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 lists.sourceforge.net (lists.sourceforge.net [216.105.38.7]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 8D861C41513 for ; Mon, 7 Aug 2023 19:55:39 +0000 (UTC) Received: from [127.0.0.1] (helo=sfs-ml-4.v29.lw.sourceforge.com) by sfs-ml-4.v29.lw.sourceforge.com with esmtp (Exim 4.95) (envelope-from ) id 1qT6KI-0001eD-LP; Mon, 07 Aug 2023 19:55:39 +0000 Received: from [172.30.20.202] (helo=mx.sourceforge.net) by sfs-ml-4.v29.lw.sourceforge.com with esmtps (TLS1.2) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.95) (envelope-from ) id 1qT6KI-0001e6-7W for linux-f2fs-devel@lists.sourceforge.net; Mon, 07 Aug 2023 19:55:38 +0000 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=sourceforge.net; s=x; h=In-Reply-To:Content-Type:MIME-Version:References: Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To:Content-Transfer-Encoding: Content-ID:Content-Description:Resent-Date:Resent-From:Resent-Sender: Resent-To:Resent-Cc:Resent-Message-ID:List-Id:List-Help:List-Unsubscribe: List-Subscribe:List-Post:List-Owner:List-Archive; bh=oxztR1ogNrO5RhL4WxSpAg4ZNdqODdLcJDXGGVQrn58=; b=mIb5mxxLykyEGNIaZ8BjDvi0xZ UizDXNNGd1+hF9T2Bsh5ZgfY+5hf5h5i0LuTUuDVzQ+YVKhT9Xhz56Fcr1bS/O7j7+HrcHsqnWQoT OSsGNQ0WWXISJB7ZZ91cK0KnBmCUvGkG2bDcaJ43HrxamaDHhINL9vSOv0yV0sHQOoZM=; DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=sf.net; s=x ; h=In-Reply-To:Content-Type:MIME-Version:References:Message-ID:Subject:Cc:To :From:Date:Sender:Reply-To:Content-Transfer-Encoding:Content-ID: Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc :Resent-Message-ID:List-Id:List-Help:List-Unsubscribe:List-Subscribe: List-Post:List-Owner:List-Archive; bh=oxztR1ogNrO5RhL4WxSpAg4ZNdqODdLcJDXGGVQrn58=; b=II+EhQmJmQWDlmt0B4+dfinVi6 tCQN8M7GGwQH2xLHumnz75cIkRisfhxCVe+7rI2fOA4cnG3T3Lk6kYnU4cvTn61vJbOi/fGoeKiMe mvmjWBn7RQ7OdYWXkLFkiOMC1IsNBjMSo58xJLuX9TYUZJgCcmDwLZ7my6msQSNot5mE=; Received: from dfw.source.kernel.org ([139.178.84.217]) by sfi-mx-2.v28.lw.sourceforge.com with esmtps (TLS1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.95) id 1qT6KH-00030x-DK for linux-f2fs-devel@lists.sourceforge.net; Mon, 07 Aug 2023 19:55:38 +0000 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id AB6D9621BC; Mon, 7 Aug 2023 19:55:31 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id F16EFC433C8; Mon, 7 Aug 2023 19:55:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1691438131; bh=B7bvlj514nf25uE0E4eqZHoMG7i/L04k6cyUl8PvZ24=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=t+lJXacWUiobGozvqdrEAMYiOMt8R4+yBBZqy6SWXHdTeqrHM6WAPMzkCsF+Zw1iR GhIULEGMS/NZV7dDG+ySn2m6PG4Ug/lhIfzDDp76er1dIodjsgrPyxKfGBQhIoFnY8 5Fzsjzp2yQzvxTEslzqqi0A0FtGsWFPDMtZ5sq+5AfNaBrL5RXtyweezGgLzY4BBTO LE54naW/GD3fv9WHwUG9ZlSCQK/I69H3WHUeQiEPlEo/XzJKiSw9eBSarKIdKlEgDe UKLcZlyHzvBtOtdsAnoam/4DiqNjLvXCxooNBavd5tlohXpnLEg7Y+1DaLJHSBrm13 Oco9qHi/srrBA== Date: Mon, 7 Aug 2023 12:55:29 -0700 From: Jaegeuk Kim To: Chao Yu Message-ID: References: <330c96f7-fbad-dd17-6368-f1378b3b5375@kernel.org> <87acf602-1587-0615-909d-6e60c66c3cda@kernel.org> <5e5f830b-1b13-4893-fbb0-4c7e99ec9f32@kernel.