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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 03BC4C28D13 for ; Mon, 22 Aug 2022 12:02:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233689AbiHVMCI (ORCPT ); Mon, 22 Aug 2022 08:02:08 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40702 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230122AbiHVMCH (ORCPT ); Mon, 22 Aug 2022 08:02:07 -0400 Received: from smtp-out1.suse.de (smtp-out1.suse.de [195.135.220.28]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 69B222DA83 for ; Mon, 22 Aug 2022 05:02:04 -0700 (PDT) Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by smtp-out1.suse.de (Postfix) with ESMTPS id 19F0D344ED; Mon, 22 Aug 2022 12:02:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_rsa; t=1661169723; h=from:from:reply-to:reply-to:date:date:message-id:message-id:to:to: cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=+FnxzNbftSUSFX2upl+4Rx9qbpxZq0KE0laQDUGyDpU=; b=vL7oB3s/zuTN9WuV16UOFkGG/FdX+X05YJ3XhAe4OcG5iDS8Os0RhVunsR1g2IaSmwMURO vPFnV+nk78nbQ+jIntBlGQV6U8SKyfBKmUbVdjz/wBMKKtVp0enTz2+qdrsu2tFRZWSViw up4mox7b0pC4aRTtnL4+HAuVOC9AJAY= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_ed25519; t=1661169723; h=from:from:reply-to:reply-to:date:date:message-id:message-id:to:to: cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=+FnxzNbftSUSFX2upl+4Rx9qbpxZq0KE0laQDUGyDpU=; b=1sHNs22D5z9V1nnGoloVqw0ST4sLSdV6Yn3T0sAAAFGmCnBsj5W8Tto+JF2JblOOL+vYaY hOKDwgEUn8GArtDg== Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id DDF1513523; Mon, 22 Aug 2022 12:02:02 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id jTZBNTpwA2NePgAAMHmgww (envelope-from ); Mon, 22 Aug 2022 12:02:02 +0000 Date: Mon, 22 Aug 2022 13:56:49 +0200 From: David Sterba To: ethanlien Cc: linux-btrfs@vger.kernel.org, cunankimo@gmail.com Subject: Re: [PATCH v2] btrfs: remove unnecessary EXTENT_UPTODATE state in buffered I/O path Message-ID: <20220822115649.GS13489@twin.jikos.cz> Reply-To: dsterba@suse.cz Mail-Followup-To: dsterba@suse.cz, ethanlien , linux-btrfs@vger.kernel.org, cunankimo@gmail.com References: <20220819024408.9714-1-ethanlien@synology.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220819024408.9714-1-ethanlien@synology.com> User-Agent: Mutt/1.5.23.1-rc1 (2014-03-12) Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org On Fri, Aug 19, 2022 at 10:44:08AM +0800, ethanlien wrote: > From: Ethan Lien > > After we copied data to page cache in buffered I/O, we > 1. Insert a EXTENT_UPTODATE state into inode's io_tree, by > endio_readpage_release_extent(), set_extent_delalloc() or > set_extent_defrag(). > 2. Set page uptodate before we unlock the page. > > But the only place we check io_tree's EXTENT_UPTODATE state is in > btrfs_do_readpage(). We know we enter btrfs_do_readpage() only when we > have a non-uptodate page, so it is unnecessary to set EXTENT_UPTODATE. > > For example, when performing a buffered random read: > > fio --rw=randread --ioengine=libaio --direct=0 --numjobs=4 \ > --filesize=32G --size=4G --bs=4k --name=job \ > --filename=/mnt/file --name=job > > Then check how many extent_state in io_tree: > > cat /proc/slabinfo | grep btrfs_extent_state | awk '{print $2}' > > w/o this patch, we got 640567 btrfs_extent_state. > w/ this patch, we got 204 btrfs_extent_state. > > Maintaining such a big tree brings overhead since every I/O needs to insert > EXTENT_LOCKED, insert EXTENT_UPTODATE, then remove EXTENT_LOCKED. And in > every insert or remove, we need to lock io_tree, do tree search, alloc or > dealloc extent states. By removing unnecessary EXTENT_UPTODATE, we keep > io_tree in a minimal size and reduce overhead when performing buffered I/O. > > Signed-off-by: Ethan Lien > Reviewed-by: Robbie Ko > --- > > V2: Remove set_extent_uptodate() from btrfs_get_extent(), and when we found > a inline extent, set page uptodate in btrfs_do_readpage(). Added to misc-next, thanks.