From: Waiman Long <longman@redhat.com>
To: Johannes Weiner <hannes@cmpxchg.org>,
Michal Hocko <mhocko@kernel.org>,
Vladimir Davydov <vdavydov.dev@gmail.com>,
Andrew Morton <akpm@linux-foundation.org>,
Tejun Heo <tj@kernel.org>, Christoph Lameter <cl@linux.com>,
Pekka Enberg <penberg@kernel.org>,
David Rientjes <rientjes@google.com>,
Joonsoo Kim <iamjoonsoo.kim@lge.com>,
Vlastimil Babka <vbabka@suse.cz>, Roman Gushchin <guro@fb.com>
Cc: linux-kernel@vger.kernel.org, cgroups@vger.kernel.org,
linux-mm@kvack.org, Shakeel Butt <shakeelb@google.com>,
Muchun Song <songmuchun@bytedance.com>,
Alex Shi <alex.shi@linux.alibaba.com>,
Chris Down <chris@chrisdown.name>,
Yafang Shao <laoar.shao@gmail.com>,
Wei Yang <richard.weiyang@gmail.com>,
Masayoshi Mizuma <msys.mizuma@gmail.com>,
Xing Zhengjun <zhengjun.xing@linux.intel.com>,
Matthew Wilcox <willy@infradead.org>,
Waiman Long <longman@redhat.com>
Subject: [PATCH-next v5 3/4] mm/memcg: Improve refill_obj_stock() performance
Date: Tue, 20 Apr 2021 15:29:06 -0400 [thread overview]
Message-ID: <20210420192907.30880-4-longman@redhat.com> (raw)
In-Reply-To: <20210420192907.30880-1-longman@redhat.com>
There are two issues with the current refill_obj_stock() code. First of
all, when nr_bytes reaches over PAGE_SIZE, it calls drain_obj_stock() to
atomically flush out remaining bytes to obj_cgroup, clear cached_objcg
and do a obj_cgroup_put(). It is likely that the same obj_cgroup will
be used again which leads to another call to drain_obj_stock() and
obj_cgroup_get() as well as atomically retrieve the available byte from
obj_cgroup. That is costly. Instead, we should just uncharge the excess
pages, reduce the stock bytes and be done with it. The drain_obj_stock()
function should only be called when obj_cgroup changes.
Secondly, when charging an object of size not less than a page in
obj_cgroup_charge(), it is possible that the remaining bytes to be
refilled to the stock will overflow a page and cause refill_obj_stock()
to uncharge 1 page. To avoid the additional uncharge in this case,
a new overfill flag is added to refill_obj_stock() which will be set
when called from obj_cgroup_charge().
A multithreaded kmalloc+kfree microbenchmark on a 2-socket 48-core
96-thread x86-64 system with 96 testing threads were run. Before this
patch, the total number of kilo kmalloc+kfree operations done for a 4k
large object by all the testing threads per second were 4,304 kops/s
(cgroup v1) and 8,478 kops/s (cgroup v2). After applying this patch, the
number were 4,731 (cgroup v1) and 418,142 (cgroup v2) respectively. This
represents a performance improvement of 1.10X (cgroup v1) and 49.3X
(cgroup v2).
