I guess it is enough to show some examples:
[root@doppio linux-2.6-tip]# rm -f perf.data*
[root@doppio linux-2.6-tip]# ls -la perf.data*
ls: cannot access perf.data*: No such file or directory
[root@doppio linux-2.6-tip]# perf record -f find / > /dev/null
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.062 MB perf.data (~2699 samples) ]
[root@doppio linux-2.6-tip]# ls -la perf.data*
-rw------- 1 root root 74440 2009-12-14 20:03 perf.data
[root@doppio linux-2.6-tip]# perf record -f find / > /dev/null
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.062 MB perf.data (~2692 samples) ]
[root@doppio linux-2.6-tip]# ls -la perf.data*
-rw------- 1 root root 74280 2009-12-14 20:03 perf.data
-rw------- 1 root root 74440 2009-12-14 20:03 perf.data.old
[root@doppio linux-2.6-tip]# perf diff | head -5
1 -34994580 /lib64/libc-2.10.1.so _IO_vfprintf_internal
2 -15307806 [kernel.kallsyms] __kmalloc
3 +1 +3665941 /lib64/libc-2.10.1.so __GI_memmove
4 +4 +23508995 /lib64/libc-2.10.1.so _int_malloc
5 +7 +38538813 [kernel.kallsyms] __d_lookup
[root@doppio linux-2.6-tip]# perf diff -p | head -5
1 +1.00% /lib64/libc-2.10.1.so _IO_vfprintf_internal
2 [kernel.kallsyms] __kmalloc
3 +1 /lib64/libc-2.10.1.so __GI_memmove
4 +4 /lib64/libc-2.10.1.so _int_malloc
5 +7 -1.00% [kernel.kallsyms] __d_lookup
[root@doppio linux-2.6-tip]# perf diff -v | head -5
1 361449551 326454971 -34994580 /lib64/libc-2.10.1.so _IO_vfprintf_internal
2 151009241 135701435 -15307806 [kernel.kallsyms] __kmalloc
3 +1 101805328 105471269 +3665941 /lib64/libc-2.10.1.so __GI_memmove
4 +4 78041440 101550435 +23508995 /lib64/libc-2.10.1.so _int_malloc
5 +7 59536172 98074985 +38538813 [kernel.kallsyms] __d_lookup
[root@doppio linux-2.6-tip]# perf diff -vp | head -5
1 9.00% 8.00% +1.00% /lib64/libc-2.10.1.so _IO_vfprintf_internal
2 3.00% 3.00% [kernel.kallsyms] __kmalloc
3 +1 2.00% 2.00% /lib64/libc-2.10.1.so __GI_memmove
4 +4 2.00% 2.00% /lib64/libc-2.10.1.so _int_malloc
5 +7 1.00% 2.00% -1.00% [kernel.kallsyms] __d_lookup
[root@doppio linux-2.6-tip]#
This should be enough for diffs where the system is non
volatile, i.e. when one doesn't updates binaries.
For volatile environments, stay tuned for the next perf tool
feature: a buildid cache populated by 'perf record', managed by
'perf buildid-cache' a-la ccache, and used by all the report
tools.
Signed-off-by: Arnaldo Carvalho de Melo
Cc: "Paul E. McKenney"
Cc: Stephen Hemminger
Cc: Frédéric Weisbecker
Cc: Mike Galbraith
Cc: Peter Zijlstra
Cc: Paul Mackerras
Cc: Paul E. McKenney
LKML-Reference:
Signed-off-by: Ingo Molnar
