Hi Zheng,
On 04/23/2013 09:49 PM, Zheng Liu wrote:
Hi Konstantin,
On Tue, Apr 23, 2013 at 05:02:34PM +0400, Konstantin Khlebnikov wrote:
Zheng Liu wrote:
Hi all,
Recently we meet a performance regression about mmaped page. When we upgrade
our product system from 2.6.18 kernel to a latest kernel, such as 2.6.32 kernel,
we will find that mmaped pages are reclaimed very quickly. We found that when
we hit a minor fault mark_page_accessed() is called in 2.6.18 kernel, but in
2.6.32 kernel we don't call mark_page_accesed(). This means that mmaped pages
in 2.6.18 kernel are activated and moved into active list. While in 2.6.32
kernel mmaped pages are still kept in inactive list.
So my question is why we call mark_page_accessed() in 2.6.18 kernel, but don't
call it in 2.6.32 kernel. Has any reason here?
Behavior was changed in commit
v2.6.28-6130-gbf3f3bc "mm: don't mark_page_accessed in fault path"
Thanks for pointing it out.
Please see also commits
v3.2-4876-g34dbc67 "vmscan: promote shared file mapped pages" and
Yes, I will give it try. If I understand correctly, this commit is
useful for multi-processes program that access a shared mmaped page,
but that could not be useful for us because our program is multi-thread.
What's the difference behavior between multi-processes and multi-thread
in this case?
v3.2-4877-gc909e99 "vmscan: activate executable pages after first usage".
We have backported this patch, but it is useless. This commit only
tries to activate a executable page, but our mmaped pages aren't with
this flag.
Additional question is that currently mmaped page is reclaimed too
quickly. I think maybe we need to adjust our page reclaim strategy to
balance number of pages between mmaped page and file page cache. Now
every time we access a page using read(2)/write(2), this page will be
touched. But after first time we touch a mmaped page, we never touch it
again except that this page is evicted.
Regards,
- Zheng
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