From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5E7F8C38A2D for ; Mon, 24 Oct 2022 20:59:17 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id F35CD940008; Mon, 24 Oct 2022 16:59:16 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id EE60F940007; Mon, 24 Oct 2022 16:59:16 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id DD4E2940008; Mon, 24 Oct 2022 16:59:16 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0012.hostedemail.com [216.40.44.12]) by kanga.kvack.org (Postfix) with ESMTP id C9E8F940007 for ; Mon, 24 Oct 2022 16:59:16 -0400 (EDT) Received: from smtpin17.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay02.hostedemail.com (Postfix) with ESMTP id 9B3A4120AD6 for ; Mon, 24 Oct 2022 20:59:16 +0000 (UTC) X-FDA: 80057058312.17.880745F Received: from sin.source.kernel.org (sin.source.kernel.org [145.40.73.55]) by imf12.hostedemail.com (Postfix) with ESMTP id C1BD74000A for ; Mon, 24 Oct 2022 20:59:15 +0000 (UTC) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by sin.source.kernel.org (Postfix) with ESMTPS id 703CCCE13CF; Mon, 24 Oct 2022 20:59:12 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5DF48C433D6; Mon, 24 Oct 2022 20:59:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1666645150; bh=yQKyqeoLs5Rv47Fo2GBbipvsMxYrxQQpfG+tX/laYm4=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=UPDkTSMdn3Ykg67g2S3qzDNAnUiqxUqv8UEV55E3bTEz6YSFU3j+liJGol4U3v3iY JjWeXaKYmPNXYxbQKZk9aPk1AaJMwDlO0R6KT7ejC2+ybylDkbLqdtDH8Csj3Pcwbm NS9IypiL/mJH3oYVAPiKWA5DpZqLHFTzpYAyFy8s= Date: Mon, 24 Oct 2022 13:59:09 -0700 From: Andrew Morton To: Alexey Romanov Cc: , , , , , Subject: Re: [PATCH v1] zram: add size class equals check into recompression Message-Id: <20221024135909.e351a2dde4eea521f359a04b@linux-foundation.org> In-Reply-To: <20221024120942.13885-1-avromanov@sberdevices.ru> References: <20221024120942.13885-1-avromanov@sberdevices.ru> X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.33; x86_64-redhat-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1666645156; 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:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=IwAU23vyCHGpTJiHJgjyMidi5xJHPSgbFd33+oetRSo=; b=WdfKd6+uPHE2Y1vHfw3DGh8JlUkbBuh83kiJ8TgNMq+KS+QZ7BFEYZqjI8kNOjL4zoiuGc ptnMAADXrQGpeUQ37+P+mkBRNMMbyvE6wH+HbYOoQDJNGOSDZGqvpSRQzlTdxnKuT6NciH iV0DGNIWL/WE4lQslHGmokv1kg9wcn8= ARC-Authentication-Results: i=1; imf12.hostedemail.com; dkim=pass header.d=linux-foundation.org header.s=korg header.b=UPDkTSMd; spf=pass (imf12.hostedemail.com: domain of akpm@linux-foundation.org designates 145.40.73.55 as permitted sender) smtp.mailfrom=akpm@linux-foundation.org; dmarc=none ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1666645156; a=rsa-sha256; cv=none; b=l4D/Q6lbcBNwO7WNW6NbMB5FIOAfzHiA+Uh26/xWlPaO2FkXRsWn/gEIaBXjDN2MAAMJ3M LWmFatSF6YmbSGk4eYIAtY7hfOs7lfcz515gRnQFon7EJ8YGO1E8BmJceZMq3/VOhtLI7D mBlbpQKc+KnJVUSEfVjXEttfyHe4Xic= X-Rspamd-Queue-Id: C1BD74000A Authentication-Results: imf12.hostedemail.com; dkim=pass header.d=linux-foundation.org header.s=korg header.b=UPDkTSMd; spf=pass (imf12.hostedemail.com: domain of akpm@linux-foundation.org designates 145.40.73.55 as permitted sender) smtp.mailfrom=akpm@linux-foundation.org; dmarc=none X-Rspam-User: X-Rspamd-Server: rspam10 X-Stat-Signature: qpesqx3d3967easjsjxg38t5ci7rzqp6 X-HE-Tag: 1666645155-449396 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, 24 Oct 2022 15:09:42 +0300 Alexey Romanov wrote: > It makes no sense for us to recompress the object if it will > be in the same size class. We anyway don't get any memory gain. > But, at the same time, we get a CPU time overhead when inserting > this object into zspage and decompressing it afterwards. > Dumb question: is it ever possible for compression to result in an increase in size? > + class_size_next == class_size_prev || IOW, could this be >=?