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Howlett" , Usama Arif , Kiryl Shutsemau , Dave Chinner , Roman Gushchin , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v3 6/7] mm: list_lru: introduce folio_memcg_list_lru_alloc() Message-ID: References: <20260318200352.1039011-1-hannes@cmpxchg.org> <20260318200352.1039011-7-hannes@cmpxchg.org> <58ea360a-54e1-468e-99b5-57b716026088@lucifer.local> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Queue-Id: D9E9420003 X-Stat-Signature: zi1667kwpggyoonjus1iryr65cgfxmtp X-Rspam-User: X-Rspamd-Server: rspam04 X-HE-Tag: 1775054594-248561 X-HE-Meta: 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 YsSSAxp/ b+ngXgGdikNJaPFwZhuM3zaPrZA+HYs2F03rat0o1EdB1J+KD71j2qM22uVsypAnITjEjWQAhgD3S1Ip/xmZc52/cbfPJgIjvuAG5BKiAVNf0JhpER/sdzvU7I+oeZm6IbhbE6KQChoM4rLtzCmYg6uZNjIsmZF1Cas/96M8j1KZ3FPgla/fNA+8g5n9sA2gD8T2DIHS0/G9qFBUpM4rz1LSca3Chq9wOATeokdoBQoHut6PWAQIE7gDp49WOaAp+90gLHzRIwSlXhc3r1esptJF3p/jUEgZz/ft4P5oiEGGLaXMXjGbrQFg4PSCQzK8DW9suJyIykwQsQjEscsq3eCZD8A== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, Mar 30, 2026 at 12:54:28PM -0400, Johannes Weiner wrote: > On Tue, Mar 24, 2026 at 12:01:55PM +0000, Lorenzo Stoakes (Oracle) wrote: > > On Wed, Mar 18, 2026 at 03:53:24PM -0400, Johannes Weiner wrote: > > > memcg_list_lru_alloc() is called every time an object that may end up > > > on the list_lru is created. It needs to quickly check if the list_lru > > > heads for the memcg already exist, and allocate them when they don't. > > > > > > Doing this with folio objects is tricky: folio_memcg() is not stable > > > and requires either RCU protection or pinning the cgroup. But it's > > > desirable to make the existence check lightweight under RCU, and only > > > pin the memcg when we need to allocate list_lru heads and may block. > > > > > > In preparation for switching the THP shrinker to list_lru, add a > > > helper function for allocating list_lru heads coming from a folio. > > > > > > Reviewed-by: David Hildenbrand (Arm) > > > Signed-off-by: Johannes Weiner > > > > Logic LGTM, but would be nice to have some kdoc. With that addressed, feel free > > to add: > > > > Reviewed-by: Lorenzo Stoakes (Oracle) > > Thanks! > > > > include/linux/list_lru.h | 12 ++++++++++++ > > > mm/list_lru.c | 39 ++++++++++++++++++++++++++++++++++----- > > > 2 files changed, 46 insertions(+), 5 deletions(-) > > > > > > diff --git a/include/linux/list_lru.h b/include/linux/list_lru.h > > > index 4afc02deb44d..4bd29b61c59a 100644 > > > --- a/include/linux/list_lru.h > > > +++ b/include/linux/list_lru.h > > > @@ -81,6 +81,18 @@ static inline int list_lru_init_memcg_key(struct list_lru *lru, struct shrinker > > > > > > int memcg_list_lru_alloc(struct mem_cgroup *memcg, struct list_lru *lru, > > > gfp_t gfp); > > > + > > > +#ifdef CONFIG_MEMCG > > > +int folio_memcg_list_lru_alloc(struct folio *folio, struct list_lru *lru, > > > + gfp_t gfp); > > > > Could we have a kdoc comment for this? Thanks! > > And one kdoc comment. > > Your total will be 8.75, you can pull up to the next window, sir. :>) Thanks!