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Tue, 22 Sep 2026 06:31:31 +0000 X-Mizu-Trace-ID: 3d5eaa6d3b009fbe X-Migadu-Flow: FLOW_OUT Content-Type: text/plain; charset=us-ascii Mime-Version: 1.0 (Mac OS X Mail 16.0 \(3864.700.51.1.1\)) Subject: Re: [PATCH 2/2] mm/memcg: migrate per-node hugetlb lruvec stat together with hugetlb folio From: Muchun Song In-Reply-To: Date: Tue, 22 Sep 2026 14:31:14 +0800 Cc: Joshua Hahn , Hongfu Li , Oscar Salvador , David Hildenbrand , Andrew Morton , Shakeel Butt , Michal Hocko , Roman Gushchin , Nhat Pham , Chris Down , Johannes Weiner , Michal Hocko , linux-mm@kvack.org, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, Hongfu Li , stable@vger.kernel.org Content-Transfer-Encoding: quoted-printable Message-Id: References: <20260922042054.3264663-1-joshua.hahnjy@gmail.com> To: "Oscar Salvador (SUSE)" X-Mailer: Apple Mail (2.3864.700.51.1.1) X-Rspam-User: X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 4BACF40002 X-Stat-Signature: zruwy9scsh9f3qpko9u3tf5yrjf3o5ag X-HE-Tag: 1790058694-159905 X-HE-Meta: U2FsdGVkX1/z7pDIglYNqv+AEpCQ6RtDq4k/UIW06O9hGwQYY/V3HPiOmyIlVtg38lZ30woV4BDi8LcpstGnI0ImhEZPSTn0xgvMhe4W3hFh6p+zFqG1IBn7RhbvPn3SRXsVUDXSI2Xvy0XFPjN4xYPlJOAT9N2A2+HT+efz316tIl6xpW8pFlMOhLz1n0vVDHtynIuoCcFQ/iexZPGV6T7jPh5JBJ6i724UlTd11jgOQGVEngQDcOlOxLLhTXtmTHd3csOblNKSGsaGHJ7dadW9dwI0ONrnFhUaDcupXst0T0Wg3ZwkQFY+WQ5oxbOQWMBLfLGZgZ1T89ixkVn1pYhclFuPpi2V4LkvChqmCLw+E9y1gpNB2X3YXE4hNRhQNxrh/rfEbTTFJJJ2CfSt4ioUpTQZvgevToWo8FcSusSjJXOxoHNbmiHqYhqpzcty5PLygn7BLXdfAxFYT5xRqN4yT0eP/Zj6C55XUYDvjgWUPGZpx9O6gnLAJC7cz94UOzbW2NS56fs2t9VomM2cDHeli9+/23k38s+gQOZHTC0XXyNM9ZqJtvYqnA0wAFIdQpvhM/5QbmPIX4zOptcymFVI+qg1IHwY89b9RRY4pAfXrkrKtm6vaGr/OvFxC6IGl8CJg0UYPfkOjSIWnPjOFHG3JfHvDjZfuiwE76VIHMGu8+1Hqcu8adolp8GHJbxU2hilIApnxYovbIjq5HC7/SsbzTSqURGwj9HssqDumsACsZuTrZm0zeC86vsRdHVdyDTBhkOUvdZqRvT22heS2+rE+LKtAfdeIFVMIbab4pMpymhQsZ0hAhiYRcjwpzM74Jw732IMzf2bTNjKewgNb63PjZAMpIBSJAnxrxmJViTsCA4gwzM9Sa0iL6zHysEsU7Lh6+1szrZ5XRouB0D0i7APNCiF/OaycieETNhxZMKVNvphl//KoHR5LjdbqNPZpsFDhhxO7M/E0k5KK9P BAA5OIu9 QzyYeRa/TRI6x/Vjo6Cm1JeUiRMltEjqBy5wFc83wnV6W5L5QXYsdHMVpQ/rB8og/GuJq3mc4duitjwTMb5HOrZf1sz+kq46pWoCGZO57uN3tNFJaTbqUgHJMC+sVpuP5T1K/SjOhr9un0OchfueGKAxqCOXYI99bcE6k+wZV1twgrvyFBZ8eUYNG6f+xvB8UmAfP1FCUfdiVSw8erlK/BkE4hqCr2DlqgnxmS+Jl+f7NKw2IoCrhI3Fg2zq/C7Xt5L8+V2U8pUPXlj8mUGqE0Ds4N6G5/BdXU9xgXVcFMd0GMsQtskjuSrEnUqyYoxmFy5kTHoEAAMd1UlIRpiqDxngD9ilu92udde8h0/xAifDGkow= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: > On Sep 22, 2026, at 12:30, Oscar Salvador (SUSE) = wrote: >=20 > On Mon, Sep 21, 2026 at 09:20:53PM -0700, Joshua Hahn wrote: >> On Tue, 22 Sep 2026 06:15:07 +0200 "Oscar Salvador (SUSE)" = wrote: >=20 >>> Why do we need the whole thing to be embraced by rcu? >>=20 >> Hi Oscar, >=20 > Hi Joshua, >=20 >>=20 >> I believe it's because now getting the memcg from the objcg requires >> an RCU lock to make sure it doesn't get removed while we work on the >> memcg. I think this is since Qi Zheng's "Eliminate Dying Memory >> Cgroup" series. >=20 > Yes, I understood that obj_cgroup_memcg might need the rcu-dance, but = I was > unsure about the mod_memcg_lruvec_state() calls. The caller needs to make sure the liveness of lruvec, in which case, lruvec is from memcg, so rcu lock is needed here. Thanks, Muchun >=20 >=20 > --=20 > Oscar Salvador > SUSE Labs