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Fri, 13 Feb 2026 12:09:06 -0800 (PST) Received: from localhost ([2603:7000:c00:3a00:365a:60ff:fe62:ff29]) by smtp.gmail.com with ESMTPSA id af79cd13be357-8cb2b1c7ef7sm723625085a.28.2026.02.13.12.09.05 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 13 Feb 2026 12:09:05 -0800 (PST) Date: Fri, 13 Feb 2026 15:08:57 -0500 From: Johannes Weiner To: Kairui Song Cc: cgroups@vger.kernel.org, linux-mm@kvack.org, Michal Hocko , Roman Gushchin , Shakeel Butt , Muchun Song , Andrew Morton , linux-kernel@vger.kernel.org, Kairui Song Subject: Re: [PATCH] memcg: consolidate private id refcount get/put helpers Message-ID: References: <20260213-memcg-privid-v1-1-d8cb7afcf831@tencent.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260213-memcg-privid-v1-1-d8cb7afcf831@tencent.com> X-Stat-Signature: dddnru9jmxabpdzj5uffx13g53zrac9u X-Rspamd-Queue-Id: 563091C0013 X-Rspam-User: X-Rspamd-Server: rspam04 X-HE-Tag: 1771013347-123674 X-HE-Meta: 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 XyZmY5yt T24YisS1iElrQFcyDpnxGJeu3VWa6O189dQqU2zLJOHGTR6QDhWeAVXLi3qJbVHUZfQe9qJu9s+KC8A2lJS8pH7lD93jnAn6RG+HcfXiLGsy+/0rJfrXqq4iKZYOpHMcIpkISc+RdllLAYN29ij/YV6SE6cY6fzfoiIo2RVXNo/Z9R0v32F6rc0tINcKBTY9wkAjpljZbE3lCE7WQX97VyUPhYw6KNi82KsarnaArFNrPq8roiWQFreSRtpk3frySGq7euyhm2ZcukRpXRhrVfTaqtnHwk9yGoDonZ5lz1oDpNci2CrE3Pyi6MYo4E7DEiWa2ak5QzkiuJtcZeS/o3s5xgBhk7pLPeLFz+Cw+J+R7RivxP0qCDVsDJqVo8KaGxyvGgP8m6Qs79K0/WTIAuQO+xm9Rv3LG/hlAsN542X7nwcNmyakOPpex8lo7td2ixbZb84vUHitcyn0= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, Feb 13, 2026 at 06:03:32PM +0800, Kairui Song wrote: > From: Kairui Song > > We currently have two different sets of helpers for getting or putting > the private IDs' refcount for order 0 and large folios. This is > redundant. Just use one and always acquire the refcount of the swapout > folio size unless it's zero, and put the refcount using the folio size > if the charge failed, since the folio size can't change. Then there is > no need to update the refcount for tail pages. > > Same for freeing, then only one pair of get/put helper is needed now. > > The performance might be slightly better, too: both "inc unless zero" > and "add unless zero" use the same cmpxchg implementation. For large > folios, we saved an atomic operation. And for both order 0 and large > folios, we saved a branch. > > Signed-off-by: Kairui Song Nice improvement! Acked-by: Johannes Weiner