Signed-off-by: Waiman Long <longman@redhat.com>
---
mm/memcontrol.c | 20 ++++++++++++++------
1 file changed, 14 insertions(+), 6 deletions(-)
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 292b4783b1a7..2f87d0b05092 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -3153,10 +3153,12 @@ static bool obj_stock_flush_required(struct memcg_stock_pcp *stock,
return false;
}
-static void refill_obj_stock(struct obj_cgroup *objcg, unsigned int nr_bytes)
+static void refill_obj_stock(struct obj_cgroup *objcg, unsigned int nr_bytes,
+ bool overfill)
{
struct memcg_stock_pcp *stock;
unsigned long flags;
+ unsigned int nr_pages = 0;
local_irq_save(flags);
@@ -3165,14 +3167,20 @@ static void refill_obj_stock(struct obj_cgroup *objcg, unsigned int nr_bytes)
drain_obj_stock(stock);
obj_cgroup_get(objcg);
stock->cached_objcg = objcg;
- stock->nr_bytes = atomic_xchg(&objcg->nr_charged_bytes, 0);
+ stock->nr_bytes = atomic_read(&objcg->nr_charged_bytes)
+ ? atomic_xchg(&objcg->nr_charged_bytes, 0) : 0;
}
stock->nr_bytes += nr_bytes;
- if (stock->nr_bytes > PAGE_SIZE)
- drain_obj_stock(stock);
+ if (!overfill && (stock->nr_bytes > PAGE_SIZE)) {
+ nr_pages = stock->nr_bytes >> PAGE_SHIFT;
+ stock->nr_bytes &= (PAGE_SIZE - 1);
+ }
local_irq_restore(flags);
+
+ if (nr_pages)
+ obj_cgroup_uncharge_pages(objcg, nr_pages);
}
int obj_cgroup_charge(struct obj_cgroup *objcg, gfp_t gfp, size_t size)
@@ -3201,14 +3209,14 @@ int obj_cgroup_charge(struct obj_cgroup *objcg, gfp_t gfp, size_t size)
ret = obj_cgroup_charge_pages(objcg, gfp, nr_pages);
if (!ret && nr_bytes)
- refill_obj_stock(objcg, PAGE_SIZE - nr_bytes);
+ refill_obj_stock(objcg, PAGE_SIZE - nr_bytes, true);
return ret;
}
void obj_cgroup_uncharge(struct obj_cgroup *objcg, size_t size)
{
- refill_obj_stock(objcg, size);
+ refill_obj_stock(objcg, size, false);
}
#endif /* CONFIG_MEMCG_KMEM */
--
2.18.1
next prev parent reply other threads:[~2021-04-20 19:30 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-20 19:29 [PATCH-next v5 0/4] mm/memcg: Reduce kmemcache memory accounting overhead Waiman Long
2021-04-20 19:29 ` [PATCH-next v5 1/4] mm/memcg: Move mod_objcg_state() to memcontrol.c Waiman Long
2021-04-21 15:26 ` Shakeel Butt
2021-04-21 23:08 ` Roman Gushchin
2021-04-20 19:29 ` [PATCH-next v5 2/4] mm/memcg: Cache vmstat data in percpu memcg_stock_pcp Waiman Long
2021-04-21 23:28 ` Roman Gushchin
2021-04-22 16:58 ` Waiman Long
2021-04-23 1:56 ` Roman Gushchin
2021-04-23 16:52 ` Waiman Long
2021-04-20 19:29 ` Waiman Long [this message]
2021-04-21 23:55 ` [PATCH-next v5 3/4] mm/memcg: Improve refill_obj_stock() performance Roman Gushchin
2021-04-22 17:26 ` Waiman Long
2021-04-23 2:28 ` Roman Gushchin
2021-04-23 20:06 ` Waiman Long
2021-04-26 19:24 ` Shakeel Butt
2021-04-20 19:29 ` [PATCH-next v5 4/4] mm/memcg: Optimize user context object stock access Waiman Long
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=20210420192907.30880-4-longman@redhat.com \
--to=longman@redhat.com \
--cc=akpm@linux-foundation.org \
--cc=alex.shi@linux.alibaba.com \
--cc=cgroups@vger.kernel.org \
--cc=chris@chrisdown.name \
--cc=cl@linux.com \
--cc=guro@fb.com \
--cc=hannes@cmpxchg.org \
--cc=iamjoonsoo.kim@lge.com \
--cc=laoar.shao@gmail.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=mhocko@kernel.org \
--cc=msys.mizuma@gmail.com \
--cc=penberg@kernel.org \
--cc=richard.weiyang@gmail.com \
--cc=rientjes@google.com \
--cc=shakeelb@google.com \
--cc=songmuchun@bytedance.com \
--cc=tj@kernel.org \
--cc=vbabka@suse.cz \
--cc=vdavydov.dev@gmail.com \
--cc=willy@infradead.org \
--cc=zhengjun.xing@linux.intel.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).