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=-8.1 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham 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 DA6C9C433E0 for ; Fri, 12 Jun 2020 11:07:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A5FEE207D8 for ; Fri, 12 Jun 2020 11:07:31 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=mg.codeaurora.org header.i=@mg.codeaurora.org header.b="Rqi0/V5P" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726289AbgFLLHa (ORCPT ); Fri, 12 Jun 2020 07:07:30 -0400 Received: from mail27.static.mailgun.info ([104.130.122.27]:38600 "EHLO mail27.static.mailgun.info" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725868AbgFLLH3 (ORCPT ); Fri, 12 Jun 2020 07:07:29 -0400 DKIM-Signature: a=rsa-sha256; v=1; c=relaxed/relaxed; d=mg.codeaurora.org; q=dns/txt; s=smtp; t=1591960049; h=Content-Transfer-Encoding: Content-Type: In-Reply-To: MIME-Version: Date: Message-ID: From: References: Cc: To: Subject: Sender; bh=BnCXV1eT4PYNxgO3yiQdkkkdhOl00dNU0VRujVxajZ8=; b=Rqi0/V5Pn+cYI4AwSShmVwzbob7MsP38PWPRuX/3wI8UW4lLFsKjwvlfgM076o55yBaDP32z 7JXtG9Srelwcjy3uok2fIiCaAVNRVwXCWwRUmkDgDwArtjJ9iXaWnDOUxRrPNA9o/H7KJNP1 t8NISpLLYV6J7JDzEz+2stoiX00= X-Mailgun-Sending-Ip: 104.130.122.27 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-n03.prod.us-west-2.postgun.com with SMTP id 5ee361efad153efa342b57df (version=TLS1.2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256); Fri, 12 Jun 2020 11:07:27 GMT Received: by smtp.codeaurora.org (Postfix, from userid 1001) id BB888C433C8; Fri, 12 Jun 2020 11:07:27 +0000 (UTC) Received: from [192.168.1.102] (unknown [183.83.143.239]) (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 6870DC433CA; Fri, 12 Jun 2020 11:07:25 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 smtp.codeaurora.org 6870DC433CA 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=none smtp.mailfrom=charante@codeaurora.org Subject: Re: [PATCH] mm, page_alloc: skip ->waternark_boost for atomic order-0 allocations To: Mel Gorman Cc: akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, vinmenon@codeaurora.org References: <1589882284-21010-1-git-send-email-charante@codeaurora.org> <20200609122811.GK3127@techsingularity.net> From: Charan Teja Kalla Message-ID: <8a94eccb-5d57-7168-9c6a-03241407630d@codeaurora.org> Date: Fri, 12 Jun 2020 16:37:22 +0530 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.9.0 MIME-Version: 1.0 In-Reply-To: <20200609122811.GK3127@techsingularity.net> Content-Type: text/plain; charset=iso-8859-15 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Thanks Mel for feedback. On 6/9/2020 5:58 PM, Mel Gorman wrote: > On Tue, May 19, 2020 at 03:28:04PM +0530, Charan Teja Reddy wrote: >> When boosting is enabled, it is observed that rate of atomic order-0 >> allocation failures are high due to the fact that free levels in the >> system are checked with ->watermark_boost offset. This is not a problem >> for sleepable allocations but for atomic allocations which looks like >> regression. >> > > Are high-order allocations in general of interest to this platform? If > not then a potential option is to simply disable boosting. The patch is > still relevant but it's worth thinking about. > Yes we do care till order-3. >> This problem is seen frequently on system setup of Android kernel >> running on Snapdragon hardware with 4GB RAM size. When no extfrag event >> occurred in the system, ->watermark_boost factor is zero, thus the >> watermark configurations in the system are: >> _watermark = ( >> [WMARK_MIN] = 1272, --> ~5MB >> [WMARK_LOW] = 9067, --> ~36MB >> [WMARK_HIGH] = 9385), --> ~38MB >> watermark_boost = 0 >> >> After launching some memory hungry applications in Android which can >> cause extfrag events in the system to an extent that ->watermark_boost >> can be set to max i.e. default boost factor makes it to 