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Wed, 02 Apr 2025 16:30:18 +0800 From: "Huang, Ying" To: Songtang Liu Cc: akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, zhengqi.arch@bytedance.com, songmuchun@bytedance.com Subject: Re: [PATCH] mm: page_alloc: Remove redundant READ_ONCE In-Reply-To: (Songtang Liu's message of "Wed, 2 Apr 2025 03:41:16 -0400") References: Date: Wed, 02 Apr 2025 16:30:19 +0800 Message-ID: <87wmc3ufs4.fsf@DESKTOP-5N7EMDA> User-Agent: Gnus/5.13 (Gnus v5.13) MIME-Version: 1.0 Content-Type: text/plain; charset=ascii X-Rspamd-Queue-Id: 7548DA0006 X-Stat-Signature: pdzm1iqb86dtjom84pzwmsk8uzf8tapx X-Rspam-User: X-Rspamd-Server: rspam12 X-HE-Tag: 1743582622-757527 X-HE-Meta: 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 KrYsbT3K o9YtGh7sqmT4u2dlc30U2M/pbwAEm/Eg3I2HDQaqDeZUTbW1FhSRQU+XK4C1p7ByxoT14bufrf4FRMz268w6xIVACHsxYOdE8JsU9tJe9m/HXKcq04zi0X8Tcl0g98ojflapDDarsGFUrxiQDVMZ/eF2yRmK/HBeqMZ4/BTuVQc0lxPGh7ql6yxj1rdbin7YTbL4pPtYNVoJGMmlrgujNgm+4U4odPN+TAwvVVptKgkm4HOx3YfdQfatuYEbUdZM4stftQQ94nWnsNkOPc/xbIvT+aJ+aLjAHX5MYwKzTgAp5ZVo= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000006, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Songtang Liu writes: > In the current code, batch is a local variable, and it cannot be > concurrently modified. It's unnecessary to use READ_ONCE here, > so remove it. > > Fixes: 51a755c56dc0 ("mm: tune PCP high automatically") > Signed-off-by: Songtang Liu > --- > mm/page_alloc.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index e3ea5bf5c459..6edc6e57d4f8 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -2661,7 +2661,7 @@ static void free_frozen_page_commit(struct zone *zone, > free_high = (pcp->free_count >= batch && > (pcp->flags & PCPF_PREV_FREE_HIGH_ORDER) && > (!(pcp->flags & PCPF_FREE_HIGH_BATCH) || > - pcp->count >= READ_ONCE(batch))); > + pcp->count >= batch)); Nice catch! Reviewed-by: Huang Ying > pcp->flags |= PCPF_PREV_FREE_HIGH_ORDER; > } else if (pcp->flags & PCPF_PREV_FREE_HIGH_ORDER) { > pcp->flags &= ~PCPF_PREV_FREE_HIGH_ORDER; --- Best Regards, Huang, Ying