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From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>, bpf@vger.kernel.org,
	daniel@iogearbox.net, andrii@kernel.org, martin.lau@kernel.org,
	akpm@linux-foundation.org, peterz@infradead.org, vbabka@suse.cz,
	rostedt@goodmis.org, shakeel.butt@linux.dev, mhocko@suse.com,
	linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH mm] mm/page_alloc: Avoid second trylock of zone->lock
Message-ID: <20250331081143.cPXjY7PZ@linutronix.de>
References: <20250331002809.94758-1-alexei.starovoitov@gmail.com>
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In-Reply-To: <20250331002809.94758-1-alexei.starovoitov@gmail.com>

On 2025-03-30 17:28:09 [-0700], Alexei Starovoitov wrote:
> From: Alexei Starovoitov <ast@kernel.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@linux-foundation.org>
> Fixes: 97769a53f117 ("mm, bpf: Introduce try_alloc_pages() for opportunistic page allocation")
> Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Reviewed-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

Sebastian