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Sun, 13 Nov 2022 23:55:21 -0800 (PST) Date: Mon, 14 Nov 2022 16:55:17 +0900 From: Sergey Senozhatsky To: Minchan Kim Cc: Sergey Senozhatsky , Andrew Morton , Nitin Gupta , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCHv4 0/9] zsmalloc/zram: configurable zspage size Message-ID: References: <20221031054108.541190-1-senozhatsky@chromium.org> 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=1668412523; a=rsa-sha256; cv=none; b=PPPzPQ3FpT/D1UCdSY/J/akJXfdZzCuYLa0hfB3ncws0AzxgkOZbQhPpS8oY+RyGoRpV/n r3ZeLnzA7OUwWECk9MkC8eCLfFwEtXQC2OrhfsDu/kbNMZ8af7tR1mCzJOdudK1cmKgyiI OTNwcYLkGJv/uH4eTkkvzUbDKl3jIss= ARC-Authentication-Results: i=1; imf07.hostedemail.com; dkim=pass header.d=chromium.org header.s=google header.b=mOMrIe+o; dmarc=pass (policy=none) header.from=chromium.org; spf=pass (imf07.hostedemail.com: domain of senozhatsky@chromium.org designates 209.85.210.170 as permitted sender) smtp.mailfrom=senozhatsky@chromium.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1668412523; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=3q+0J39HH+ytN1oOmq1JKm/33rMfJPN2f5MEE5zjj+w=; b=JJeGKTkarjE3Z1GGYXFfnkNBySYVDJeEkkztQ6uUz6yFlnhBrUzm4BPd7S1fzLfsJ254mv X8UTvJQ+WgPfYdH4FY9GGCM6qj5VL6OZ1rn3iwFwEM7TrDgREkyawvmHQbn8T8wESicWUp /Vv8Ej7wciEft0PiwCDhrqb5P76OrIc= X-Rspamd-Queue-Id: 65AC340006 Authentication-Results: imf07.hostedemail.com; dkim=pass header.d=chromium.org header.s=google header.b=mOMrIe+o; dmarc=pass (policy=none) header.from=chromium.org; spf=pass (imf07.hostedemail.com: domain of senozhatsky@chromium.org designates 209.85.210.170 as permitted sender) smtp.mailfrom=senozhatsky@chromium.org X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: 1bbjugqoram1oow5wr43z97ejjptufct X-HE-Tag: 1668412523-381481 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 (22/11/11 09:03), Minchan Kim wrote: [..] > Only concern with bigger pages_per_zspage(e.g., 8 or 16) is exhausting memory > when zram is used for swap. The use case aims to help memory pressure but the > worst case, the bigger pages_per_zspage, more chance to out of memory. It's hard to speak in concrete terms here. What locally may look like a less optimal configuration, can result in a more optimal configuration globally. Yes, some zspage_chains get longer, but in return we have very different clustering and zspool performance/configuration. Example, a synthetic test on my host. zspage_chain_size 4 ------------------- zsmalloc classes class size almost_full almost_empty obj_allocated obj_used pages_used pages_per_zspage freeable ... Total 13 51 413836 412973 159955 3 zram mm_stat 1691783168 628083717 655175680 0 655175680 60 0 34048 34049 zspage_chain_size 8 ------------------- zsmalloc classes class size almost_full almost_empty obj_allocated obj_used pages_used pages_per_zspage freeable ... Total 18 87 414852 412978 156666 0 zram mm_stat 1691803648 627793930 641703936 0 641703936 60 0 33591 33591 Note that we have lower "pages_used" value for the same amount of stored data. Down to 156666 from 159955 pages. So it *could be* that longer zspage_chains can be beneficial even in memory sensitive cases, but we need more data on this, so that we can speak "statistically".