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: X-Headers-End: 1qT6KH-00030x-DK Subject: Re: [f2fs-dev] [PATCH v2] f2fs: do not issue small discard commands during checkpoint X-BeenThere: linux-f2fs-devel@lists.sourceforge.net X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-kernel@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: linux-f2fs-devel-bounces@lists.sourceforge.net On 08/07, Chao Yu wrote: > On 2023/8/5 4:52, Jaegeuk Kim wrote: > > On 07/25, Chao Yu wrote: > > > On 2023/7/22 4:23, Jaegeuk Kim wrote: > > > > On 07/13, Chao Yu wrote: > > > > > On 2023/7/12 23:55, Jaegeuk Kim wrote: > > > > > > On 07/12, Chao Yu wrote: > > > > > > > On 2023/7/12 0:37, Jaegeuk Kim wrote: > > > > > > > > On 07/06, Chao Yu wrote: > > > > > > > > > On 2023/7/6 1:30, Jaegeuk Kim wrote: > > > > > > > > > > On 07/04, Chao Yu wrote: > > > > > > > > > > > On 2023/7/4 18:53, Jaegeuk Kim wrote: > > > > > > > > > > > > On 07/03, Chao Yu wrote: > > > > > > > > > > > > > On 2023/6/15 0:10, Jaegeuk Kim wrote: > > > > > > > > > > > > > > If there're huge # of small discards, this will increase checkpoint latency > > > > > > > > > > > > > > insanely. Let's issue small discards only by trim. > > > > > > > > > > > > > > > > > > > > > > > > > > > > Signed-off-by: Jaegeuk Kim > > > > > > > > > > > > > > --- > > > > > > > > > > > > > > > > > > > > > > > > > > > > Change log from v1: > > > > > > > > > > > > > > - move the skip logic to avoid dangling objects > > > > > > > > > > > > > > > > > > > > > > > > > > > > fs/f2fs/segment.c | 2 +- > > > > > > > > > > > > > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > > > > > > > > > > > > > > > > > > > > > > > > > diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c > > > > > > > > > > > > > > index 8c7af8b4fc47..0457d620011f 100644 > > > > > > > > > > > > > > --- a/fs/f2fs/segment.c > > > > > > > > > > > > > > +++ b/fs/f2fs/segment.c > > > > > > > > > > > > > > @@ -2193,7 +2193,7 @@ void f2fs_clear_prefree_segments(struct f2fs_sb_info *sbi, > > > > > > > > > > > > > > len = next_pos - cur_pos; > > > > > > > > > > > > > > if (f2fs_sb_has_blkzoned(sbi) || > > > > > > > > > > > > > > - (force && len < cpc->trim_minlen)) > > > > > > > > > > > > > > + !force || len < cpc->trim_minlen) > > > > > > > > > > > > > > goto skip; > > > > > > > > > > > > > > > > > > > > > > > > > > Sorry for late reply. > > > > > > > > > > > > > > > > > > > > > > > > > > We have a configuration for such case, what do you think of setting > > > > > > > > > > > > > max_small_discards to zero? otherwise, w/ above change, max_small_discards > > > > > > > > > > > > > logic may be broken? > > > > > > > > > > > > > > > > > > > > > > > > > > What: /sys/fs/f2fs//max_small_discards > > > > > > > > > > > > > Date: November 2013 > > > > > > > > > > > > > Contact: "Jaegeuk Kim" > > > > > > > > > > > > > Description: Controls the issue rate of discard commands that consist of small > > > > > > > > > > > > > blocks less than 2MB. The candidates to be discarded are cached until > > > > > > > > > > > > > checkpoint is triggered, and issued during the checkpoint. > > > > > > > > > > > > > By default, it is disabled with 0. > > > > > > > > > > > > > > > > > > > > > > > > > > Or, if we prefer to disable small_discards by default, what about below change: > > > > > > > > > > > > > > > > > > > > > > > > I think small_discards is fine, but need to avoid long checkpoint latency only. > > > > > > > > > > > > > > > > > > > > > > I