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 776E5C4332F for ; Tue, 22 Nov 2022 03:42:28 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id CCCEE6B0071; Mon, 21 Nov 2022 22:42:27 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id C55F16B0073; Mon, 21 Nov 2022 22:42:27 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id ACF738E0002; Mon, 21 Nov 2022 22:42:27 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0014.hostedemail.com [216.40.44.14]) by kanga.kvack.org (Postfix) with ESMTP id 99C416B0071 for ; Mon, 21 Nov 2022 22:42:27 -0500 (EST) Received: from smtpin12.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay08.hostedemail.com (Postfix) with ESMTP id 6A3B314040B for ; Tue, 22 Nov 2022 03:42:27 +0000 (UTC) X-FDA: 80159680734.12.FD17F27 Received: from mail-pf1-f174.google.com (mail-pf1-f174.google.com [209.85.210.174]) by imf17.hostedemail.com (Postfix) with ESMTP id EBE5B4000E for ; Tue, 22 Nov 2022 03:42:26 +0000 (UTC) Received: by mail-pf1-f174.google.com with SMTP id g62so13177466pfb.10 for ; Mon, 21 Nov 2022 19:42:26 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc:subject:date:message-id:reply-to; bh=AptSfaygHWZ6DJuwqcME0BS6j60WJD3D2GSMZmjS0iI=; b=DpSgZ5Mms4nVtop5BPuClMCwDJZqnFZrxxGyEjuUGMUeayLoFaOrapYYFcDWKUV7W+ LH8VlUgWhA/u/nF6uiIixkqv1+i6rp9E54GPOHhM7h3uuZ+fpV2qb+q6luUSeyBl3cgF KvgqZMk9WQa6fk8SluhrHqtcvxxRBY4ObaOoE= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=AptSfaygHWZ6DJuwqcME0BS6j60WJD3D2GSMZmjS0iI=; b=1HmqsRExOOTTUW2vrEc3gzLSGk8LtIC8Jcx34pOyY2FiJYqbStw5F2a2pBTayezuMZ PrNZXl29OaafXCnEiQs4tqKofWxWoWhHJQBPPJCbcf2pMjnbhFnE2MqlviTLt4dOgOZY ToVpokNqTg5RZjVhbzcdGWwz/HeDqbAnY6fA5frLBtp/aFLbIrLNgMkMgxRoubmdzYZa Wr1paJ60iUeIyCt/OGOQ8halzgYWbot4JvFyT3R4XtU/jnLFwpTpLM7uQ66AMOk1TYK9 FF/gTSCmdautLMyFbbXMVP1p2/+Ntrn5zejRoJwzRqZdGORYTsY05Kn8GsztHiooWjtN BDkA== X-Gm-Message-State: ANoB5plA2hSiV+9jApb8RS9cz89PUJEOaYZDJj0YBnQHHlldvmuKwpvZ KoFZURO0iC5PgugRfFx7peH0Rg== X-Google-Smtp-Source: AA0mqf6h3Trq07ulGD7Jl9vpfTiBEXj+K33xYktk0xDOZmwxPrg2Y4mBXv5YfbRMIyHR9QLoNq70Ww== X-Received: by 2002:a05:6a00:338c:b0:56b:a319:7b52 with SMTP id cm12-20020a056a00338c00b0056ba3197b52mr3135785pfb.21.1669088545928; Mon, 21 Nov 2022 19:42:25 -0800 (PST) Received: from google.com ([240f:75:7537:3187:e258:71ac:37b7:2d52]) by smtp.gmail.com with ESMTPSA id d12-20020a170902654c00b0017f5ba1fffasm6051055pln.297.2022.11.21.19.42.22 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 21 Nov 2022 19:42:25 -0800 (PST) Date: Tue, 22 Nov 2022 12:42:20 +0900 From: Sergey Senozhatsky To: Johannes Weiner Cc: Sergey Senozhatsky , Nhat Pham , akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, minchan@kernel.org, ngupta@vflare.org, sjenning@redhat.com, ddstreet@ieee.org, vitaly.wool@konsulko.com Subject: Re: [PATCH v6 6/6] zsmalloc: Implement writeback mechanism for zsmalloc Message-ID: References: <20221119001536.2086599-1-nphamcs@gmail.com> <20221119001536.2086599-7-nphamcs@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: ARC-Authentication-Results: i=1; imf17.hostedemail.com; dkim=pass header.d=chromium.org header.s=google header.b=DpSgZ5Mm; spf=pass (imf17.hostedemail.com: domain of senozhatsky@chromium.org designates 209.85.210.174 as permitted sender) smtp.mailfrom=senozhatsky@chromium.org; dmarc=pass (policy=none) header.from=chromium.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1669088547; a=rsa-sha256; cv=none; b=Dj4t/UH3d1NJ+jrgj6MGaVL3sBBqNNPm2PabcaF2VwFJj+I8hjd37F2u+BEyYAP4r3BCIv KwJ67+f9hYH6Ib1oN1xYveLPS96YlvmjxHjYtwxrDHK20luZAMM8ERZZTUfDmCLkww2Ydq 0LApnJYwc+XA3oUfVxmlLx4A4996u1Y= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1669088547; 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=AptSfaygHWZ6DJuwqcME0BS6j60WJD3D2GSMZmjS0iI=; b=vkwTzw8oBJsRaf77fVmNWqCui2P1QUhUH7K5wIfP5W0TtvZrtV3eGvjDamlemmRzDI+34n /yxp/3WsjCr5oNBDkB5XsQ7XAhy9yyBtu3zUpwMKIJOF1FGyo02fMhaAINegaQpgxDd8dM GkxJRtljip6HiJggPN6STEi5OKCbCkM= X-Stat-Signature: keh3d745dd7yn77h4jwkqobo9q9jy5wg X-Rspamd-Server: rspam08 X-Rspam-User: Authentication-Results: imf17.hostedemail.com; dkim=pass header.d=chromium.org header.s=google header.b=DpSgZ5Mm; spf=pass (imf17.hostedemail.com: domain of senozhatsky@chromium.org designates 209.85.210.174 as permitted sender) smtp.mailfrom=senozhatsky@chromium.org; dmarc=pass (policy=none) header.from=chromium.org X-Rspamd-Queue-Id: EBE5B4000E X-HE-Tag: 1669088546-48247 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 (22/11/21 22:12), Johannes Weiner wrote: > On Tue, Nov 22, 2022 at 11:15:20AM +0900, Sergey Senozhatsky wrote: > > On (22/11/18 16:15), Nhat Pham wrote: > > > + > > > +static int zs_zpool_shrink(void *pool, unsigned int pages, > > > + unsigned int *reclaimed) > > > +{ > > > + unsigned int total = 0; > > > + int ret = -EINVAL; > > > + > > > + while (total < pages) { > > > + ret = zs_reclaim_page(pool, 8); > > > + if (ret < 0) > > > + break; > > > + total++; > > > + } > > > + > > > + if (reclaimed) > > > + *reclaimed = total; > > > + > > > + return ret; > > > +} > > > > A silly question: why do we need a retry loop in zs_reclaim_page()? > > Individual objects in a zspage can be busy (swapped in simultaneously > for example), which will prevent the zspage from being freed. Zswap > currently requests reclaim of one backend page at a time (another > project...), so if we don't retry we're not meeting the reclaim goal > and cause rejections for new stores. What I meant was: if zs_reclaim_page() makes only partial progress with the current LRU tail zspage and returns -EAGAIN, then we just don't increment `total` and continue looping in zs_zpool_shrink(). On each iteration zs_reclaim_page() picks the new LRU tail (if any) and tries to write it back. > The number 8 is cribbed from zbud and z3fold. OK.