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 B8868C433EF for ; Mon, 24 Jan 2022 13:16:17 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 4D4856B007B; Mon, 24 Jan 2022 08:16:17 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 45DA76B007D; Mon, 24 Jan 2022 08:16:17 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 2D7C16B0081; Mon, 24 Jan 2022 08:16:17 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0098.hostedemail.com [216.40.44.98]) by kanga.kvack.org (Postfix) with ESMTP id 1A96F6B007B for ; Mon, 24 Jan 2022 08:16:17 -0500 (EST) Received: from smtpin16.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id C1D9D92EBE for ; Mon, 24 Jan 2022 13:16:16 +0000 (UTC) X-FDA: 79065229152.16.29F126B Received: from mail-ua1-f45.google.com (mail-ua1-f45.google.com [209.85.222.45]) by imf31.hostedemail.com (Postfix) with ESMTP id 833512006C for ; Mon, 24 Jan 2022 13:16:14 +0000 (UTC) Received: by mail-ua1-f45.google.com with SMTP id c36so30825454uae.13 for ; Mon, 24 Jan 2022 05:16:14 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=googlemail.com; s=20210112; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=uFYFObtMXp4GI0dEMvK7PEdd9wIdRLdqU+u9A0WaZIA=; b=AQbRmLRorqGKzoH9vLmyLlfDixBs7gF2+oUApSmm1/GGJBzjvJIldKiApYcjNsUclQ ajXVlxvH6aDmRTBEoqjgTIE/42gtY0ABpIeYTGDlZwn468ogNm71jP++qoH+gHhtIyQM YZ08wNyNdcDrV3ELP/FJ/3GX5lTGN+/x4S8UyfHtjrEwt4g9NoSLSpy9GSmDuqdh6j7S v5T3W9nb9tlXDeq95xSoejHmPy+2Y1YVNt6GFLyRBh5EsGt5lyR7aNBC6eZNbn+MK4G1 XQFwH2PGabpNqtTBNrO9aRYzWa7k2OdHNGP+2K5yjogT0i4hB0yQATS2hRcohP7QrDCg MfgQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=uFYFObtMXp4GI0dEMvK7PEdd9wIdRLdqU+u9A0WaZIA=; b=qpgM1vfs7AodmNUiMlevzaisy/zIVyKWQV0RY+3KJlKeZEsPCVcX36x1yVTSSRPg4y Q0tDj+YIwGh1gHs9n70TWTOHGeLG4yQkjy2HQ197i7EwXvPcTEZQTujLpEh2gHCx2lea TlznLfQAZwrqmuonF2u6KWN1D/Zgwv3YXxE0UyuKHTidmSJfoX1r7tBDkuEZ5eF3vDoT l/g4CCCMFctHOHac5O5/gXzQ+Mk7uxIOJariFHJQmaT/NvWcJV9+mHyUKna3LHZBpdNz RdvASqUw+LJCT0WLAQsqqHBO3QmbdB/90xdPJkaZx0sB1cnDgMfcg8XkIHDFptpdBU50 tf3w== X-Gm-Message-State: AOAM533k8KD363u8UikXA5rA2nR70cOJVPOjDxyioHpXPxQdXHV/gYMV UnRJ7WpqAfokZyP/KhzDDNF/roCL+4dY3xe3Xd0= X-Google-Smtp-Source: ABdhPJwZbWpaN+safEC1+Xt9t6p1mtVWx+ZXEjvmjqHuVecNAyRAteVrjGZcrtQ52ob56AX/j11Px/cD3Ikwit4TDR4= X-Received: by 2002:a05:6102:3913:: with SMTP id e19mr5463896vsu.14.1643030173736; Mon, 24 Jan 2022 05:16:13 -0800 (PST) MIME-Version: 1.0 References: <164299573337.26253.7538614611220034049.stgit@noble.brown> <164299611278.26253.14950274629759580371.stgit@noble.brown> In-Reply-To: <164299611278.26253.14950274629759580371.stgit@noble.brown> From: Mark Hemment Date: Mon, 24 Jan 2022 13:16:02 +0000 Message-ID: Subject: Re: [PATCH 09/23] MM: submit multipage reads for SWP_FS_OPS swap-space To: NeilBrown Cc: Trond Myklebust , Anna Schumaker , Chuck Lever , Andrew Morton , Mel Gorman , Christoph Hellwig , David Howells , linux-nfs@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Authentication-Results: imf31.hostedemail.com; dkim=pass header.d=googlemail.com header.s=20210112 header.b=AQbRmLRo; dmarc=pass (policy=quarantine) header.from=googlemail.com; spf=pass (imf31.hostedemail.com: domain of markhemm@googlemail.com designates 209.85.222.45 as permitted sender) smtp.mailfrom=markhemm@googlemail.com X-Stat-Signature: 3r893u7rhwjky7c893tusnqa3ym8op4r X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 833512006C X-HE-Tag: 1643030174-612287 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 