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 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id ABCD0ECAAD3 for ; Wed, 14 Sep 2022 22:51:46 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 41E996B0071; Wed, 14 Sep 2022 18:51:46 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 3CD9E6B0073; Wed, 14 Sep 2022 18:51:46 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 2944A8D0001; Wed, 14 Sep 2022 18:51:46 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0013.hostedemail.com [216.40.44.13]) by kanga.kvack.org (Postfix) with ESMTP id 165406B0071 for ; Wed, 14 Sep 2022 18:51:46 -0400 (EDT) Received: from smtpin07.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay01.hostedemail.com (Postfix) with ESMTP id DF4331C5B88 for ; Wed, 14 Sep 2022 22:51:45 +0000 (UTC) X-FDA: 79912189770.07.7CB4087 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by imf15.hostedemail.com (Postfix) with ESMTP id 97065A00AD for ; Wed, 14 Sep 2022 22:51:44 +0000 (UTC) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id ABFBF61F46; Wed, 14 Sep 2022 22:51:43 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id F09A7C433C1; Wed, 14 Sep 2022 22:51:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1663195903; bh=wJhU+7BFoQR8B41LdXid8aho7nAH+Au1OFPhdMiF+IQ=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=1fGFwzB+QZmC43IuwyQHTJ7LV9Hm8QZVDFIHX+IIyYDHoI3rD8mAintXcfZ2iPpTO TSneBTeL8XVVxmNpsVQ1Wpkjsa5CudvPSYe86yvZoiLAWENX+WrsCVxkYp0aBtzyR0 GoYnA71YUw6dMeqb2FsbtD5ogjGcQhAfVczGqBDg= Date: Wed, 14 Sep 2022 15:51:42 -0700 From: Andrew Morton To: Hongchen Zhang Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm/vmscan: don't scan adjust too much if current is not kswapd Message-Id: <20220914155142.bf388515a39fb45bae987231@linux-foundation.org> In-Reply-To: <20220914023318.549118-1-zhanghongchen@loongson.cn> References: <20220914023318.549118-1-zhanghongchen@loongson.cn> X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.33; x86_64-redhat-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1663195904; a=rsa-sha256; cv=none; b=gWve6oe07dcu8wJ4BXWYsPdjI1HrG+2uedYI2Mh5BNfYAh9sTYSfg8xa5YOSrqpAtUr68z 5Uwomt7l8Hy507SOt4BaNRgDR8SKukWE6R0S8Vj5/71CD+Jb48KV9K5aECVJUevvejYfFk Icv0kruErjRCyHeYcjipRpL1k+R0/lY= ARC-Authentication-Results: i=1; imf15.hostedemail.com; dkim=pass header.d=linux-foundation.org header.s=korg header.b=1fGFwzB+; dmarc=none; spf=pass (imf15.hostedemail.com: domain of akpm@linux-foundation.org designates 139.178.84.217 as permitted sender) smtp.mailfrom=akpm@linux-foundation.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1663195904; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=HpXLY3vS8emIo13dn5uxQ0H0PkyVZinZe3f/4Bvjkpw=; b=lYL9ntA8xVf9LOaB7pPQOhlRf5pNl/hylAlZZZ7TD8YJm3teBN5ZUrXQ+O1u7VjH1DixvL yQao1D/ay4PI9S8JzhMFgLqz4TTpw/UZWF708s6UBj8fq8lzpKzybvPptSbdxPrQtJIgCz QLN4cKuB4W66Bnr4mJh0qNm1kr89YT8= X-Rspam-User: Authentication-Results: imf15.hostedemail.com; dkim=pass header.d=linux-foundation.org header.s=korg header.b=1fGFwzB+; dmarc=none; spf=pass (imf15.hostedemail.com: domain of akpm@linux-foundation.org designates 139.178.84.217 as permitted sender) smtp.mailfrom=akpm@linux-foundation.org X-Rspamd-Server: rspam11 X-Stat-Signature: 1ckzwiawuoc7ifw4fwc1n1sepmnzxx7e X-Rspamd-Queue-Id: 97065A00AD X-HE-Tag: 1663195904-267831 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed, 14 Sep 2022 10:33:18 +0800 Hongchen Zhang wrote: > when a process falls into page fault and there is not enough free > memory,it will do direct reclaim. At the same time,it is holding > mmap_lock.So in case of multi-thread,it should exit from page fault > ASAP. > When reclaim memory,we do scan adjust between anon and file lru which > may cost too much time and trigger hung task for other thread.So for a > process which is not kswapd,it should just do a little scan adjust. Well, that's a pretty nasty bug. Before diving into a possible fix, can you please tell us more about how this happens? What sort of machine, what sort of workload. Can you suggest why others are not experiencing this? > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -3042,11 +3042,17 @@ static void shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc) > nr[lru] = targets[lru] * (100 - percentage) / 100; > nr[lru] -= min(nr[lru], nr_scanned); > > + if (!current_is_kswapd()) > + nr[lru] = min(nr[lru], nr_to_reclaim); > + > lru += LRU_ACTIVE; > nr_scanned = targets[lru] - nr[lru]; > nr[lru] = targets[lru] * (100 - percentage) / 100; > nr[lru] -= min(nr[lru], nr_scanned); > > + if (!current_is_kswapd()) > + nr[lru] = min(nr[lru], nr_to_reclaim); > + > scan_adjusted = true; > } > blk_finish_plug(&plug); It would be better if these additions had code comments explaining why they're there. But let's more fully understand the problem before altering your patch.