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 87CC3C433EF for ; Mon, 29 Nov 2021 08:39:40 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 050F46B0078; Mon, 29 Nov 2021 03:39:30 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 001796B007B; Mon, 29 Nov 2021 03:39:29 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id E0C206B007D; Mon, 29 Nov 2021 03:39:29 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0123.hostedemail.com [216.40.44.123]) by kanga.kvack.org (Postfix) with ESMTP id D30CF6B0078 for ; Mon, 29 Nov 2021 03:39:29 -0500 (EST) Received: from smtpin26.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id 97AC380EA467 for ; Mon, 29 Nov 2021 08:39:19 +0000 (UTC) X-FDA: 78861318480.26.027F7FC Received: from smtp-out1.suse.de (smtp-out1.suse.de [195.135.220.28]) by imf15.hostedemail.com (Postfix) with ESMTP id 728F8D00009A for ; Mon, 29 Nov 2021 08:39:12 +0000 (UTC) Received: from relay2.suse.de (relay2.suse.de [149.44.160.134]) by smtp-out1.suse.de (Postfix) with ESMTP id B6ECA212CB; Mon, 29 Nov 2021 08:39:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1638175157; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=y1/HRvQWe5bupilVHXWVZDusBm8nr9LZt0uqBedKdKA=; b=J4qijL9j7NKJC0s4vnqOlrDs2BSFPsMfOKHgq75fzXUbUMmG6kDFsHC446/t8l9HnhxQGi 1X48f8fJWJ9sQfbIUtxwtWBvay0Vz0aMdUE83pfyyc4cYhcZsz7fW82PhBT10czrrivQxi qE3pMx7MyDOyufnfhAhM+rP1LoUdXcM= Received: from suse.cz (unknown [10.100.201.86]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by relay2.suse.de (Postfix) with ESMTPS id 8242FA3B83; Mon, 29 Nov 2021 08:39:17 +0000 (UTC) Date: Mon, 29 Nov 2021 09:39:16 +0100 From: Michal Hocko To: Hao Lee Cc: Matthew Wilcox , Linux MM , Johannes Weiner , vdavydov.dev@gmail.com, Shakeel Butt , cgroups@vger.kernel.org, LKML Subject: Re: [PATCH] mm: reduce spinlock contention in release_pages() Message-ID: References: <20211125080238.GA7356@haolee.io> <20211125123133.GA7758@haolee.io> <20211126162623.GA10277@haolee.io> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20211126162623.GA10277@haolee.io> X-Rspamd-Queue-Id: 728F8D00009A X-Stat-Signature: omig5o8bq6kbsf5ki7rt8tfojaizgmhm Authentication-Results: imf15.hostedemail.com; dkim=pass header.d=suse.com header.s=susede1 header.b=J4qijL9j; dmarc=pass (policy=quarantine) header.from=suse.com; spf=pass (imf15.hostedemail.com: domain of mhocko@suse.com designates 195.135.220.28 as permitted sender) smtp.mailfrom=mhocko@suse.com X-Rspamd-Server: rspam02 X-HE-Tag: 1638175152-298058 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 Fri 26-11-21 16:26:23, Hao Lee wrote: [...] > I will try Matthew's idea to use semaphore or mutex to limit the number of BE > jobs that are in the exiting path. This sounds like a feasible approach for > our scenario... I am not really sure this is something that would be acceptable. Your problem is resource partitioning. Papering that over by a lock is not the right way to go. Besides that you will likely hit a hard question on how many tasks to allow to run concurrently. Whatever the value some workload will very likely going to suffer. We cannot assume admin to chose the right value because there is no clear answer for that. Not to mention other potential problems - e.g. even more priority inversions etc. -- Michal Hocko SUSE Labs