From: Andrew Morton <akpm@linux-foundation.org>
To: Xishi Qiu <qiuxishi@huawei.com>
Cc: Vlastimil Babka <vbabka@suse.cz>,
Mel Gorman <mgorman@techsingularity.net>,
Michal Hocko <mhocko@suse.com>,
Johannes Weiner <hannes@cmpxchg.org>,
Joonsoo Kim <iamjoonsoo.kim@lge.com>,
"'Kirill A . Shutemov'" <kirill.shutemov@linux.intel.com>,
Taku Izumi <izumi.taku@jp.fujitsu.com>,
Yisheng Xie <xieyisheng1@huawei.com>,
Linux MM <linux-mm@kvack.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [RFC][PATCH] mm: merge as soon as possible when pcp alloc/free
Date: Mon, 7 Nov 2016 15:45:32 -0800 [thread overview]
Message-ID: <20161107154532.e3573bc08324e24aad6d1e26@linux-foundation.org> (raw)
In-Reply-To: <581D9103.1000202@huawei.com>
On Sat, 5 Nov 2016 15:57:55 +0800 Xishi Qiu <qiuxishi@huawei.com> wrote:
> Usually the memory of android phones is very small, so after a long
> running, the fragment is very large. Kernel stack which called by
> alloc_thread_stack_node() usually alloc 16K memory, and it failed
> frequently.
>
> However we have CONFIG_VMAP_STACK now, but it do not support arm64,
> and maybe it has some regression because of vmalloc, it need to
> find an area and create page table dynamically, this will take a short
> time.
>
> I think we can merge as soon as possible when pcp alloc/free to reduce
> fragment. The pcp page is hot page, so free it will cause cache miss,
> I use perf to test it, but it seems the regression is not so much, maybe
> it need to test more. Any reply is welcome.
per-cpu pages may not be worth the effort on such systems - probably
benefit is small. I discussed this with Mel a few years ago and I
think he did some testing, but I forget the results?
Anyway, if per-cpu pages are causing problems then perhaps we should
have a Kconfig option which simply eliminates them: free these pages
direct into the buddy. If the resulting code is clean-looking and the
performance testing on small systems shows decent results then that
should address the issues you're seeing.
next prev parent reply other threads:[~2016-11-07 23:45 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-11-05 7:57 [RFC][PATCH] mm: merge as soon as possible when pcp alloc/free Xishi Qiu
2016-11-05 12:29 ` Anshuman Khandual
2016-11-07 1:48 ` Xishi Qiu
2016-11-07 4:50 ` Anshuman Khandual
2016-11-07 23:45 ` Andrew Morton [this message]
2016-11-08 11:03 ` Mel Gorman
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20161107154532.e3573bc08324e24aad6d1e26@linux-foundation.org \
--to=akpm@linux-foundation.org \
--cc=hannes@cmpxchg.org \
--cc=iamjoonsoo.kim@lge.com \
--cc=izumi.taku@jp.fujitsu.com \
--cc=kirill.shutemov@linux.intel.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=mgorman@techsingularity.net \
--cc=mhocko@suse.com \
--cc=qiuxishi@huawei.com \
--cc=vbabka@suse.cz \
--cc=xieyisheng1@huawei.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).