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Message-ID: <20131001113456.GA31331@gmail.com>
Date: Tue, 1 Oct 2013 13:34:56 +0200
From: Ingo Molnar <mingo@...nel.org>
To: Arnaldo Carvalho de Melo <acme@...stprotocols.net>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>,
David Ahern <dsahern@...il.com>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
Peter Zijlstra <a.p.zijlstra@...llo.nl>,
Thomas Gleixner <tglx@...utronix.de>,
Andrew Morton <akpm@...ux-foundation.org>,
Jiri Olsa <jolsa@...hat.com>, Namhyung Kim <namhyung@...il.com>
Subject: [PATCH] perf autodep: Remove strlcpy feature check, add __weak
strlcpy implementation
* Ingo Molnar <mingo@...nel.org> wrote:
> > > > Checking why that strlcpy failed...
> > >
> > > I don't think glibc does strlcpy. It's not a standard C function,
> > > and
> >
> > My concern was more about the thinking: ``Is this red "OFF" thing a
> > problem? I feel so much more confortable when all entries have nice
> > green "on" lights...''
>
> Yeah, so I think we should add our internal implementation of strlcpy()
> as a __weak function instead - if the libc does not provide then we
> provide a fallback.
>
> That should get rid of another ~50 msecs of build overhead, as failed
> feature tests are the most expensive ones.
The patch below implements that. I haven't actually tested it on a system
with a in-libc strlcpy implementation, but it Should Just Work (tm) ;-)
Overhead is down from 0.600 secs to 0.540 secs. The only remaining thing
is the libperl bug, I'll have a look at that next.
( I also couldn't resist fixing up perf's version of compiler.h a bit,
will split that out into a separate patch later on. )
Thanks,
Ingo
=====================>
Subject: perf autodep: Remove strlcpy feature check, add __weak strlcpy implementation
From: Ingo Molnar <mingo@...nel.org>
Date: Tue Oct 1 13:26:13 CEST 2013
---
tools/perf/config/Makefile | 8 +-------
tools/perf/config/feature-checks/Makefile | 3 ---
tools/perf/config/feature-checks/test-strlcpy.c | 8 --------
tools/perf/util/cache.h | 3 +--
tools/perf/util/include/linux/compiler.h | 19 ++++++++++++++-----
tools/perf/util/path.c | 10 +++++++---
6 files changed, 23 insertions(+), 28 deletions(-)
Index: tip/tools/perf/config/Makefile
===================================================================
--- tip.orig/tools/perf/config/Makefile
+++ tip/tools/perf/config/Makefile
@@ -101,7 +101,7 @@ $(info )
$(info Auto-detecting system features:)
$(shell make -i -j -C config/feature-checks >/dev/null 2>&1)
-FEATURE_TESTS = stackprotector-all volatile-register-var fortify-source libelf libelf-mmap glibc dwarf libelf-getphdrnum libunwind libaudit libslang gtk2 gtk2-infobar libperl libpython libpython-version libbfd strlcpy on-exit backtrace libnuma
+FEATURE_TESTS = stackprotector-all volatile-register-var fortify-source libelf libelf-mmap glibc dwarf libelf-getphdrnum libunwind libaudit libslang gtk2 gtk2-infobar libperl libpython libpython-version libbfd on-exit backtrace libnuma
$(foreach feat,$(FEATURE_TESTS),$(call feature_check,$(feat)))
@@ -421,12 +421,6 @@ else
endif
endif
-ifndef NO_STRLCPY
- ifeq ($(feature-strlcpy), 1)
- CFLAGS += -DHAVE_STRLCPY_SUPPORT
- endif
-endif
-
ifndef NO_ON_EXIT
ifeq ($(feature-on-exit), 1)
CFLAGS += -DHAVE_ON_EXIT_SUPPORT
Index: tip/tools/perf/config/feature-checks/Makefile
===================================================================
--- tip.orig/tools/perf/config/feature-checks/Makefile
+++ tip/tools/perf/config/feature-checks/Makefile
@@ -93,9 +93,6 @@ test-libpython-version: test-libpython-v
test-libbfd: test-libbfd.c
$(CC) -o $@ $@.c -DPACKAGE='perf' -DPACKAGE=perf -lbfd -ldl
-test-strlcpy: test-strlcpy.c
- $(CC) -o $@ $@.c
-
test-on-exit: test-on-exit.c
$(CC) -o $@ $@.c
Index: tip/tools/perf/config/feature-checks/test-strlcpy.c
===================================================================
--- tip.orig/tools/perf/config/feature-checks/test-strlcpy.c
+++ /dev/null
@@ -1,8 +0,0 @@
-#include <stdlib.h>
-extern size_t strlcpy(char *dest, const char *src, size_t size);
-
-int main(void)
-{
- strlcpy(NULL, NULL, 0);
- return 0;
-}
Index: tip/tools/perf/util/cache.h
===================================================================
--- tip.orig/tools/perf/util/cache.h
+++ tip/tools/perf/util/cache.h
@@ -70,8 +70,7 @@ extern char *perf_path(const char *fmt,
extern char *perf_pathdup(const char *fmt, ...)
__attribute__((format (printf, 1, 2)));
-#ifndef HAVE_STRLCPY_SUPPORT
+/* Matches the libc/libbsd function attribute so we declare this unconditionally: */
extern size_t strlcpy(char *dest, const char *src, size_t size);
-#endif
#endif /* __PERF_CACHE_H */
Index: tip/tools/perf/util/include/linux/compiler.h
===================================================================
--- tip.orig/tools/perf/util/include/linux/compiler.h
+++ tip/tools/perf/util/include/linux/compiler.h
@@ -2,20 +2,29 @@
#define _PERF_LINUX_COMPILER_H_
#ifndef __always_inline
-#define __always_inline inline
+# define __always_inline inline __attribute__((always_inline))
#endif
+
#define __user
+
#ifndef __attribute_const__
-#define __attribute_const__
+# define __attribute_const__
#endif
#ifndef __maybe_unused
-#define __maybe_unused __attribute__((unused))
+# define __maybe_unused __attribute__((unused))
+#endif
+
+#ifndef __packed
+# define __packed __attribute__((__packed__))
#endif
-#define __packed __attribute__((__packed__))
#ifndef __force
-#define __force
+# define __force
+#endif
+
+#ifndef __weak
+# define __weak __attribute__((weak))
#endif
#endif
Index: tip/tools/perf/util/path.c
===================================================================
--- tip.orig/tools/perf/util/path.c
+++ tip/tools/perf/util/path.c
@@ -22,19 +22,23 @@ static const char *get_perf_dir(void)
return ".";
}
-#ifndef HAVE_STRLCPY_SUPPORT
-size_t strlcpy(char *dest, const char *src, size_t size)
+/*
+ * If libc has strlcpy() then that version will override this
+ * implementation:
+ */
+size_t __weak strlcpy(char *dest, const char *src, size_t size)
{
size_t ret = strlen(src);
if (size) {
size_t len = (ret >= size) ? size - 1 : ret;
+
memcpy(dest, src, len);
dest[len] = '\0';
}
+
return ret;
}
-#endif
static char *get_pathname(void)
{
--
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