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 X-Spam-Level: X-Spam-Status: No, score=-20.2 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id EFD1EC433DB for ; Tue, 16 Mar 2021 09:35:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id AC4996500E for ; Tue, 16 Mar 2021 09:35:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232577AbhCPJeq (ORCPT ); Tue, 16 Mar 2021 05:34:46 -0400 Received: from m42-2.mailgun.net ([69.72.42.2]:37344 "EHLO m42-2.mailgun.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229618AbhCPJeO (ORCPT ); Tue, 16 Mar 2021 05:34:14 -0400 DKIM-Signature: a=rsa-sha256; v=1; c=relaxed/relaxed; d=mg.codeaurora.org; q=dns/txt; s=smtp; t=1615887254; h=In-Reply-To: Content-Type: MIME-Version: References: Message-ID: Subject: Cc: To: From: Date: Sender; bh=9UfEyw436vIESU6W/ayoumRpdy+NziJpgKqhqz2zc6A=; b=Y6Ivj6jLSjXj0WBXqENsr58EZVyn+jJAbBx7SlbydNQbGPOf/EZdy0HnxFCE8CRcLAWgVRk9 8Mchk0T9Ko4VklxXC/KVJw0XQpyq/tdHGy0IGPzrpe9h81hHPIqzPvt/TXvQOdoPbN6BIiug 1xAbHk0sumP3smusVTJX2HNS48U= X-Mailgun-Sending-Ip: 69.72.42.2 X-Mailgun-Sid: WyI0MWYwYSIsICJsaW51eC1rZXJuZWxAdmdlci5rZXJuZWwub3JnIiwgImJlOWU0YSJd Received: from smtp.codeaurora.org (ec2-35-166-182-171.us-west-2.compute.amazonaws.com [35.166.182.171]) by smtp-out-n04.prod.us-west-2.postgun.com with SMTP id 60507b943f267701a41fad34 (version=TLS1.2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256); Tue, 16 Mar 2021 09:34:12 GMT Sender: stummala=codeaurora.org@mg.codeaurora.org Received: by smtp.codeaurora.org (Postfix, from userid 1001) id 1F8E4C433CA; Tue, 16 Mar 2021 09:34:12 +0000 (UTC) Received: from codeaurora.org (unknown [202.46.22.19]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) (Authenticated sender: stummala) by smtp.codeaurora.org (Postfix) with ESMTPSA id 35FC2C433CA; Tue, 16 Mar 2021 09:34:08 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 smtp.codeaurora.org 35FC2C433CA Authentication-Results: aws-us-west-2-caf-mail-1.web.codeaurora.org; dmarc=none (p=none dis=none) header.from=codeaurora.org Authentication-Results: aws-us-west-2-caf-mail-1.web.codeaurora.org; spf=fail smtp.mailfrom=stummala@codeaurora.org Date: Tue, 16 Mar 2021 15:04:06 +0530 From: Sahitya Tummala To: Chao Yu Cc: Jaegeuk Kim , linux-f2fs-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org, stummala@codeaurora.org Subject: Re: [PATCH] f2fs: fix the discard thread sleep timeout under high utilization Message-ID: <20210316093406.GC8562@codeaurora.org> References: <1615784186-2693-1-git-send-email-stummala@codeaurora.org> <49be0c70-4fe4-6acd-b508-08621f0623c0@huawei.com> <20210315074645.GA8562@codeaurora.org> <0c7220d7-416e-32b7-96cb-effd3f84d6e2@huawei.com> <20210315094502.GB8562@codeaurora.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.24 (2015-08-30) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Chao, Thanks for the review and suggestions. I think the below code should work and cover all the cases we discussed. Let me test it and then put up a new patchset for review. Thanks, Sahitya. Mon, Mar 15, 2021 at 06:31:00PM +0800, Chao Yu wrote: > Hi Sahitya, > > On 2021/3/15 17:45, Sahitya Tummala wrote: > >Hi Chao, > > > >On Mon, Mar 15, 2021 at 04:10:22PM +0800, Chao Yu wrote: > >>Hi Sahitya, > >> > >>On 2021/3/15 15:46, Sahitya Tummala wrote: > >>>Hi Chao, > >>> > >>>On Mon, Mar 15, 2021 at 02:12:44PM +0800, Chao Yu wrote: > >>>>Sahitya, > >>>> > >>>>On 2021/3/15 12:56, Sahitya Tummala wrote: > >>>>>When f2fs is heavily utilized over 80%, the current discard policy > >>>>>sets the max sleep timeout of discard thread as 50ms > >>>>>(DEF_MIN_DISCARD_ISSUE_TIME). But this is set even when there are > >>>>>no pending discard commands to be issued. This results into > >>>>>unnecessary frequent and periodic wake ups of the discard thread. > >>>>>This patch adds check for pending discard commands in addition > >>>>>to heavy utilization condition to prevent those wake ups. > >>>> > >>>>Could this commit fix your issue? > >>>> > >>>>https://git.kernel.org/pub/scm/linux/kernel/git/jaegeuk/f2fs.git/commit/?h=dev&id=43f8c47ea7d59c7b2270835f1d7c4618a1ea27b6 > >>>> > >>>I don't think it will help because we are changing the max timeout of the > >>>dpolicy itself in __init_discard_policy() when util > 80% as below - > >>> > >>>dpolicy->max_interval = DEF_MIN_DISCARD_ISSUE_TIME; > >>> > >>>And issue_discard_thread() uses this value as wait_ms, when there > >>>are no more pending discard commands to be issued. > >>> > >>> } else { > >>> wait_ms = dpolicy.max_interval; > >>> } > >>> > >>> > >>>The new patch posted above is not changing anything related to the max_interval. > >>>Hence, I think it won't help the uncessary wakeup problem I am trying to solve > >>>for this condition - util > 80% and when there are no pending discards. > >>> > >>>Please let me know if i am missing something. > >> > >>Copied, thanks for the explanation. > >> > >>But there is another case which can cause this issue in the case of > >>disk util < 80%. > >> > >>wait_ms = DEF_MIN_DISCARD_ISSUE_TIME; > >> > >>do { > >> wait_event_interruptible_timeout(, wait_ms); > >> > >> ... > >> > >> if (!atomic_read(&dcc->discard_cmd_cnt)) > >>[1] new statement > >> continue; > >> > >>} while(); > >> > >>Then the loop will wakeup whenever 50ms timeout. > >> > >Yes, only for a short period of time i.e., until the first discard command > >is issued. Once a discard is issued, it will use > >wait_ms = dpolicy.max_interval; > > > >>So, to avoid this case, shouldn't we reset wait_ms to dpolicy.max_interval > >>at [1]? > >> > >Yes, we can add that to cover the above case. > > > >>Meanwhile, how about relocating discard_cmd_cnt check after > >>__init_discard_policy(DPOLICY_FORCE)? and olny set .max_interval to > >>DEF_MAX_DISCARD_ISSUE_TIME if there is no discard command, and keep > >>.granularity to 1? > >> > > > >There is not need to change .granularity, right? It will be controlled > > I think so. > > >as per utilization as it is done today. Only max_interval and wait_ms > >needs to be updated. Does this look good? > > > >diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c > >index d7076796..958ad1e 100644 > >--- a/fs/f2fs/segment.c > >+++ b/fs/f2fs/segment.c > >@@ -1772,13 +1772,16 @@ static int issue_discard_thread(void *data) > > wait_ms = dpolicy.max_interval; > > continue; > > } > >- if (!atomic_read(&dcc->discard_cmd_cnt)) > >- continue; > >- > > if (sbi->gc_mode == GC_URGENT_HIGH || > > !f2fs_available_free_memory(sbi, DISCARD_CACHE)) > > __init_discard_policy(sbi, &dpolicy, DPOLICY_FORCE, 1); > > > >+ if (!atomic_read(&dcc->discard_cmd_cnt)) { > >+ dpolicy.max_interval = DEF_MAX_DISCARD_ISSUE_TIME; > >+ wait_ms = dpolicy.max_interval; > >+ continue; > >+ } > > Hmm.. how about cleaning up to configure discard policy in > __init_discard_policy()? > > Something like: > > --- > fs/f2fs/segment.c | 19 ++++++++++++------- > 1 file changed, 12 insertions(+), 7 deletions(-) > > diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c > index 592927ccffa7..684463a70eb9 100644 > --- a/fs/f2fs/segment.c > +++ b/fs/f2fs/segment.c > @@ -1118,7 +1118,9 @@ static void __init_discard_policy(struct f2fs_sb_info *sbi, > dpolicy->ordered = true; > if (utilization(sbi) > DEF_DISCARD_URGENT_UTIL) { > dpolicy->granularity = 1; > - dpolicy->max_interval = DEF_MIN_DISCARD_ISSUE_TIME; > + if (atomic_read(&SM_I(sbi)->dcc_info->discard_cmd_cnt)) > + dpolicy->max_interval = > + DEF_MIN_DISCARD_ISSUE_TIME; > } > } else if (discard_type == DPOLICY_FORCE) { > dpolicy->min_interval = DEF_MIN_DISCARD_ISSUE_TIME; > @@ -1734,8 +1736,15 @@ static int issue_discard_thread(void *data) > set_freezable(); > > do { > - __init_discard_policy(sbi, &dpolicy, DPOLICY_BG, > - dcc->discard_granularity); > + if (sbi->gc_mode == GC_URGENT_HIGH || > + !f2fs_available_free_memory(sbi, DISCARD_CACHE)) > + __init_discard_policy(sbi, &dpolicy, DPOLICY_FORCE, 1); > + else > + __init_discard_policy(sbi, &dpolicy, DPOLICY_BG, > + dcc->discard_granularity); > + > + if (!atomic_read(&dcc->discard_cmd_cnt)) > + wait_ms = dpolicy.max_interval; > > wait_event_interruptible_timeout(*q, > kthread_should_stop() || freezing(current) || > @@ -1762,10 +1771,6 @@ static int issue_discard_thread(void *data) > if (!atomic_read(&dcc->discard_cmd_cnt)) > continue; > > - if (sbi->gc_mode == GC_URGENT_HIGH || > - !f2fs_available_free_memory(sbi, DISCARD_CACHE)) > - __init_discard_policy(sbi, &dpolicy, DPOLICY_FORCE, 1); > - > sb_start_intwrite(sbi->sb); > > issued = __issue_discard_cmd(sbi, &dpolicy); > -- > 2.29.2 > > Thoughts? > > Thanks, > > >+ > > sb_start_intwrite(sbi->sb); > > > > issued = __issue_discard_cmd(sbi, &dpolicy); > > > >thanks, > >Sahitya. > > > >>Thanks, > >> > >>> > >>>Thanks, > >>>Sahitya. > >>> > >>>>Thanks, > >>>> > >>>>> > >>>>>Signed-off-by: Sahitya Tummala > >>>>>--- > >>>>> fs/f2fs/segment.c | 5 ++++- > >>>>> 1 file changed, 4 insertions(+), 1 deletion(-) > >>>>> > >>>>>diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c > >>>>>index dced46c..df30220 100644 > >>>>>--- a/fs/f2fs/segment.c > >>>>>+++ b/fs/f2fs/segment.c > >>>>>@@ -1112,6 +1112,8 @@ static void __init_discard_policy(struct f2fs_sb_info *sbi, > >>>>> struct discard_policy *dpolicy, > >>>>> int discard_type, unsigned int granularity) > >>>>> { > >>>>>+ struct discard_cmd_control *dcc = SM_I(sbi)->dcc_info; > >>>>>+ > >>>>> /* common policy */ > >>>>> dpolicy->type = discard_type; > >>>>> dpolicy->sync = true; > >>>>>@@ -1129,7 +1131,8 @@ static void __init_discard_policy(struct f2fs_sb_info *sbi, > >>>>> dpolicy->io_aware = true; > >>>>> dpolicy->sync = false; > >>>>> dpolicy->ordered = true; > >>>>>- if (utilization(sbi) > DEF_DISCARD_URGENT_UTIL) { > >>>>>+ if (utilization(sbi) > DEF_DISCARD_URGENT_UTIL && > >>>>>+ atomic_read(&dcc->discard_cmd_cnt)) { > >>>>> dpolicy->granularity = 1; > >>>>> dpolicy->max_interval = DEF_MIN_DISCARD_ISSUE_TIME; > >>>>> } > >>>>> > >>> > > -- -- Sent by a consultant of the Qualcomm Innovation Center, Inc. The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum.