Re: ask for your help about a patch (commit: 9845cbb)

["gux.fnst" <gux.fnst@cn.fujitsu.com>]

On 04/14/2014 06:37 PM, Kirill A. Shutemov wrote:
> gux.fnst wrote:
>> Hi Kirill,
> Hi Xing,
>
> Please always CC to mailing list for upstream-related questions.
> I've added linux-mm@ to CC.

OK, got it.

> VM_FAULT_FALLBACK is
> fallback required.
> ---------------------------------------------------------------------------------------------------------------------------
>
> It is a little difficult to reproduce this problem fixed by this patch
> for me. Could you give me some
> hint about how to do this - “allocate a huge page to replace zero page
> but hit the memcg limit"?
> I used this script:
>
> #!/bin/sh -efu
>
> set -efux
>
> mount -t cgroup none /sys/fs/cgroup
> mkdir /sys/fs/cgroup/test
> echo "10M" > /sys/fs/cgroup/test/memory.limit_in_bytes
> echo "10M" > /sys/fs/cgroup/test/memory.memsw.limit_in_bytes
>
> echo $$ > /sys/fs/cgroup/test/tasks
> /host/home/kas/var/mmaptest_zero
> echo ok
>
> Where /host/home/kas/var/mmaptest_zero is:
>
> #include <assert.h>
> #include <fcntl.h>
> #include <stdio.h>
> #include <stdlib.h>
> #include <unistd.h>
> #include <sys/types.h>
> #include <sys/mman.h>
>
> #define MB (1024 * 1024)
> #define SIZE (256 * MB)
>
> int main(int argc, char **argv)
> {
> 	int i;
> 	char *p;
>
> 	posix_memalign((void **)&p, 2 * MB, SIZE);
> 	printf("p: %p\n", p);
> 	fork();
> 	for (i = 0; i < SIZE; i += 4096)
> 		assert(p[i] == 0);
>
> 	for (i = 0; i < SIZE; i += 4096)
> 		p[i] = 1;
>
> 	pause();
> 	return 0;
> }
>
> Without the patch it hangs, but should trigger OOM.
>

Thank you very much.

Regards,
Xing Gu

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