With turning on cache feature of libunwind, stack tracing
becomes two times faster(in my small test).
Target program:
#include <unistd.h>
#include <sys/types.h>
#define N 0xfff
int
main(void)
{
uid_t uid;
int i;
for (i = 0; i < N; i++)
getuid();
return 0;
}
With enabling cache of libunwind:
% /usr/bin/time ./strace -o /dev/null -e'getuid' -k ./a.out
0.61user 1.33system 0:01.97elapsed 98%CPU (0avgtext+0avgdata
1376maxresident)k
0inputs+0outputs (0major+590269minor)pagefaults 0swaps
Without enabling cache of libunwind:
% /usr/bin/time ./strace -o /dev/null -e'getuid' -k ./a.out
0.80user 2.61system 0:03.46elapsed 98%CPU (0avgtext+0avgdata
1372maxresident)k
0inputs+0outputs (0major+639381minor)pagefaults 0swaps
Signed-off-by: Masatake YAMATO <[email protected]>
---
unwind.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/unwind.c b/unwind.c
index 4cb6325..ed2d141 100644
--- a/unwind.c
+++ b/unwind.c
@@ -80,6 +80,7 @@ init_unwind_addr_space(void)
libunwind_as = unw_create_addr_space(&_UPT_accessors, 0);
if (!libunwind_as)
error_msg_and_die("failed to create address space for stack
tracing");
+ unw_set_caching_policy(libunwind_as, UNW_CACHE_GLOBAL);
}
static void
@@ -135,6 +136,8 @@ build_mmap_cache(struct tcb *tcp)
struct mmap_cache_t *cache_head;
FILE *fp;
+ unw_flush_cache (libunwind_as, 0, 0);
+
sprintf(filename, "/proc/%d/maps", tcp->pid);
fp = fopen(filename, "r");
if (!fp) {
--
1.8.3.1
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