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Wed, 02 Nov 2022 14:36:37 -0700 (PDT) Date: Wed, 2 Nov 2022 14:36:35 -0700 From: Minchan Kim To: Sergey Senozhatsky Cc: Nhat Pham , akpm@linux-foundation.org, hannes@cmpxchg.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, ngupta@vflare.org, sjenning@redhat.com, ddstreet@ieee.org, vitaly.wool@konsulko.com Subject: Re: [PATCH 2/5] zsmalloc: Consolidate zs_pool's migrate_lock and size_class's locks Message-ID: References: <20221026200613.1031261-1-nphamcs@gmail.com> <20221026200613.1031261-3-nphamcs@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1667424999; a=rsa-sha256; cv=none; b=HRRdTk1tLhy37rDYRvkZvDy9O3VCD8m6AdbmVHPNwQtAZzyYkZ116L/zOxFJ4O/BSvluXo XIWDLgdL52M3O71QZj0DwRNMf+y+Nve2YXlg6DuTVWwKqaLJuOwukFCNNXRQd0BkR6rEMl StDbCPzJ26y4TjPEHvr912yCfhw2YIE= ARC-Authentication-Results: i=1; imf29.hostedemail.com; dkim=pass header.d=gmail.com header.s=20210112 header.b=Amp8eBSE; 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dmarc=fail reason="SPF not aligned (relaxed), DKIM not aligned (relaxed)" header.from=kernel.org (policy=none); spf=pass (imf29.hostedemail.com: domain of minchan.kim@gmail.com designates 209.85.215.170 as permitted sender) smtp.mailfrom=minchan.kim@gmail.com X-Rspam-User: X-Rspamd-Server: rspam07 X-HE-Tag: 1667424999-70030 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 Wed, Nov 02, 2022 at 12:28:56PM +0900, Sergey Senozhatsky wrote: > On (22/10/26 13:06), Nhat Pham wrote: > > struct size_class { > > - spinlock_t lock; > > struct list_head fullness_list[NR_ZS_FULLNESS]; > > /* > > * Size of objects stored in this class. Must be multiple > > @@ -247,8 +245,7 @@ struct zs_pool { > > #ifdef CONFIG_COMPACTION > > struct work_struct free_work; > > #endif > > - /* protect page/zspage migration */ > > - rwlock_t migrate_lock; > > + spinlock_t lock; > > }; > > I'm not in love with this, to be honest. One big pool lock instead > of 255 per-class locks doesn't look attractive, as one big pool lock > is going to be hammered quite a lot when zram is used, e.g. as a regular > block device with a file system and is under heavy parallel writes/reads. > I agree with Sergey. I am also worry about that LRU stuff should be part of allocator instead of higher level.