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]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id DF0ADCFA468 for ; Fri, 21 Nov 2025 08:24:09 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 462A56B00A2; Fri, 21 Nov 2025 03:24:09 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 413596B00A3; Fri, 21 Nov 2025 03:24:09 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 350726B00A4; Fri, 21 Nov 2025 03:24:09 -0500 (EST) 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 249CC6B00A2 for ; Fri, 21 Nov 2025 03:24:09 -0500 (EST) Received: from smtpin30.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay02.hostedemail.com (Postfix) with ESMTP id B550D13B1F3 for ; Fri, 21 Nov 2025 08:24:08 +0000 (UTC) X-FDA: 84133926576.30.3DC8CFC Received: from out162-62-57-64.mail.qq.com (out162-62-57-64.mail.qq.com [162.62.57.64]) by imf11.hostedemail.com (Postfix) with ESMTP id 060C54000A for ; Fri, 21 Nov 2025 08:24:05 +0000 (UTC) Authentication-Results: imf11.hostedemail.com; dkim=pass header.d=foxmail.com header.s=s201512 header.b=RKQrA+iO; dmarc=pass (policy=none) header.from=foxmail.com; spf=pass (imf11.hostedemail.com: domain of ywen.chen@foxmail.com designates 162.62.57.64 as permitted sender) smtp.mailfrom=ywen.chen@foxmail.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1763713446; a=rsa-sha256; cv=none; b=2k/mnCZOX9xQgoKJu0MhD4105CLZLtDwZiUk9wQtd6FdZCI184mVTPPi8dbHroez3TSw3E 4vZAhfbnKs5+dHCKeZiMNXW4Nhu3cbJXsO6p+j3A2S2tm82H/YbelBYSoKunqa/bBbim5v lQ2UqzqHhrnVNSNCKOm+IcCDt7QOeF0= ARC-Authentication-Results: i=1; imf11.hostedemail.com; dkim=pass header.d=foxmail.com header.s=s201512 header.b=RKQrA+iO; dmarc=pass (policy=none) header.from=foxmail.com; spf=pass (imf11.hostedemail.com: domain of ywen.chen@foxmail.com designates 162.62.57.64 as permitted sender) smtp.mailfrom=ywen.chen@foxmail.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1763713446; 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-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=pQLrOq0QQR+4eVsM8YUr1bTz3EqZ74x8PaNds/2DexI=; b=dIPgc3J9Ty/udJ34qXUxTTt2UNS43+tSkajwZJtrXLuAUJ2kRLsDfchMO9wOZ6efeFjP7U vLHeA87Y/5/nZCRNmOXJFX50XmAiNgoxIizVD9CIHwUlGMv5uSbP7fcwdlD7928/6KBNUo 8MC1J/M6JktHXZLMQ7PYaPP1vj1yS5Y= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=foxmail.com; s=s201512; t=1763713441; bh=pQLrOq0QQR+4eVsM8YUr1bTz3EqZ74x8PaNds/2DexI=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=RKQrA+iOdCisookcvk14Z5yjxEmikMT3jFLMqCKPt4+GHVxIt5S81rrwrH0uEdnP6 pDuFjHcaURvWaok1m5L3XzTvVTbpvbEvZ6LSer899JgzfGRrZiMZyuDCGg1DptHrcJ 1emf01+1NNBEZcRVMxpDFc9fvAw2dIPjOm2CIyv4= Received: from meizu-Precision-3660.meizu.com ([112.91.84.72]) by newxmesmtplogicsvrszc50-0.qq.com (NewEsmtp) with SMTP id 5FB1F4E2; Fri, 21 Nov 2025 16:23:59 +0800 X-QQ-mid: xmsmtpt1763713439tj8u89r6n Message-ID: X-QQ-XMAILINFO: OeJ9zRfntlNP/nfJC+X1lO5CmizeW4R30yyEPSi+ZAOnF15s818bIUMKTLMFn2 7DXMfvxYVYiae95vc2wW1xWCDIMZzPkAgZlIkb5rzh2/JGLDZF9XSWHj5j/M1qaCu1AtVTFFjDIF O28CWP1CSOQ3k8Jb8COVsS4Ig3DDTERdRt2/Ooy4mEVwg4o2vzZOBTxQnzS0+PkBjMa+85rnHstk kVjmZTiAWY+JySl7u68j+maZDOOS9JCmQGBiHlTYvMlh801ypfiEnV8cCDz4o7BbB5ZHLuyk7ziH hooCTHufT1M0D23oQCvYW0jh6xGfPp1oP+8dFZ7F+KdTpaNkCWicrCVzrT3k6n92IO0Nyq+r8Q8Z C07AirQ3Z3pe5uoOO/zFXnWr3gr9tz3HqBdxPeaKTlW1y4oAzgOckWNpmx8jGy36K/Q+XrquUp21 UfOJHH6ykFXaOrEj0DmR2ySRx9m4hPCuOzMqewHyzbWPj2G6uRQ3St7Fort4UT7sfyYUKayEfxiN 