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=-15.4 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,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 EE3F5C433E0 for ; Mon, 18 Jan 2021 12:48:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A4BAF22286 for ; Mon, 18 Jan 2021 12:48:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2404242AbhARMr2 (ORCPT ); Mon, 18 Jan 2021 07:47:28 -0500 Received: from m43-15.mailgun.net ([69.72.43.15]:42467 "EHLO m43-15.mailgun.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2404169AbhARMl4 (ORCPT ); Mon, 18 Jan 2021 07:41:56 -0500 DKIM-Signature: a=rsa-sha256; v=1; c=relaxed/relaxed; d=mg.codeaurora.org; q=dns/txt; s=smtp; t=1610973695; h=Content-Transfer-Encoding: Content-Type: In-Reply-To: MIME-Version: Date: Message-ID: From: References: Cc: To: Subject: Sender; bh=/kzjP1LLFmNE/nZIymawoQ3MxnPFmkzXlNyMYW+x4iM=; b=hxsQQtuNjtqYMGqP1+jztVUvKlm2g6X2GjBtsx74/sek1OHfDlTdS0Hj2l2BTzjUvLhkgd99 Gz4coyOLPifTstbB3Wd6h5cSap4D3d58dSj7RncD8S41Zwy4B60r29eU1UkFJjkjUIH5Rxtw f5A3YPpTPKsg/3+e9JhfRtAiroA= X-Mailgun-Sending-Ip: 69.72.43.15 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-n10.prod.us-east-1.postgun.com with SMTP id 600581e5e23dedcc3a13ca8b (version=TLS1.2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256); Mon, 18 Jan 2021 12:41:09 GMT Sender: charante=codeaurora.org@mg.codeaurora.org Received: by smtp.codeaurora.org (Postfix, from userid 1001) id 7852FC43468; Mon, 18 Jan 2021 12:41:08 +0000 (UTC) Received: from [192.168.29.110] (unknown [49.37.151.66]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) (Authenticated sender: charante) by smtp.codeaurora.org (Postfix) with ESMTPSA id 62231C433C6; Mon, 18 Jan 2021 12:41:04 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 smtp.codeaurora.org 62231C433C6 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=charante@codeaurora.org Subject: Re: [PATCH V2] mm/compaction: correct deferral logic for proactive compaction To: Vlastimil Babka , akpm@linux-foundation.org, mhocko@suse.com, khalid.aziz@oracle.com, ngupta@nitingupta.dev, vinmenon@codeaurora.org Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <1610972408-20986-1-git-send-email-charante@codeaurora.org> <777bf9c5-82db-041b-55ee-6868ab78ef70@suse.cz> From: Charan Teja Kalla Message-ID: <4548a0d8-0cf7-08d1-795d-914e3948d134@codeaurora.org> Date: Mon, 18 Jan 2021 18:11:01 +0530 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.6.1 MIME-Version: 1.0 In-Reply-To: <777bf9c5-82db-041b-55ee-6868ab78ef70@suse.cz> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Thanks Vlasitmil!! On 1/18/2021 6:07 PM, Vlastimil Babka wrote: > On 1/18/21 1:20 PM, Charan Teja Reddy wrote: >> should_proactive_compact_node() returns true when sum of the >> weighted fragmentation score of all the zones in the node is greater >> than the wmark_high of compaction, which then triggers the proactive >> compaction that operates on the individual zones of the node. But >> proactive compaction runs on the zone only when its weighted >> fragmentation score is greater than wmark_low(=wmark_high - 10). >> >> This means that the sum of the weighted fragmentation scores of all the >> zones can exceed the wmark_high but individual weighted fragmentation >> zone scores can still be less than wmark_low which makes the unnecessary >> trigger of the proactive compaction only to return doing nothing. >> >> Issue with the return of proactive compaction with out even trying is >> its deferral. It is simply deferred for 1 << COMPACT_MAX_DEFER_SHIFT if >> the scores across the proactive compaction is same, thinking that >> compaction didn't make any progress but in reality it didn't even try. >> With the delay between successive retries for proactive compaction is >> 500msec, it can result into the deferral for ~30sec with out even trying >> the proactive compaction. >> >> Test scenario is that: compaction_proactiveness=50 thus the wmark_low = >> 50 and wmark_high = 60. System have 2 zones(Normal and Movable) with >> sizes 5GB and 6GB respectively. After opening some apps on the android, >> the weighted fragmentation scores of these zones are 47 and 49 >> respectively. Since the sum of these fragmentation scores are above the >> wmark_high which triggers the proactive compaction and there since the >> individual zones weighted fragmentation scores are below wmark_low, it >> returns without trying the proactive compaction. As a result the >> weighted fragmentation scores of the zones are still 47 and 49 which >> makes the existing logic to defer the compaction thinking that >> noprogress is made across the compaction. >> >> Fix this by checking just zone fragmentation score, not the weighted, in >> __compact_finished() and use the zones weighted fragmentation score in >> fragmentation_score_node(). In the test case above, If the weighted >> average of is above wmark_high, then individual score (not adjusted) of >> atleast one zone has to be above wmark_high. Thus it avoids the >> unnecessary trigger and deferrals of the proactive compaction. >> >> Fix-suggested-by: Vlastimil Babka >> Signed-off-by: Charan Teja Reddy > > Acked-by: Vlastimil Babka > > But I would move fragmentation_score_zone() above > fragmentation_score_zone_weighted(), so fragmentation_score_zone_weighted() can > call fragmentation_score_zone() instead of having two places with > extfrag_for_order(...). Yes, this suggestion makes the code cleaner. I will raise V3 for this. Thanks. > > Thanks. > >> --- >> >> Changes in V2: Addressed comments from vlastimil >> >> Changes in V1: https://lore.kernel.org/patchwork/patch/1364646/ >> >> mm/compaction.c | 19 ++++++++++++++----- >> 1 file changed, 14 insertions(+), 5 deletions(-) >> >> diff --git a/mm/compaction.c b/mm/compaction.c >> index e5acb97..1b98427 100644 >> --- a/mm/compaction.c >> +++ b/mm/compaction.c >> @@ -1924,16 +1924,16 @@ static bool kswapd_is_running(pg_data_t *pgdat) >> } >> >> /* >> - * A zone's fragmentation score is the external fragmentation wrt to the >> - * COMPACTION_HPAGE_ORDER scaled by the zone's size. It returns a value >> - * in the range [0, 100]. >> + * A weighted zone's fragmentation score is the external fragmentation >> + * wrt to the COMPACTION_HPAGE_ORDER scaled by the zone's size. It >> + * returns a value in the range [0, 100]. >> * >> * The scaling factor ensures that proactive compaction focuses on larger >> * zones like ZONE_NORMAL, rather than smaller, specialized zones like >> * ZONE_DMA32. For smaller zones, the score value remains close to zero, >> * and thus never exceeds the high threshold for proactive compaction. >> */ >> -static unsigned int fragmentation_score_zone(struct zone *zone) >> +static unsigned int fragmentation_score_zone_weighted(struct zone *zone) >> { >> unsigned long score; >> >> @@ -1943,6 +1943,15 @@ static unsigned int fragmentation_score_zone(struct zone *zone) >> } >> >> /* >> + * A zone's fragmentation score is the external fragmentation wrt to the >> + * COMPACTION_HPAGE_ORDER. It returns a value in the range [0, 100]. >> + */ >> +static unsigned int fragmentation_score_zone(struct zone *zone) >> +{ >> + return extfrag_for_order(zone, COMPACTION_HPAGE_ORDER); >> +} >> + >> +/* >> * The per-node proactive (background) compaction process is started by its >> * corresponding kcompactd thread when the node's fragmentation score >> * exceeds the high threshold. The compaction process remains active till >> @@ -1958,7 +1967,7 @@ static unsigned int fragmentation_score_node(pg_data_t *pgdat) >> struct zone *zone; >> >> zone = &pgdat->node_zones[zoneid]; >> - score += fragmentation_score_zone(zone); >> + score += fragmentation_score_zone_weighted(zone); >> } >> >> return score; >> > -- The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project