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 4C1CDE77188 for ; Mon, 6 Jan 2025 04:59:19 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 7779D6B0082; Sun, 5 Jan 2025 23:59:18 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 727B86B0088; Sun, 5 Jan 2025 23:59:18 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 5EF376B0089; Sun, 5 Jan 2025 23:59:18 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0013.hostedemail.com [216.40.44.13]) by kanga.kvack.org (Postfix) with ESMTP id 3FECF6B0082 for ; Sun, 5 Jan 2025 23:59:18 -0500 (EST) Received: from smtpin19.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay06.hostedemail.com (Postfix) with ESMTP id A67A3AEBE8 for ; Mon, 6 Jan 2025 04:59:17 +0000 (UTC) X-FDA: 82975823154.19.EEE8B5B Received: from out30-118.freemail.mail.aliyun.com (out30-118.freemail.mail.aliyun.com [115.124.30.118]) by imf12.hostedemail.com (Postfix) with ESMTP id 916AB4000B for ; Mon, 6 Jan 2025 04:59:14 +0000 (UTC) Authentication-Results: imf12.hostedemail.com; dkim=pass header.d=linux.alibaba.com header.s=default header.b=LSTHUvZ1; spf=pass (imf12.hostedemail.com: domain of baolin.wang@linux.alibaba.com designates 115.124.30.118 as permitted sender) smtp.mailfrom=baolin.wang@linux.alibaba.com; dmarc=pass (policy=none) header.from=linux.alibaba.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1736139555; a=rsa-sha256; cv=none; b=Ypjq0YMpo2kWqG46QDK0fB44qbuIVVABk7idr2Yp/JrLANR/GBfpGhd3ji3lBH145xamJo w6CQ0UG9l0bT4cgEwNyShC07suj0NDKxzjuB/i9x+JH1YXkaPKx+9l9mGvPCuAnBPylpyd zRFDAqVa9SBMXU6H/JzauTxtYIbQEbY= ARC-Authentication-Results: i=1; imf12.hostedemail.com; dkim=pass header.d=linux.alibaba.com header.s=default header.b=LSTHUvZ1; spf=pass (imf12.hostedemail.com: domain of baolin.wang@linux.alibaba.com designates 115.124.30.118 as permitted sender) smtp.mailfrom=baolin.wang@linux.alibaba.com; dmarc=pass (policy=none) header.from=linux.alibaba.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1736139555; 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=0oefN+xu13nE8jpyMKiHLPBwh/n+XfBGQdSn8o6rKB4=; b=gf9Q6AxFhCRP26xV8dOl+WBbo2ZmjJw9SEilEfm4j1SgvYsnUpMS4Apqa0c6cjR9Q9on0K cr6FP0hfExMteW33S87nhjmmjHgtqBK/YGqQpTuneILIyIIH6wrjCMsAwUCs1IqhtmSzky W52TQAwBx+QRpVtPz6Nd4ziIzo9eqUY= DKIM-Signature:v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.alibaba.com; s=default; t=1736139551; h=Message-ID:Date:MIME-Version:Subject:To:From:Content-Type; bh=0oefN+xu13nE8jpyMKiHLPBwh/n+XfBGQdSn8o6rKB4=; b=LSTHUvZ1ZaS6ltpt1Lnm80tLIu4UoPACmEK/Qg9FxfxowcQ+qxf279PENrX4r4knmyJH8mhnRrLw1hulFQGk7d2vy3y5M76c27+YA8fa0P203PEAdhfJLFIbEe6AY2hve7xPpbV6N70Tod/zmu/g/k41eOCmWwgV2mJJVhWqSJk= Received: from 30.74.144.118(mailfrom:baolin.wang@linux.alibaba.com fp:SMTPD_---0WN-XEjN_1736139549 cluster:ay36) by smtp.aliyun-inc.com; Mon, 06 Jan 2025 12:59:10 +0800 Message-ID: Date: Mon, 6 Jan 2025 12:59:09 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] mm: shmem: skip swapcache for swapin of synchronous swap device To: Matthew Wilcox Cc: akpm@linux-foundation.org, hughd@google.com, david@redhat.com, wangkefeng.wang@huawei.com, kasong@tencent.com, ying.huang@linux.alibaba.com, 21cnbao@gmail.com, ryan.roberts@arm.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <04997e54c276eff40a6119a90d36a4e71aade89c.1735806921.git.baolin.wang@linux.alibaba.com> <8344980d-4c22-4694-9a76-2e5a7ada50cb@linux.alibaba.com> From: Baolin Wang In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 916AB4000B X-Stat-Signature: 3rxmibgmbybgextb7zmi4j7b31mh8r9z X-Rspam-User: X-Rspamd-Server: rspam09 X-HE-Tag: 1736139554-536208 X-HE-Meta: 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 LxvwQw4o C4VSG1hEGr5N+bxu8VayhAqS5Qyx5aP0U/wA/bcZII3zI5w6OkjS/Hmy8Hf1pISul22dzbcjLSyw1luoBogM3/UlLXS3crDYnRAL5PDFaJdkOJZHMOmj/sEWZv4ncCdUCKmqmR9RilzajellK0XWu7GwaMRB3YjE02cXNNHOaQkxeNcT0OBtozAwfseg4eAckeNma/rtkco2J1+p7kzTSr8uEV2n4/x03Fey7xiU21+2uRgvKWHxXV70mwruIc4Vpn4Uq X-Bogosity: Ham, tests=bogofilter, spamicity=0.000005, 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 2025/1/6 12:07, Matthew Wilcox wrote: > On Mon, Jan 06, 2025 at 11:46:04AM +0800, Baolin Wang wrote: >> On 2025/1/2 21:10, Matthew Wilcox wrote: >>> On Thu, Jan 02, 2025 at 04:40:17PM +0800, Baolin Wang wrote: >>>> With fast swap devices (such as zram), swapin latency is crucial to applications. >>>> For shmem swapin, similar to anonymous memory swapin, we can skip the swapcache >>>> operation to improve swapin latency. >>> >>> OK, but now we have more complexity. Why can't we always skip the >>> swapcache on swapin? >> >> Skipping swapcache is used to swap-in shmem large folios, avoiding the large >> folios being split. Meanwhile, since the IO latency of syncing swap devices >> is relatively small, it won't cause the IO latency amplification issue. >> >> But for async swap devices, if we swap-in the large folio one-time, I am >> afraid the IO latency can be amplified. And I remember we still haven't >> reached an agreement here[1], so let's step by step and start with the sync >> swap devices first. > > Regardless of whether we choose to swap-in an order-0 or a large folio, > my point is that we should always do it to the pagecache rather than the > swap cache. IMO, this would miss the swap readahead algorithm in the swap case, which can benefit the order-0 swap-in. We need more work to ensure that skipping swapcache is helpful for all cases, which is why I'm starting with sync swap devices first.