From: Shakeel Butt <shakeel.butt@linux.dev>
To: Kuniyuki Iwashima <kuniyu@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Johannes Weiner <hannes@cmpxchg.org>,
Michal Hocko <mhocko@kernel.org>,
Roman Gushchin <roman.gushchin@linux.dev>,
Muchun Song <muchun.song@linux.dev>,
Kuniyuki Iwashima <kuni1840@gmail.com>,
linux-mm@kvack.org, cgroups@vger.kernel.org
Subject: Re: [PATCH v2 3/6] memcg: Annotate slow paths in consume_stock() and refill_stock().
Date: Wed, 28 Oct 2026 17:55:31 -0700 [thread overview]
Message-ID: <auKZIA-0j9WT_gFU@linux.dev> (raw)
In-Reply-To: <20261028185034.3607746-4-kuniyu@google.com>
On Wed, Oct 28, 2026 at 06:50:15PM +0000, Kuniyuki Iwashima wrote:
> In consume_stock() and refill_stock(), each per-CPU stock slot
> holds up to MEMCG_STOCK_HIGH (64) pages, so depleting a slot in
> consume_stock() (!stock_pages) or trimming a slot in refill_stock()
> (stock_pages > MEMCG_STOCK_HIGH) happens at most once per batch.
>
> Similarly, requests larger than MEMCG_CHARGE_BATCH, local_trylock()
> failure, and insufficient cached pages (stock_pages < nr_pages)
> are all slow paths.
>
> Without unlikely() annotations (when building without FDO, or
> when an FDO profile does not cover a caller), the compiler treats
> these branches as likely and inlines css_put() in consume_stock()
> and memcg_uncharge() in refill_stock() right into the middle of
> the hot path.
Please state the compiler along with its version here. I didn't see this behavior
on gcc 14.
next prev parent reply other threads:[~2026-10-29 0:55 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-10-28 18:50 [PATCH v2 0/6] memcg: Batch mod_memcg_state() for MEMCG_SOCK Kuniyuki Iwashima
2026-10-28 18:50 ` [PATCH v2 1/6] memcg: Remove unnecessary READ_ONCE() under memcg_stock.lock Kuniyuki Iwashima
2026-10-29 0:48 ` Shakeel Butt
2026-10-29 1:44 ` Kuniyuki Iwashima
2026-10-28 18:50 ` [PATCH v2 2/6] memcg: Reduce nesting in consume_stock() and refill_stock() Kuniyuki Iwashima
2026-10-29 0:50 ` Shakeel Butt
2026-10-28 18:50 ` [PATCH v2 3/6] memcg: Annotate slow paths " Kuniyuki Iwashima
2026-10-29 0:55 ` Shakeel Butt [this message]
2026-10-29 1:49 ` Kuniyuki Iwashima
2026-10-28 18:50 ` [PATCH v2 4/6] memcg: Batch mod_memcg_state() for MEMCG_SOCK Kuniyuki Iwashima
2026-10-28 18:50 ` [PATCH v2 5/6] memcg: Uncharge pages outside memcg_stock.lock in __refill_stock() Kuniyuki Iwashima
2026-10-28 18:50 ` [PATCH v2 6/6] selftests: cgroup: Deflake test_memcg_sock() in test_memcontrol.c Kuniyuki Iwashima
2026-10-29 0:41 ` [PATCH v2 0/6] memcg: Batch mod_memcg_state() for MEMCG_SOCK Shakeel Butt
2026-10-29 0:52 ` Shakeel Butt
2026-10-29 1:35 ` Kuniyuki Iwashima
2026-10-29 2:32 ` Kuniyuki Iwashima
2026-10-29 20:02 ` Shakeel Butt
2026-10-29 20:26 ` Kuniyuki Iwashima
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