0uDLFsRcQhyCSsCtpAry6fMfTuyAvvpBQZyeuMZs2ICo1TeMkzHdiSNUPziNQq99c3MrP8WUcOJd As5txDvdJrKaBNh1FF7XBPPtKktzN1ubcgQukzFcmtP8HuRa7UgBRDOc+IcHe6+gXXW5LXtfO7tk O4yJUHvRGGxulFxHQwIpgs3sgZekQ14hyo0XLoMeoWl1WuB8gobQqE3/9bGCVG6rVFpbjNkca5Q+ DDK4aKbojVkDKK2bYl2DiU24R4nZCZwNfeAyOyvys/YQrGKWhJdk4rnoaYgTjXnnNGLfG2XoNaCr K+1c/9puY8rEb5KEBACZqDdWzjbJCZw+f8I/WmmfGCWbPD7pKyhKAKtaHLh3sikZayCIIZGK1fXb TjQFw/+kWWqPvErQJZG/MpsmOEnTvT1YNDrGEvABOfxuZ9hhchRee+NWMiOYpI4mm/i+wwZ9S4aW FLDQYud6juRugTSEfB/9XFn6qJ6QtMG/nXwK2DOWbV7a4A5SUyL+RgdyVhWEx92TxI7FZRpQiwqu 4Q+TYgH0moYERRYOHs5vn6bv9BVzPPPpXMXVog3oh723JmWumNdWK5gWfHQKYeCt2fSGc2H89str bb/bdA9A28WRci2xS0TBKpQCkNcgRt5wjdfe+AmkfyWvYdaDGpEM7WBBUtig== X-QQ-XMRINFO: MSVp+SPm3vtS1Vd6Y4Mggwc= From: Yuwen Chen To: senozhatsky@chromium.org Cc: akpm@linux-foundation.org, bgeffon@google.com, licayy@outlook.com, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, minchan@kernel.org, richardycc@google.com, ywen.chen@foxmail.com Subject: Re: [RFC PATCHv5 0/6] zram: introduce writeback bio batching Date: Fri, 21 Nov 2025 16:23:58 +0800 X-OQ-MSGID: <20251121082358.3003848-1-ywen.chen@foxmail.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: 060C54000A X-Rspamd-Server: rspam07 X-Stat-Signature: amhy9acug4goof73spxa86ge4w4en4ne X-Rspam-User: X-HE-Tag: 1763713445-629575 X-HE-Meta: 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 Vns+OH5u BvZ9GEp1tEqSi1rWQDS5hdlHbRpFsq+FcVgB2DAd1ZiJUS+JFL1+ltamIPjuG1Peg9M1CAtmkYhOTa0vxLyF+95/yiogP1w1grfGqsSbc8UvJ3Ck4VutwzM7TFXSA9/1LkmkM16QUwOzgISFZtEcbSAv72k8kq6UgaCG67gZlpcLKe/RQOptpyjZBmvrds3Yx3M3Bv2MYZhZL3PSHtdqGRybDew== 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: List-Subscribe: List-Unsubscribe: On Fri, 21 Nov 2025 16:58:41 +0900, Sergey Senozhatsky wrote: > No problem. I wonder if the effect is more visible on larger data sets. > 0.3 second sounds like a very short write. In my VM tests I couldn't get > more than 2 inflight requests at a time, I guess because decompression > was much slower than IO. I wonder how many inflight requests you had in > your tests. I used the following code for testing here, and the result was 32. code: @@ -983,6 +983,7 @@ static int zram_writeback_slots(struct zram *zram, struct zram_pp_slot *pps; int ret = 0, err = 0; u32 index = 0; + int inflight = 0; while ((pps = select_pp_slot(ctl))) { spin_lock(&zram->wb_limit_lock); @@ -993,6 +994,9 @@ static int zram_writeback_slots(struct zram *zram, } spin_unlock(&zram->wb_limit_lock); + if (inflight < atomic_read(&wb_ctl->num_inflight)) + inflight = atomic_read(&wb_ctl->num_inflight); + while (!req) { req = zram_select_idle_req(wb_ctl); if (req) @@ -1074,6 +1078,7 @@ next: ret = err; } + pr_err("%s: inflight max: %d\n", __func__, inflight); return ret; } log: [3741949.842927] zram: zram_writeback_slots: inflight max: 32 Changing ZRAM_WB_REQ_CNT to 64 didn't shorten the overall time. > I think page-fault latency of a written-back page is expected to be > higher, that's a trade-off that we agree on. Off the top of my head, > I don't think we can do anything about it. > > Is loop device always used as for writeback targets? On the Android platform, currently only the loop device is supported as the backend for writeback, possibly for security reasons. I noticed that EROFS has implemented a CONFIG_EROFS_FS_BACKED_BY_FILE to reduce this latency. I think ZRAM might also be able to do this.