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Thu, 10 Jun 2021 01:36:38 -0700 (PDT) Received: from grain.localdomain ([5.18.171.94]) by smtp.gmail.com with ESMTPSA id z4sm95628lji.61.2021.06.10.01.36.37 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 10 Jun 2021 01:36:37 -0700 (PDT) Received: by grain.localdomain (Postfix, from userid 1000) id 651DE5A0041; Thu, 10 Jun 2021 11:36:36 +0300 (MSK) Date: Thu, 10 Jun 2021 11:36:36 +0300 From: Cyrill Gorcunov To: Vlastimil Babka Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Christoph Lameter , David Rientjes , Pekka Enberg , Joonsoo Kim , Sebastian Andrzej Siewior , Thomas Gleixner , Mel Gorman , Jesper Dangaard Brouer , Peter Zijlstra , Jann Horn Subject: Re: [RFC v2 29/34] mm: slub: Move flush_cpu_slab() invocations __free_slab() invocations out of IRQ context Message-ID: References: <20210609113903.1421-1-vbabka@suse.cz> <20210609113903.1421-30-vbabka@suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/2.0.7 (2021-05-04) Authentication-Results: imf26.hostedemail.com; dkim=pass header.d=gmail.com header.s=20161025 header.b=LM2IOt13; dmarc=pass (policy=none) header.from=gmail.com; spf=pass (imf26.hostedemail.com: domain of gorcunov@gmail.com designates 209.85.208.172 as permitted sender) smtp.mailfrom=gorcunov@gmail.com X-Rspamd-Server: rspam02 X-Stat-Signature: aokf59fbjsqoc7xdmtutb1e7j5mz6geg X-Rspamd-Queue-Id: 7B1724202A16 X-HE-Tag: 1623314197-43692 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 Thu, Jun 10, 2021 at 10:32:14AM +0200, Vlastimil Babka wrote: > >> static void flush_all(struct kmem_cache *s) > >> { > >> - on_each_cpu_cond(has_cpu_slab, flush_cpu_slab, s, 1); > >> + struct slub_flush_work *sfw; > >> + unsigned int cpu; > >> + > >> + cpus_read_lock(); > >> + mutex_lock(&flush_lock); > >> + > > > > Hi, Vlastimil! Could you please point why do you lock cpus first and > > mutex only after? Why not mutex_lock + cpus_read_lock instead? > > Good question! I must admit I didn't think about it much and just followed the > order that was in the original Sebastian's patch [1] > But there was a good reason for this order as some paths via > __kmem_cache_shutdown() and __kmem_cache_shrink() were alreadu called under > cpus_read_lock. Meanwhile mainline (me, actually) removed those, so now it > doesn't seem to be a need to keep this order anymore and we could switch it. I bet we should switch :) But we can do that on top later, once series is settled down and merged.