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Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Usama Arif , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH v2 1/2] mm/huge_memory: use folio's memcg inside __folio_split() Message-ID: References: <20260730-add-gfp_account-to-xas_split_alloc-v2-0-5a56c2361d85@nvidia.com> <20260730-add-gfp_account-to-xas_split_alloc-v2-1-5a56c2361d85@nvidia.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Mon, Aug 03, 2026 at 11:02:30AM -0400, Zi Yan wrote: > On Sat Aug 1, 2026 at 5:36 AM EDT, Lorenzo Stoakes (ARM) wrote: > > On Thu, Jul 30, 2026 at 10:18:00PM -0400, Zi Yan wrote: > >> During a pagecache folio split, an xarray node allocation can happen and > >> needs to charge at folio's memcg instead of folio split invoker's memcg, > >> because for example folio split can happen during reclaim and reclaim's > >> active memcg might not be folio's memcg. Switch to folio's memcg at the > >> beginning and switch back afterwards. > > > > I assume this is the only allocation? I guess in general it makes sense to have > > the folio's memcg be active here regardless. > > > >> > >> Suggested-by: Johannes Weiner > >> Fixes: 6b24ca4a1a8d4 ("mm: Use multi-index entries in the page cache") > > > > Cc: stable? > > Like you said above, only xas_split_alloc() is affected. And we have not > seen related workingset regression report (like what Johannes reported > in commit 7b785645e8f13 ("mm: fix page cache convergence regression")). > It might be OK to not backport. > > Johannes, what is your take on this? Yeah, let's Cc stable. It would be a bear to debug if you ran into this at scale. Which I think you could with certain workloads. The patches are straight-forward enough. It favors a backport.