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=-5.9 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS, T_DKIMWL_WL_HIGH,URIBL_BLOCKED,USER_AGENT_GIT 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 05E90C04A6B for ; Mon, 6 May 2019 14:44:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id CE30D20449 for ; Mon, 6 May 2019 14:44:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1557153866; bh=R0OHY4dDdSHj3imxbYEZ9us7NW27oCdlDlgR1jrtXm4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=Y1QgsN68pv/gXfhLTs8ObDHyaFcQ0Zq5aQP73jX6YXrbAai034NBaN0bPgI0ogQIY /2VNdVbdOK45bqY/20rL/spuOeMaK/OlDDiP0BnE08aQPss/340PdQOGLz+ohGSivx R2d2Iet9BXGW5g35AhQhy2KNqHcTE+Xf8VdS4fck= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728788AbfEFOoZ (ORCPT ); Mon, 6 May 2019 10:44:25 -0400 Received: from mail.kernel.org ([198.145.29.99]:40618 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727259AbfEFOoX (ORCPT ); Mon, 6 May 2019 10:44:23 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (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 AB11721019; Mon, 6 May 2019 14:44:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1557153863; bh=R0OHY4dDdSHj3imxbYEZ9us7NW27oCdlDlgR1jrtXm4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=z+JK/ZYJRDR4GR6Ohj/Y8bvZtNLOLtWI7e0/viRlbtfOeJSTflWjep+DbkU2vgZBL ZBKNa6Pd8Un0gCS9Qg/MHhzM0YGjqUT4BBpNJDVATO5y+373PVJ/qWRCNdo2PUJwVk ge1se20w5isIa8AO3+pf6CMaPGUQRsqyM9GD2AKE= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Minchan Kim , Shakeel Butt , Johannes Weiner , Michal Hocko , Tetsuo Handa , Anshuman Khandual , Andrew Morton , Linus Torvalds , Robert Kolchmeyer Subject: [PATCH 4.14 24/75] mm: do not stall register_shrinker() Date: Mon, 6 May 2019 16:32:32 +0200 Message-Id: <20190506143055.350550574@linuxfoundation.org> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20190506143053.287515952@linuxfoundation.org> References: <20190506143053.287515952@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Minchan Kim commit e496612c5130567fc9d5f1969ca4b86665aa3cbb upstream. Shakeel Butt reported he has observed in production systems that the job loader gets stuck for 10s of seconds while doing a mount operation. It turns out that it was stuck in register_shrinker() because some unrelated job was under memory pressure and was spending time in shrink_slab(). Machines have a lot of shrinkers registered and jobs under memory pressure have to traverse all of those memcg-aware shrinkers and affect unrelated jobs which want to register their own shrinkers. To solve the issue, this patch simply bails out slab shrinking if it is found that someone wants to register a shrinker in parallel. A downside is it could cause unfair shrinking between shrinkers. However, it should be rare and we can add compilcated logic if we find it's not enough. [akpm@linux-foundation.org: tweak code comment] Link: http://lkml.kernel.org/r/20171115005602.GB23810@bbox Link: http://lkml.kernel.org/r/1511481899-20335-1-git-send-email-minchan@kernel.org Signed-off-by: Minchan Kim Signed-off-by: Shakeel Butt Reported-by: Shakeel Butt Tested-by: Shakeel Butt Acked-by: Johannes Weiner Acked-by: Michal Hocko Cc: Tetsuo Handa Cc: Anshuman Khandual Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds [rkolchmeyer: Backported to 4.14: adjusted context] Signed-off-by: Robert Kolchmeyer Signed-off-by: Greg Kroah-Hartman --- mm/vmscan.c | 9 +++++++++ 1 file changed, 9 insertions(+) --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -502,6 +502,15 @@ static unsigned long shrink_slab(gfp_t g sc.nid = 0; freed += do_shrink_slab(&sc, shrinker, nr_scanned, nr_eligible); + /* + * Bail out if someone want to register a new shrinker to + * prevent the regsitration from being stalled for long periods + * by parallel ongoing shrinking. + */ + if (rwsem_is_contended(&shrinker_rwsem)) { + freed = freed ? : 1; + break; + } } up_read(&shrinker_rwsem);