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Wed, 22 Jul 2026 19:27:12 -0700 (PDT) Date: Wed, 22 Jul 2026 22:27:08 -0400 From: Johannes Weiner To: Hao Jia Cc: akpm@linux-foundation.org, tj@kernel.org, shakeel.butt@linux.dev, mhocko@kernel.org, yosry@kernel.org, mkoutny@suse.com, nphamcs@gmail.com, chengming.zhou@linux.dev, muchun.song@linux.dev, roman.gushchin@linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, Hao Jia Subject: Re: [PATCH v2 2/2] mm/zswap: Support batch writeback in shrink_memcg() Message-ID: References: <20260717085151.22822-1-jiahao.kernel@gmail.com> <20260717085151.22822-3-jiahao.kernel@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260717085151.22822-3-jiahao.kernel@gmail.com> X-Rspam-User: X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: AA786140005 X-Stat-Signature: u691p1s8rsgi31nk4nk8ar4ifcdrttqk X-HE-Tag: 1784773634-875459 X-HE-Meta: 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 nAfqKlb3 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, Jul 17, 2026 at 04:51:51PM +0800, Hao Jia wrote: > @@ -1369,7 +1402,7 @@ static void shrink_worker(struct work_struct *w) > goto resched; > } > > - ret = shrink_memcg(memcg); > + ret = shrink_memcg(memcg, NR_ZSWAP_WB_BATCH); > /* drop the extra reference */ > mem_cgroup_put(memcg); > > @@ -1493,7 +1526,7 @@ bool zswap_store(struct folio *folio) > objcg = get_obj_cgroup_from_folio(folio); > if (objcg && !obj_cgroup_may_zswap(objcg)) { > memcg = get_mem_cgroup_from_objcg(objcg); > - if (shrink_memcg(memcg)) { > + if (shrink_memcg(memcg, 1)) { Why 64 for the global limit but only 1 for the cgroup limit? That seems arbitrary in multiple ways. Direct reclaim, kswapd, proactive reclaim, cgroup limit reclaim use SWAP_CLUSTER_MAX for the batch size near-universally. It's magic too to be sure, but at least you wouldn't have to make up new magic? Otherwise, the patch looks good to me.