From: Pekka Enberg <penberg@gmail.com>
To: Xunlei Pang <xlpang@linux.alibaba.com>
Cc: Christoph Lameter <cl@linux.com>,
Andrew Morton <akpm@linux-foundation.org>,
Wen Yang <wenyang@linux.alibaba.com>,
Yang Shi <yang.shi@linux.alibaba.com>,
Roman Gushchin <guro@fb.com>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 1/2] mm/slub: Introduce two counters for the partial objects
Date: Thu, 2 Jul 2020 14:59:07 +0300 [thread overview]
Message-ID: <CAOJsxLErUqY=eBEaj0G3iRAY-YuyyLnxOnBLTP6SkCjhq1On2g@mail.gmail.com> (raw)
In-Reply-To: <1593678728-128358-1-git-send-email-xlpang@linux.alibaba.com>
On Thu, Jul 2, 2020 at 11:32 AM Xunlei Pang <xlpang@linux.alibaba.com> wrote:
> The node list_lock in count_partial() spend long time iterating
> in case of large amount of partial page lists, which can cause
> thunder herd effect to the list_lock contention, e.g. it cause
> business response-time jitters when accessing "/proc/slabinfo"
> in our production environments.
Would you have any numbers to share to quantify this jitter? I have no
objections to this approach, but I think the original design
deliberately made reading "/proc/slabinfo" more expensive to avoid
atomic operations in the allocation/deallocation paths. It would be
good to understand what is the gain of this approach before we switch
to it. Maybe even run some slab-related benchmark (not sure if there's
something better than hackbench these days) to see if the overhead of
this approach shows up.
> This patch introduces two counters to maintain the actual number
> of partial objects dynamically instead of iterating the partial
> page lists with list_lock held.
>
> New counters of kmem_cache_node are: pfree_objects, ptotal_objects.
> The main operations are under list_lock in slow path, its performance
> impact is minimal.
>
> Co-developed-by: Wen Yang <wenyang@linux.alibaba.com>
> Signed-off-by: Xunlei Pang <xlpang@linux.alibaba.com>
> ---
> mm/slab.h | 2 ++
> mm/slub.c | 38 +++++++++++++++++++++++++++++++++++++-
> 2 files changed, 39 insertions(+), 1 deletion(-)
>
> diff --git a/mm/slab.h b/mm/slab.h
> index 7e94700..5935749 100644
> --- a/mm/slab.h
> +++ b/mm/slab.h
> @@ -616,6 +616,8 @@ struct kmem_cache_node {
> #ifdef CONFIG_SLUB
> unsigned long nr_partial;
> struct list_head partial;
> + atomic_long_t pfree_objects; /* partial free objects */
> + atomic_long_t ptotal_objects; /* partial total objects */
You could rename these to "nr_partial_free_objs" and
"nr_partial_total_objs" for readability.
- Pekka
next prev parent reply other threads:[~2020-07-02 11:59 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-02 8:32 [PATCH 1/2] mm/slub: Introduce two counters for the partial objects Xunlei Pang
2020-07-02 8:32 ` [PATCH 2/2] mm/slub: Get rid of count_partial() Xunlei Pang
2020-07-02 11:59 ` Pekka Enberg [this message]
2020-07-03 9:37 ` [PATCH 1/2] mm/slub: Introduce two counters for the partial objects xunlei
2020-07-07 15:23 ` Pekka Enberg
2020-07-09 14:32 ` Christopher Lameter
2020-07-31 2:57 ` xunlei
2020-07-07 6:59 ` Christopher Lameter
2020-07-31 2:52 ` xunlei
2020-08-06 12:42 ` Vlastimil Babka
2020-08-07 7:25 ` Pekka Enberg
2020-08-07 13:02 ` Christopher Lameter
2020-08-07 17:28 ` Pekka Enberg
2020-08-10 11:56 ` xunlei
2020-08-11 12:52 ` Christopher Lameter
2020-08-20 13:58 ` Pekka Enberg
2020-08-24 9:59 ` xunlei
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='CAOJsxLErUqY=eBEaj0G3iRAY-YuyyLnxOnBLTP6SkCjhq1On2g@mail.gmail.com' \
--to=penberg@gmail.com \
--cc=akpm@linux-foundation.org \
--cc=cl@linux.com \
--cc=guro@fb.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=wenyang@linux.alibaba.com \
--cc=xlpang@linux.alibaba.com \
--cc=yang.shi@linux.alibaba.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).