Jan 2022 at 03:52, NeilBrown wrote: > > swap_readpage() is given one page at a time, but maybe called repeatedly > in succession. > For block-device swapspace, the blk_plug functionality allows the > multiple pages to be combined together at lower layers. > That cannot be used for SWP_FS_OPS as blk_plug may not exist - it is > only active when CONFIG_BLOCK=y. Consequently all swap reads over NFS > are single page reads. > > With this patch we pass in a pointer-to-pointer when swap_readpage can > store state between calls - much like the effect of blk_plug. After > calling swap_readpage() some number of times, the state will be passed > to swap_read_unplug() which can submit the combined request. > > Some caller currently call blk_finish_plug() *before* the final call to > swap_readpage(), so the last page cannot be included. This patch moves > blk_finish_plug() to after the last call, and calls swap_read_unplug() > there too. > > Signed-off-by: NeilBrown > --- > mm/madvise.c | 8 +++- > mm/memory.c | 2 + > mm/page_io.c | 102 +++++++++++++++++++++++++++++++++++-------------------- > mm/swap.h | 16 +++++++-- > mm/swap_state.c | 19 +++++++--- > 5 files changed, 98 insertions(+), 49 deletions(-) > ... > diff --git a/mm/page_io.c b/mm/page_io.c > index 6e32ca35d9b6..bcf655d650c8 100644 > --- a/mm/page_io.c > +++ b/mm/page_io.c > @@ -390,46 +391,60 @@ int __swap_writepage(struct page *page, struct writeback_control *wbc, > static void sio_read_complete(struct kiocb *iocb, long ret) > { > struct swap_iocb *sio = container_of(iocb, struct swap_iocb, iocb); > - struct page *page = sio->bvec.bv_page; > - > - if (ret != 0 && ret != PAGE_SIZE) { > - SetPageError(page); > - ClearPageUptodate(page); > - pr_alert_ratelimited("Read-error on swap-device\n"); > - } else { > - SetPageUptodate(page); > - count_vm_event(PSWPIN); > + int p; > + > + for (p = 0; p < sio->pages; p++) { > + struct page *page = sio->bvec[p].bv_page; > + if (ret != 0 && ret != PAGE_SIZE * sio->pages) { > + SetPageError(page); > + ClearPageUptodate(page); > + pr_alert_ratelimited("Read-error on swap-device\n"); > + } else { > + SetPageUptodate(page); > + count_vm_event(PSWPIN); > + } > + unlock_page(page); > } > - unlock_page(page); > mempool_free(sio, sio_pool); > } Trivial: on success, could be single call to count_vm_events(PSWPIN, sio->pages). Similar comment for PSWPOUT in sio_write_complete() > > -static int swap_readpage_fs(struct page *page) > +static void swap_readpage_fs(struct page *page, > + struct swap_iocb **plug) > { > struct swap_info_struct *sis = page_swap_info(page); > - struct file *swap_file = sis->swap_file; > - struct address_space *mapping = swap_file->f_mapping; > - struct iov_iter from; > - struct swap_iocb *sio; > + struct swap_iocb *sio = NULL; > loff_t pos = page_file_offset(page); > - int ret; > - > - sio = mempool_alloc(sio_pool, GFP_KERNEL); > - init_sync_kiocb(&sio->iocb, swap_file); > - sio->iocb.ki_pos = pos; > - sio->iocb.ki_complete = sio_read_complete; > - sio->bvec.bv_page = page; > - sio->bvec.bv_len = PAGE_SIZE; > - sio->bvec.bv_offset = 0; > > - iov_iter_bvec(&from, READ, &sio->bvec, 1, PAGE_SIZE); > - ret = mapping->a_ops->swap_rw(&sio->iocb, &from); > - if (ret != -EIOCBQUEUED) > - sio_read_complete(&sio->iocb, ret); > - return ret; > + if (*plug) > + sio = *plug; 'plug' can be NULL when called from do_swap_page(); if (plug && *plug) Cheers, Mark