linux-kernel - Re: [PATCH mm] mm/page_alloc: Avoid second trylock of zone->lock

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Message-ID: <a6z7nozoprpbnf34z2rnah375sgakethpip6rpxtkd6xknqxm3@kxir5he5rbra>
Date: Tue, 1 Apr 2025 21:29:05 -0700
From: Shakeel Butt <shakeel.butt@...ux.dev>
To: Alexei Starovoitov <alexei.starovoitov@...il.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>, bpf@...r.kernel.org, 
	daniel@...earbox.net, andrii@...nel.org, martin.lau@...nel.org, 
	akpm@...ux-foundation.org, peterz@...radead.org, vbabka@...e.cz, bigeasy@...utronix.de, 
	rostedt@...dmis.org, mhocko@...e.com, linux-mm@...ck.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH mm] mm/page_alloc: Avoid second trylock of zone->lock

On Sun, Mar 30, 2025 at 05:28:09PM -0700, Alexei Starovoitov wrote:
> From: Alexei Starovoitov <ast@...nel.org>
> 
> spin_trylock followed by spin_lock will cause extra write cache
> access. If the lock is contended it may cause unnecessary cache
> line bouncing and will execute redundant irq restore/save pair.
> Therefore, check alloc/fpi_flags first and use spin_trylock or
> spin_lock.
> 
> Suggested-by: Linus Torvalds <torvalds@...ux-foundation.org>
> Fixes: 97769a53f117 ("mm, bpf: Introduce try_alloc_pages() for opportunistic page allocation")
> Signed-off-by: Alexei Starovoitov <ast@...nel.org>

Reviewed-by: Shakeel Butt <shakeel.butt@...ux.dev>