From: Tim Chen <tim.c.chen@linux.intel.com>
To: Johannes Weiner <hannes@cmpxchg.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Michal Hocko <mhocko@suse.cz>,
Vladimir Davydov <vdavydov.dev@gmail.com>,
Dave Hansen <dave.hansen@intel.com>,
Ying Huang <ying.huang@intel.com>,
linux-mm@kvack.org, cgroups@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 3/3] mm: Fix missing mem cgroup soft limit tree updates
Date: Mon, 22 Feb 2021 10:38:27 -0800 [thread overview]
Message-ID: <d141f9ec-5502-b011-167f-e24d891b0dfe@linux.intel.com> (raw)
In-Reply-To: <YC4BcsNFEmW7XeqB@cmpxchg.org>
On 2/17/21 9:56 PM, Johannes Weiner wrote:
>> static inline void uncharge_gather_clear(struct uncharge_gather *ug)
>> @@ -6849,7 +6850,13 @@ static void uncharge_page(struct page *page, struct uncharge_gather *ug)
>> * exclusive access to the page.
>> */
>>
>> - if (ug->memcg != page_memcg(page)) {
>> + if (ug->memcg != page_memcg(page) ||
>> + /*
>> + * Update soft limit tree used in v1 cgroup in page batch for
>> + * the same node. Relevant only to v1 cgroup with a soft limit.
>> + */
>> + (ug->dummy_page && ug->nid != page_to_nid(page) &&
>> + ug->memcg->soft_limit != PAGE_COUNTER_MAX)) {
>
> Sorry, I used weird phrasing in my last email.
>
> Can you please preface the checks you're adding with a
> !cgroup_subsys_on_dfl(memory_cgrp_subsys) to static branch for
> cgroup1? The uncharge path is pretty hot, and this would avoid the
> runtime overhead on cgroup2 at least, which doesn't have the SL.
>
> Also, do we need the ug->dummy_page check? It's only NULL on the first
> loop - where ug->memcg is NULL as well and the branch is taken anyway.
>
> The soft limit check is also slightly cheaper than the nid check, as
> page_to_nid() might be out-of-line, so we should do it first. This?
>
> /*
> * Batch-uncharge all pages of the same memcg.
> *
> * Unless we're looking at a cgroup1 with a softlimit
> * set: the soft limit trees are maintained per-node
> * and updated on uncharge (via dummy_page), so keep
> * batches confined to a single node as well.
> */
> if (ug->memcg != page_memcg(page) ||
> (!cgroup_subsys_on_dfl(memory_cgrp_subsys) &&
> ug->memcg->soft_limit != PAGE_COUNTER_MAX &&
> ug->nid != page_to_nid(page)))
>
Johannes,
Thanks for your feedback. Since Michal has concerns about the overhead
this patch could incur, I think we'll hold the patch for now. If later
on Michal think that this patch is a good idea, I'll incorporate these
changes you suggested.
Tim
next prev parent reply other threads:[~2021-02-22 18:40 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-17 20:41 [PATCH v2 0/3] Soft limit memory management bug fixes Tim Chen
2021-02-17 20:41 ` [PATCH v2 1/3] mm: Fix dropped memcg from mem cgroup soft limit tree Tim Chen
2021-02-18 8:24 ` Michal Hocko
2021-02-18 18:30 ` Tim Chen
2021-02-18 19:13 ` Michal Hocko
2021-02-18 19:51 ` Tim Chen
2021-02-18 19:13 ` Michal Hocko
2021-03-04 17:35 ` Tim Chen
2021-03-05 9:11 ` Michal Hocko
2021-03-05 19:07 ` Tim Chen
2021-03-08 8:34 ` Michal Hocko
2021-02-17 20:41 ` [PATCH v2 2/3] mm: Force update of mem cgroup soft limit tree on usage excess Tim Chen
2021-02-19 9:11 ` Michal Hocko
2021-02-19 18:59 ` Tim Chen
2021-02-20 16:23 ` Tim Chen
2021-02-22 8:40 ` Michal Hocko
2021-02-22 17:41 ` Tim Chen
2021-02-22 19:09 ` Michal Hocko
2021-02-22 19:23 ` Tim Chen
2021-02-22 19:48 ` Tim Chen
2021-02-24 11:53 ` Michal Hocko
2021-02-25 22:48 ` Tim Chen
2021-02-26 8:52 ` Michal Hocko
2021-02-27 0:56 ` Tim Chen
2021-03-01 7:39 ` Michal Hocko
2021-02-25 22:25 ` Tim Chen
2021-03-02 6:25 ` [mm] 4f09feb8bf: vm-scalability.throughput -4.3% regression kernel test robot
2021-02-17 20:41 ` [PATCH v2 3/3] mm: Fix missing mem cgroup soft limit tree updates Tim Chen
2021-02-18 5:56 ` Johannes Weiner
2021-02-22 18:38 ` Tim Chen [this message]
2021-02-23 15:18 ` Johannes Weiner
2021-02-19 9:16 ` Michal Hocko
2021-02-19 19:28 ` Tim Chen
2021-02-22 8:41 ` Michal Hocko
2021-02-22 17:45 ` Tim Chen
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