150% of high >> watermark. >> _watermark = ( >> [WMARK_MIN] = 1272, --> ~5MB >> [WMARK_LOW] = 9067, --> ~36MB >> [WMARK_HIGH] = 9385), --> ~38MB >> watermark_boost = 14077, -->~57MB >> >> With default system configuration, for an atomic order-0 allocation to >> succeed, having free memory of ~2MB will suffice. But boosting makes >> the min_wmark to ~61MB thus for an atomic order-0 allocation to be >> successful system should have minimum of ~23MB of free memory(from >> calculations of zone_watermark_ok(), min = 3/4(min/2)). But failures are >> observed despite system is having ~20MB of free memory. In the testing, >> this is reproducible as early as first 300secs since boot and with >> furtherlowram configurations(<2GB) it is observed as early as first >> 150secs since boot. >> >> These failures can be avoided by excluding the ->watermark_boost in >> watermark caluculations for atomic order-0 allocations. >> >> Signed-off-by: Charan Teja Reddy >> --- >> mm/page_alloc.c | 12 ++++++++++++ >> 1 file changed, 12 insertions(+) >> >> diff --git a/mm/page_alloc.c b/mm/page_alloc.c >> index d001d61..5193d7e 100644 >> --- a/mm/page_alloc.c >> +++ b/mm/page_alloc.c >> @@ -3709,6 +3709,18 @@ static bool zone_allows_reclaim(struct zone *local_zone, struct zone *zone) >> } >> >> mark = wmark_pages(zone, alloc_flags & ALLOC_WMARK_MASK); >> + /* >> + * Allow GFP_ATOMIC order-0 allocations to exclude the >> + * zone->watermark_boost in its watermark calculations. >> + * We rely on the ALLOC_ flags set for GFP_ATOMIC >> + * requests in gfp_to_alloc_flags() for this. Reason not to >> + * use the GFP_ATOMIC directly is that we want to fall back >> + * to slow path thus wake up kswapd. >> + */ > > The comment is a bit difficult to parse. Maybe this. > > /* > * Ignore watermark boosting for GFP_ATOMIC order-0 allocations > * when checking the min watermark. The min watermark is the > * point where boosting is ignored so that kswapd is woken up > * when below the low watermark. > */ > > I left out the ALLOC_ part for reasons that are explained blow. > >> + if (unlikely(!order && !(alloc_flags & ALLOC_WMARK_MASK) && >> + (alloc_flags & (ALLOC_HARDER | ALLOC_HIGH)))) { >> + mark = zone->_watermark[WMARK_MIN]; >> + } > > The second check is a bit more obscure than it needs to be and depends > on WMARK_MIN == 0. That will probably be true forever but it's not > obvious at a glance. I suggest something like > ((alloc_flags & ALLOC_WMARK_MASK) == WMARK_MIN). > > For detecting atomic alloctions, you rely on the either ALLOC_HARDER or > ALLOC_HIGH being set. ALLOC_HIGH can be set for non-atomic allocations > and ALLOC_HARDER can be set for RT tasks. You probably should just test > the gfp_mask because as it stands non-atomic allocations can ignore the > boost too. > > Finally, the patch puts an unlikely check into a relatively fast path even > though watermarks may be fine with or without boosting. Instead you could > put the checks in zone_watermark_fast() if and only if the watermarks > failed the first time. If the checks pass, the watermarks get checked > a second time. This will be fractionally slower for requests failing > watermark checks but there is no penalty for most allocation requests. > It would need the gfp_mask to be passed into zone_watermark_fast but > as it's an inlined function, there should be no cost to passing in the > arguement i.e. do something like this at the end of zone_watermark_fast > > if (__zone_watermark_ok(z, order, mark, classzone_idx, alloc_flags, free_pages)) > return true; > > /* Ignore watermark boosting for .... */ > if (unlikely(!order .....) { > mark = ... > return __zone_watermark_ok(...); > } > > return false; > Incorporated these suggestions at: https://lore.kernel.org/patchwork/patch/1254998/. Can you please help in reviewing? -- The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project