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=-20.3 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, 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 3AA2FC433E6 for ; Mon, 15 Mar 2021 09:46:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 16E8964EE7 for ; Mon, 15 Mar 2021 09:46:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229756AbhCOJqD (ORCPT ); Mon, 15 Mar 2021 05:46:03 -0400 Received: from m42-2.mailgun.net ([69.72.42.2]:38134 "EHLO m42-2.mailgun.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229703AbhCOJpa (ORCPT ); Mon, 15 Mar 2021 05:45:30 -0400 DKIM-Signature: a=rsa-sha256; v=1; c=relaxed/relaxed; d=mg.codeaurora.org; q=dns/txt; s=smtp; t=1615801530; h=In-Reply-To: Content-Type: MIME-Version: References: Message-ID: Subject: Cc: To: From: Date: Sender; bh=YLGpfatS6jxFUxU0k6zFjnxWQ3M1naXEThx/ikE7O3g=; b=wHVh8kYmSXKWjucgU47B8Lud1vw7hlh8QsT4JadIvK7BzGxyuPcdp7t2lymcgEHs1QTb/p2C 9ABMZsRv6W/fEST2d18nxirayj8tm8TIUDqOMFVt2Y88SmmhOskh88chWRXTs9zgvOwWrPZF 1vhb0vrvwjlDFrMOLjL0zw+NZHc= 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-n02.prod.us-east-1.postgun.com with SMTP id 604f2ca5e3fca7d0a6bec1b1 (version=TLS1.2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256); Mon, 15 Mar 2021 09:45:09 GMT Sender: stummala=codeaurora.org@mg.codeaurora.org Received: by smtp.codeaurora.org (Postfix, from userid 1001) id AE025C43465; Mon, 15 Mar 2021 09:45:08 +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 C9F06C433CA; Mon, 15 Mar 2021 09:45:05 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 smtp.codeaurora.org C9F06C433CA 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: Mon, 15 Mar 2021 15:15:02 +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: <20210315094502.GB8562@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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <0c7220d7-416e-32b7-96cb-effd3f84d6e2@huawei.com> User-Agent: Mutt/1.5.24 (2015-08-30) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 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; + } + 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.