didn't get you, do you mean we can still issue small discard by > > > > > > > > > > > fstrim, so small_discards functionality is fine? > > > > > > > > > > > > > > > > > > > > You got the point. > > > > > > > > > > > > > > > > > > Well, actually, what I mean is max_small_discards sysfs entry's functionality > > > > > > > > > is broken. Now, the entry can not be used to control number of small discards > > > > > > > > > committed by checkpoint. > > > > > > > > > > > > > > > > Could you descrbie this problem first? > > > > > > > > > > > > > > Oh, alright, actually, I've described this problem literally, but maybe it's not > > > > > > > clear, let me give some examples as below: > > > > > > > > > > > > > > echo 0 > /sys/fs/f2fs/vdb/max_small_discards > > > > > > > xfs_io -f /mnt/f2fs/file -c "pwrite 0 2m" -c "fsync" > > > > > > > xfs_io /mnt/f2fs/file -c "fpunch 0 4k" > > > > > > > sync > > > > > > > cat /proc/fs/f2fs/vdb/discard_plist_info |head -2 > > > > > > > > > > > > > > echo 100 > /sys/fs/f2fs/vdb/max_small_discards > > > > > > > rm /mnt/f2fs/file > > > > > > > xfs_io -f /mnt/f2fs/file -c "pwrite 0 2m" -c "fsync" > > > > > > > xfs_io /mnt/f2fs/file -c "fpunch 0 4k" > > > > > > > sync > > > > > > > cat /proc/fs/f2fs/vdb/discard_plist_info |head -2 > > > > > > > > > > > > > > Before the patch: > > > > > > > > > > > > > > Discard pend list(Show diacrd_cmd count on each entry, .:not exist): > > > > > > > 0 . . . . . . . . > > > > > > > > > > > > > > Discard pend list(Show diacrd_cmd count on each entry, .:not exist): > > > > > > > 0 3 1 . . . . . . > > > > > > > > > > > > > > After the patch: > > > > > > > Discard pend list(Show diacrd_cmd count on each entry, .:not exist): > > > > > > > 0 . . . . . . . . > > > > > > > > > > > > > > Discard pend list(Show diacrd_cmd count on each entry, .:not exist): > > > > > > > 0 . . . . . . . . > > > > > > > > > > > > > > So, now max_small_discards can not be used to control small discard number > > > > > > > cached by checkpoint. > > > > > > > > > > Let me explain more: > > > > > > > > > > Previously, we have two mechanisms to cache & submit small discards: > > > > > > > > > > a) set max small discard number in /sys/fs/f2fs/vdb/max_small_discards, and checkpoint > > > > > will cache small discard candidates w/ configured maximum number. > > > > > > > > > > b) call FITRIM ioctl, also, checkpoint in f2fs_trim_fs() will cache small discard > > > > > candidates w/ configured discard granularity, but w/o limitation of number. FSTRIM > > > > > interface is asynchronized, so it won't submit discard directly. > > > > > > > > > > Finally, discard thread will submit them in background periodically. > > > > > > > > > > So what I mean is the mechanism a) is broken, since no matter how we configure the > > > > > sysfs entry /sys/fs/f2fs/vdb/max_small_discards, checkpoint will not cache small > > > > > discard candidates any more. > > > > > > > > Ok, it seems what I encountered before was adding this small discard even > > > > after issuing it by checkpoint. Thoughts? > > > > > > Do you mean: in f2fs_clear_prefree_segments(), small discard may overlap > > > segment granularity discard? > > > > I didn't dig enough tho, don't think so. Somehow I got a loop as below which > > said the same LBA was issued and added back repeatedly, not seen this short log > > unfortunately. > > > > > > > > e.g. > > > - f2fs_clear_prefree_segments > > > - f2fs_issue_discard(0, 512) --- segment granularity discard > > > - f2fs_issue_discard(0, 1) --- small discard > > > - f2fs_issue_discard(5, 1) --- small discard > > > > > > Thanks, > > [snip] > > > > > f2fs_discard-25-752 [003] ..... 9744.173111: f2fs_issue_discard: dev = (254,51), blkstart = 0x18c0ca, blklen = 0x1 > > > > f2fs_discard-25-752 [004] ..... 9744.175348: f2fs_remove_discard: dev = (254,51), blkstart = 0x18c0ca, blklen = 0x1 > > I don't see any loop via above log, am I missing something? > > The traces were printed in below call paths, and it printed the same LBAs as > expected? I said the log was cut to show the loop enoughly. I'll try to reproduce this later locally. > > - issue_discard_thread > - __issue_discard_cmd > - __submit_discard_cmd > - trace_f2fs_issue_discard > 9744.173111: f2fs_issue_discard: dev = (254,51), blkstart = 0x18c0ca, blklen = 0x1 > - __wait_all_discard_cmd > - __wait_discard_cmd_range > - __remove_discard_cmd > - trace_f2fs_remove_discard > 9744.175348: f2fs_remove_discard: dev = (254,51), blkstart = 0x18c0ca, blklen = 0x1 > > Thanks, > > > > > > > > > > > > > > > So, it needs to fix max_small_discards sysfs functionality? or just drop the > > > > > functionality? > > > > > > > > > > > > > > > > > Since we do not submit small discards anymore during checkpoint. Why not relying > > > > > > on the discard thread to issue them? > > > > > > > > > > Sorry, I'm not sure I get your point, do you mean max_small_discards functionality > > > > > is obsoleted, so it recommended to use fstrim to cache & submit small discards? > > > > > > > > > > Let me know, if I'm missing something or misunderstanding the point. > > > > > > > > > > Thanks, > > > > > > > > > > > > > > > > > > > > > > > > > Thanks, > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > I think there is another way to achieve "avoid long checkpoint latency caused > > > > > > > > > by committing huge # of small discards", the way is we can set max_small_discards > > > > > > > > > to small value or zero, w/ such configuration, it will take checkpoint much less > > > > > > > > > time or no time to committing small discard due to below control logic: > > > > > > > > > > > > > > > > > > f2fs_flush_sit_entries() > > > > > > > > > { > > > > > > > > > ... > > > > > > > > > if (!(cpc->reason & CP_DISCARD)) { > > > > > > > > > cpc->trim_start = segno; > > > > > > > > > add_discard_addrs(sbi, cpc, false); > > > > > > > > > } > > > > > > > > > ... > > > > > > > > > } > > > > > > > > > > > > > > > > > > add_discard_addrs() > > > > > > > > > { > > > > > > > > > ... > > > > > > > > > while (force || SM_I(sbi)->dcc_info->nr_discards <= > > > > > > > > > SM_I(sbi)->dcc_info->max_discards) { > > > > > > > > > > > > > > > > > > It will break the loop once nr_discards is larger than max_discards, if > > > > > > > > > max_discards is set to zero, checkpoint won't take time to handle small discards. > > > > > > > > > > > > > > > > > > ... > > > > > > > > > if (!de) { > > > > > > > > > de = f2fs_kmem_cache_alloc(discard_entry_slab, > > > > > > > > > GFP_F2FS_ZERO, true, NULL); > > > > > > > > > de->start_blkaddr = START_BLOCK(sbi, cpc->trim_start); > > > > > > > > > list_add_tail(&de->list, head); > > > > > > > > > } > > > > > > > > > ... > > > > > > > > > } > > > > > > > > > ... > > > > > > > > > > > > > > > > > > Thanks, > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > Thanks, > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > From eb89d9b56e817e3046d7fa17165b12416f09d456 Mon Sep 17 00:00:00 2001 > > > > > > > > > > > > > From: Chao Yu > > > > > > > > > > > > > Date: Mon, 3 Jul 2023 09:06:53 +0800 > > > > > > > > > > > > > Subject: [PATCH] Revert "f2fs: enable small discard by default" > > > > > > > > > > > > > > > > > > > > > > > > > > This reverts commit d618ebaf0aa83d175658aea5291e0c459d471d39 in order > > > > > > > > > > > > > to disable small discard by default, so that if there're huge number of > > > > > > > > > > > > > small discards, it will decrease checkpoint's latency obviously. > > > > > > > > > > > > > > > > > > > > > > > > > > Also, this patch reverts 9ac00e7cef10 ("f2fs: do not issue small discard > > > > > > > > > > > > > commands during checkpoint"), due to it breaks small discard feature which > > > > > > > > > > > > > may be configured via sysfs entry max_small_discards. > > > > > > > > > > > > > > > > > > > > > > > > > > Fixes: 9ac00e7cef10 ("f2fs: do not issue small discard commands during checkpoint") > > > > > > > > > > > > > Signed-off-by: Chao Yu > > > > > > > > > > > > > --- > > > > > > > > > > > > > fs/f2fs/segment.c | 4 ++-- > > > > > > > > > > > > > 1 file changed, 2 insertions(+), 2 deletions(-) > > > > > > > > > > > > > > > > > > > > > > > > > > diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c > > > > > > > > > > > > > index 14c822e5c9c9..0a313368f18b 100644 > > > > > > > > > > > > > --- a/fs/f2fs/segment.c > > > > > > > > > > > > > +++ b/fs/f2fs/segment.c > > > > > > > > > > > > > @@ -2193,7 +2193,7 @@ void f2fs_clear_prefree_segments(struct f2fs_sb_info *sbi, > > > > > > > > > > > > > len = next_pos - cur_pos; > > > > > > > > > > > > > > > > > > > > > > > > > > if (f2fs_sb_has_blkzoned(sbi) || > > > > > > > > > > > > > - !force || len < cpc->trim_minlen) > > > > > > > > > > > > > + (force && len < cpc->trim_minlen)) > > > > > > > > > > > > > goto skip; > > > > > > > > > > > > > > > > > > > > > > > > > > f2fs_issue_discard(sbi, entry->start_blkaddr + cur_pos, > > > > > > > > > > > > > @@ -2269,7 +2269,7 @@ static int create_discard_cmd_control(struct f2fs_sb_info *sbi) > > > > > > > > > > > > > atomic_set(&dcc->queued_discard, 0); > > > > > > > > > > > > > atomic_set(&dcc->discard_cmd_cnt, 0); > > > > > > > > > > > > > dcc->nr_discards = 0; > > > > > > > > > > > > > - dcc->max_discards = MAIN_SEGS(sbi) << sbi->log_blocks_per_seg; > > > > > > > > > > > > > + dcc->max_discards = 0; > > > > > > > > > > > > > dcc->max_discard_request = DEF_MAX_DISCARD_REQUEST; > > > > > > > > > > > > > dcc->min_discard_issue_time = DEF_MIN_DISCARD_ISSUE_TIME; > > > > > > > > > > > > > dcc->mid_discard_issue_time = DEF_MID_DISCARD_ISSUE_TIME; > > > > > > > > > > > > > -- > > > > > > > > > > > > > 2.40.1 > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > f2fs_issue_discard(sbi, entry->start_blkaddr + cur_pos, _______________________________________________ Linux-f2fs-devel mailing list Linux-f2fs-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel