200
@@ -708,6 +708,7 @@ extern int proc_open(struct tcb *tcp, in
printtv_bitness((tcp), (addr), BITNESS_CURRENT, 1)
extern void tprintf(const char *fmt, ...) __attribute__ ((format (printf, 1,
2)));
+extern void tprints(const char *str);
#ifndef HAVE_STRERROR
const char *strerror(int);
diff -d -urpN strace.4/desc.c strace.5/desc.c
--- strace.4/desc.c 2011-08-31 13:53:17.000000000 +0200
+++ strace.5/desc.c 2011-08-31 15:05:22.492264800 +0200
@@ -519,7 +519,7 @@ decode_select(struct tcb *tcp, long *arg
tprintf(", [");
for (j = 0, sep = ""; j < nfds; j++) {
if (FD_ISSET(j, fds)) {
- tprintf("%s", sep);
+ tprints(sep);
printfd(tcp, j);
sep = " ";
}
diff -d -urpN strace.4/file.c strace.5/file.c
--- strace.4/file.c 2011-08-31 13:53:17.000000000 +0200
+++ strace.5/file.c 2011-08-31 15:05:30.699367714 +0200
@@ -386,7 +386,7 @@ sprint_open_modes(mode_t flags)
void
tprint_open_modes(mode_t flags)
{
- tprintf("%s", sprint_open_modes(flags) + sizeof("flags"));
+ tprints(sprint_open_modes(flags) + sizeof("flags"));
}
static int
diff -d -urpN strace.4/io.c strace.5/io.c
--- strace.4/io.c 2011-08-31 10:47:35.000000000 +0200
+++ strace.5/io.c 2011-08-31 15:05:42.332513580 +0200
@@ -426,7 +426,7 @@ sys_ioctl(struct tcb *tcp)
tprintf(", ");
iop = ioctl_lookup(tcp->u_arg[1]);
if (iop) {
- tprintf("%s", iop->symbol);
+ tprints(iop->symbol);
while ((iop = ioctl_next_match(iop)))
tprintf(" or %s", iop->symbol);
} else
diff -d -urpN strace.4/net.c strace.5/net.c
--- strace.4/net.c 2011-08-31 10:47:35.000000000 +0200
+++ strace.5/net.c 2011-08-31 15:05:54.317663846 +0200
@@ -1468,7 +1468,7 @@ tprint_sock_type(struct tcb *tcp, int fl
const char *str = xlookup(socktypes, flags & SOCK_TYPE_MASK);
if (str) {
- tprintf("%s", str);
+ tprints(str);
flags &= ~SOCK_TYPE_MASK;
if (!flags)
return;
diff -d -urpN strace.4/process.c strace.5/process.c
--- strace.4/process.c 2011-08-31 10:47:35.000000000 +0200
+++ strace.5/process.c 2011-08-31 15:16:51.807428788 +0200
@@ -1505,7 +1505,7 @@ printargv(struct tcb *tcp, long addr)
cp.p64 = cp.p32;
if (cp.p64 == 0)
break;
- tprintf("%s", sep);
+ tprints(sep);
printstr(tcp, cp.p64, -1);
addr += personality_wordsize[current_personality];
}
diff -d -urpN strace.4/signal.c strace.5/signal.c
--- strace.4/signal.c 2011-08-31 10:47:35.000000000 +0200
+++ strace.5/signal.c 2011-08-31 15:07:43.118027310 +0200
@@ -385,13 +385,13 @@ sprintsigmask(const char *str, sigset_t
static void
printsigmask(sigset_t *mask, int rt)
{
- tprintf("%s", sprintsigmask("", mask, rt));
+ tprints(sprintsigmask("", mask, rt));
}
void
printsignal(int nr)
{
- tprintf("%s", signame(nr));
+ tprints(signame(nr));
}
void
diff -d -urpN strace.4/strace.c strace.5/strace.c
--- strace.4/strace.c 2011-08-31 13:59:59.000000000 +0200
+++ strace.5/strace.c 2011-08-31 15:12:57.125956341 +0200
@@ -2646,7 +2646,21 @@ tprintf(const char *fmt, ...)
curcol += n;
}
va_end(args);
- return;
+}
+
+void
+tprints(const char *str)
+{
+ if (outf) {
+ int n = fputs(str, outf);
+ if (n >= 0) {
+ curcol += strlen(str);
+ return;
+ }
+ if (outf != stderr)
+ perror(outfname == NULL
+ ? "<writing to pipe>" : outfname);
+ }
}
void
@@ -2705,7 +2719,7 @@ void
tabto(void)
{
if (curcol < acolumn)
- tprintf(acolumn_spaces + curcol);
+ tprints(acolumn_spaces + curcol);
}
void
diff -d -urpN strace.4/stream.c strace.5/stream.c
--- strace.4/stream.c 2011-08-31 12:26:01.000000000 +0200
+++ strace.5/stream.c 2011-08-31 15:13:28.999354690 +0200
@@ -742,17 +742,17 @@ print_transport_message(struct tcb *tcp,
#define GET(type, struct) \
do { \
if (len < sizeof m.struct) goto dump; \
- if (umove(tcp, addr, &m.struct) < 0) goto dump;\
- tprintf("{"); \
+ if (umove(tcp, addr, &m.struct) < 0) goto dump; \
+ tprints("{"); \
if (expect != type) { \
++c; \
- tprintf(#type); \
+ tprints(#type); \
} \
} \
while (0)
#define COMMA() \
- do { if (c++) tprintf(", "); } while (0)
+ do { if (c++) tprints(", "); } while (0)
#define STRUCT(struct, elem, print) \
@@ -767,7 +767,7 @@ print_transport_message(struct tcb *tcp,
m.struct.elem##_offset); \
} \
else { \
- tprintf(#elem "="); \
+ tprints(#elem "="); \
print(tcp, \
addr + m.struct.elem##_offset, \
m.struct.elem##_length); \
diff -d -urpN strace.4/syscall.c strace.5/syscall.c
--- strace.4/syscall.c 2011-08-31 13:53:17.000000000 +0200
+++ strace.5/syscall.c 2011-08-31 15:05:59.004722609 +0200
@@ -683,7 +683,7 @@ sys_indir(struct tcb *tcp)
return 0;
}
nargs = sysent[scno].nargs;
- tprintf("%s", sysent[scno].sys_name);
+ tprints(sysent[scno].sys_name);
for (i = 0; i < nargs; i++)
tprintf(", %#lx", tcp->u_arg[i+1]);
}
diff -d -urpN strace.4/util.c strace.5/util.c
--- strace.4/util.c 2011-08-31 13:53:17.000000000 +0200
+++ strace.5/util.c 2011-08-31 15:16:51.808428798 +0200
@@ -236,7 +236,7 @@ printxval(const struct xlat *xlat, int v
const char *str = xlookup(xlat, val);
if (str)
- tprintf("%s", str);
+ tprints(str);
else
tprintf("%#x /* %s */", val, dflt);
}
@@ -340,7 +340,7 @@ printflags(const struct xlat *xlat, int
const char *sep;
if (flags == 0 && xlat->val == 0) {
- tprintf("%s", xlat->str);
+ tprints(xlat->str);
return 1;
}
@@ -423,8 +423,7 @@ printfd(struct tcb *tcp, int fd)
void
printuid(const char *text, unsigned long uid)
{
- tprintf("%s", text);
- tprintf((uid == -1) ? "%ld" : "%lu", uid);
+ tprintf((uid == -1) ? "%s%ld" : "%s%lu", text, uid);
}
static char path[MAXPATHLEN + 1];
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