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=-0.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS autolearn=no 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 9DECDC433E0 for ; Wed, 20 May 2020 01:40:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6C3C92075F for ; Wed, 20 May 2020 01:40:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1589938812; bh=vzjx/GG0epcegWe9y4yfSLiBocv5o0cqoYzvBOLTx1Q=; h=Date:From:To:Cc:Subject:In-Reply-To:References:List-ID:From; b=aBl1FAQ4g5HfXSPy75Se+gjwzJMllbu9St6PRUClmYL/kPzV+6A8XIZlpNbZ3ra9f 7rGrLAsPwMDlYIxw4k4T1jItPQh2me979/53xCTLp/CS2kjaeYLDV4fgxzj9M2bKuZ 6ur+ReiMJwLA1Iqf9cky2ksdGBq2vUr0f256RUrM= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728433AbgETBkL (ORCPT ); Tue, 19 May 2020 21:40:11 -0400 Received: from mail.kernel.org ([198.145.29.99]:39592 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726348AbgETBkL (ORCPT ); Tue, 19 May 2020 21:40:11 -0400 Received: from localhost.localdomain (c-73-231-172-41.hsd1.ca.comcast.net [73.231.172.41]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 9F92F2075F; Wed, 20 May 2020 01:40:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1589938810; bh=vzjx/GG0epcegWe9y4yfSLiBocv5o0cqoYzvBOLTx1Q=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=K747CHeFDoQ4W6ne6KtAIviU1ur/mXBOwXYIj67Beeb6VcYIGSJbqNyFo6RPBoWux +zD3dxY0hQSCoCY/S/mooBdd7DMgA975xp2rq0sR1Swxfbjd/a5hte7WcWt/icTWdW mMUK5ON9SvdfRaHhCarZy333oXuqiF2tVn+qQxEw= Date: Tue, 19 May 2020 18:40:10 -0700 From: Andrew Morton To: Charan Teja Reddy Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, vinmenon@codeaurora.org Subject: Re: [PATCH] mm, page_alloc: skip ->waternark_boost for atomic order-0 allocations Message-Id: <20200519184010.e77d25d7f6b853414e760d76@linux-foundation.org> In-Reply-To: <1589882284-21010-1-git-send-email-charante@codeaurora.org> References: <1589882284-21010-1-git-send-email-charante@codeaurora.org> X-Mailer: Sylpheed 3.5.1 (GTK+ 2.24.31; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 19 May 2020 15:28:04 +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. > > 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. Seems sensible. > --- 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. Nice comment, but I don't understand it ;) Why would testing gfp_mask prevent us from waking kswapd? > + */ > + if (unlikely(!order && !(alloc_flags & ALLOC_WMARK_MASK) && > + (alloc_flags & (ALLOC_HARDER | ALLOC_HIGH)))) { > + mark = zone->_watermark[WMARK_MIN]; > + } Why is this not implemented for higher-order allocation attempts? > if (!zone_watermark_fast(zone, order, mark, > ac->highest_zoneidx, alloc_flags)) { > int ret;