Hi Tejun,
On Thu, May 15, 2014 at 12:55:17AM -0400, Tejun Heo wrote:
> Hello,
>
> On Thu, May 15, 2014 at 12:50:39PM +0800, Jet Chen wrote:
> > FYI, we noticed the below changes on
> >
> > git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup.git
> > review-kill-tree_mutex
> > commit a0f9ec1f181534694cb5bf40b7b56515b8cabef9 ("cgroup: use
> > cgroup_kn_lock_live() in other cgroup kernfs methods")
> >
> > Test case : lkp-nex05/will-it-scale/writeseek
> >
> > 2074b6e38668e62 a0f9ec1f181534694cb5bf40b
> > --------------- -------------------------
2074b6e38668e62 is the base of comparison. So "-4.3%
will-it-scale.per_thread_ops"
in the below line means a0f9ec1f18 has lower will-it-scale throughput.
> > 1027273 ~ 0% -4.3% 982732 ~ 0% TOTAL
> > will-it-scale.per_thread_ops
> > 136 ~ 3% -43.1% 77 ~43% TOTAL proc-vmstat.nr_dirtied
> > 0.51 ~ 3% +98.0% 1.01 ~ 4% TOTAL
> > perf-profile.cpu-cycles.shmem_write_end.generic_perform_write.__generic_file_aio_write.generic_file_aio_write.do_sync_write
> > 1078 ~ 9% -16.3% 903 ~11% TOTAL
> > numa-meminfo.node0.Unevictable
> > 269 ~ 9% -16.2% 225 ~11% TOTAL
> > numa-vmstat.node0.nr_unevictable
> > 1.64 ~ 1% -14.3% 1.41 ~ 4% TOTAL
> > perf-profile.cpu-cycles.find_lock_entry.shmem_getpage_gfp.shmem_write_begin.generic_perform_write.__generic_file_aio_write
> > 1.62 ~ 2% +14.1% 1.84 ~ 1% TOTAL
> > perf-profile.cpu-cycles.lseek64
The perf-profile.cpu-cycles.* lines are from "perf record/report".
The last line shows that lseek64() takes 1.62% CPU cycles for
commit 2074b6e38668e62 and that percent increased by +14.1% on
a0f9ec1f181. One of the raw perf record output is
1.84% writeseek_proce libc-2.17.so [.] lseek64
|
--- lseek64
There are 5 runs and 1.62% is the average value.
> I have no idea how to read the above. Which direction is plus and
> which is minus? Are they counting cpu cycles? Which files is the
> test seeking?
It's tmpfs files. Because the will-it-scale test case is mean to
measure scalability of syscalls. We do not use HDD/SSD etc. storage
devices when running it.
The will-it-scale/writeseek test code is
char *testcase_description = "Separate file seek+write";
void testcase(unsigned long long *iterations)
{
char buf[BUFLEN];
char tmpfile[] = "/tmp/willitscale.XXXXXX";
int fd = mkstemp(tmpfile);
memset(buf, 0, sizeof(buf));
assert(fd >= 0);
unlink(tmpfile);
while (1) {
lseek(fd, 0, SEEK_SET);
assert(write(fd, buf, BUFLEN) == BUFLEN);
(*iterations)++;
}
}
Thanks,
Fengguang
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