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Tue, 01 Sep 2026 02:40:33 -0700 (PDT) Date: Tue, 1 Sep 2026 11:40:31 +0200 From: Michal =?utf-8?Q?Koutn=C3=BD?= To: Joshua Hahn Cc: hannes@cmpxchg.org, shakeel.butt@linux.dev, mhocko@kernel.org, roman.gushchin@linux.dev, muchun.song@linux.dev, akpm@linux-foundation.org, david@kernel.org, ljs@kernel.org, liam@infradead.org, vbabka@kernel.org, rppt@kernel.org, surenb@google.com, dev@lankhorst.se, mripard@kernel.org, nat@pixelcluster.dev, tj@kernel.org, osalvador@suse.de, cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, kernel-team@meta.com Subject: Re: [PATCH v5 7/7] mm/memcontrol: add stock to the memsw page_counter Message-ID: References: <20260831163752.2193337-1-joshua.hahnjy@gmail.com> <20260831163752.2193337-8-joshua.hahnjy@gmail.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="xo3yor5m4gjcubez" Content-Disposition: inline In-Reply-To: <20260831163752.2193337-8-joshua.hahnjy@gmail.com> X-Rspam-User: X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: EDA72160012 X-Stat-Signature: f7ue34oksxffw39kxq1u3sd7a3hx8zom X-HE-Tag: 1788255635-562208 X-HE-Meta: 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 G2D8swzN 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: --xo3yor5m4gjcubez Content-Type: text/plain; protected-headers=v1; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Subject: Re: [PATCH v5 7/7] mm/memcontrol: add stock to the memsw page_counter MIME-Version: 1.0 Hello Joshua. On Mon, Aug 31, 2026 at 09:37:51AM -0700, Joshua Hahn wrote: > Before this series, each memcg had one stock shared by all its > page_counters (memory + memsw). Now that the memcg stock was folded > into the page_counter level, give memsw its own page_counter_stock > so that it can benefit from caching charges as well. >=20 > Note that while the allocation is conditional on do_memsw_account(), > the freeing is not; the freer will only free non-NULL stocks. This > matters because do_memsw_account() could have changed in between the > allocation and the free. (Just a passerby comment, I have no remarks to the overhaul.) The change of do_memsw_account() is because of re-attaching the memory controller between v1 and v2 trees. That's not so common operation (but not ruled out), pre-condition for that is that there's only a single online memcg, namely the root memcg. So it needs treatment especially at memcg offlining (which is what drain_all_stock() (also) does). I don't know how expensive page_counter_drain_stock_async() is going to be [1] but the v1 parts here could could be guarded with !cgroup_on_dfl(memcg->css.cgroup). Regards, Michal [1] Now, I see in 5/7 that there's the counter->stock check which should be quick bailout on v2 (maybe quicker than the cgroup_on_dfl() I=A0proposed above). --xo3yor5m4gjcubez Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iJEEABYKADkWIQRCE24Fn/AcRjnLivR+PQLnlNv4CAUCapadjBsUgAAAAAAEAA5t YW51MiwyLjUrMS4xMiwyLDIACgkQfj0C55Tb+AiQnQEAn+3D5Q8gH9HbW/icWG8F xGfgUIWouB8aOWqljr/HvZ8BANwLXDa9DIP7tkMWmP7WhMnwN1qjocussmXJE+Bl QhQK =VQ9y -----END PGP SIGNATURE----- --xo3yor5m4gjcubez--