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Mon, 28 Dec 2020 11:05:54 -0800 (PST) Received: from [2620:15c:17:3:4a0f:cfff:fe51:6667] ([2620:15c:17:3:4a0f:cfff:fe51:6667]) by smtp.gmail.com with ESMTPSA id o129sm35262730pfg.66.2020.12.28.11.05.53 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 28 Dec 2020 11:05:53 -0800 (PST) Date: Mon, 28 Dec 2020 11:05:53 -0800 (PST) From: David Rientjes To: Jann Horn cc: Christoph Lameter , Pekka Enberg , Joonsoo Kim , Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm, slub: Consider rest of partial list if acquire_slab() fails In-Reply-To: <20201228130853.1871516-1-jannh@google.com> Message-ID: <9b9ef131-d563-3987-88a1-1962477b2894@google.com> References: <20201228130853.1871516-1-jannh@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII 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: On Mon, 28 Dec 2020, Jann Horn wrote: > acquire_slab() fails if there is contention on the freelist of the page > (probably because some other CPU is concurrently freeing an object from the > page). In that case, it might make sense to look for a different page > (since there might be more remote frees to the page from other CPUs, and we > don't want contention on struct page). > > However, the current code accidentally stops looking at the partial list > completely in that case. Especially on kernels without CONFIG_NUMA set, > this means that get_partial() fails and new_slab_objects() falls back to > new_slab(), allocating new pages. This could lead to an unnecessary > increase in memory fragmentation. > > Fixes: 7ced37197196 ("slub: Acquire_slab() avoid loop") > Signed-off-by: Jann Horn Acked-by: David Rientjes Indeed, it looks like commit 7ced37197196 ("slub: Acquire_slab() avoid loop") stopped the iteration prematurely.