Re: [clockevents] d5a085970b0: -9.2% will-it-scale.per_thread_ops

[Fengguang Wu <fengguang.wu@intel.com>]

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On Thu, Jun 26, 2014 at 09:35:11AM +0530, Viresh Kumar wrote:
> On 26 June 2014 07:16, Fengguang Wu <fengguang.wu@intel.com> wrote:
> > I'm not sure how the simple commit will impact will-it-scale/pwrite2
> > throughput. Just in case you can see more clues.
> >
> > git://git.linaro.org/people/vireshk/linux tick/ONESHOT-STOPPED
> > commit d5a085970b0b88b8c82303d2c45f09c9427fd02a ("clockevents: x86: add support for ONESHOT_STOPPED mode")
> >
> > test case: nhm4/will-it-scale/pwrite2
> 
> What is this test all about ?

It calls the pwrite2() syscall in parallel, on one single tmpfs file.

https://github.com/antonblanchard/will-it-scale.git

Thanks,
Fengguang

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#define _XOPEN_SOURCE 500
#include <fcntl.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <assert.h>

#define BUFLEN 4096

static char tmpfile[] = "/tmp/willitscale.XXXXXX";

char *testcase_description = "Same file pwrite";

void testcase_prepare(void)
{
	char buf[BUFLEN];
	int fd = mkstemp(tmpfile);

	memset(buf, 0, sizeof(buf));
	assert(fd >= 0);
	assert(write(fd, buf, sizeof(buf)) == sizeof(buf));
	close(fd);
}

void testcase(unsigned long long *iterations)
{
	char buf[BUFLEN];
	int fd = open(tmpfile, O_RDWR);

	assert(fd >= 0);

	while (1) {
		assert(pwrite(fd, buf, BUFLEN, 0) == BUFLEN);

		(*iterations)++;
	}
}

void testcase_cleanup(void)
{
	unlink(tmpfile);
}