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=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 F0328ECE58C for ; Mon, 7 Oct 2019 17:36:49 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 9FEC220684 for ; Mon, 7 Oct 2019 17:36:49 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9FEC220684 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linutronix.de Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 39C5E8E0005; Mon, 7 Oct 2019 13:36:49 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 34C878E0003; Mon, 7 Oct 2019 13:36:49 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 261DA8E0005; Mon, 7 Oct 2019 13:36:49 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0218.hostedemail.com [216.40.44.218]) by kanga.kvack.org (Postfix) with ESMTP id 0641E8E0003 for ; Mon, 7 Oct 2019 13:36:48 -0400 (EDT) Received: from smtpin15.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with SMTP id 93D8C485A for ; Mon, 7 Oct 2019 17:36:48 +0000 (UTC) X-FDA: 76017693696.15.knife32_759941c0c0e4e X-HE-Tag: knife32_759941c0c0e4e X-Filterd-Recvd-Size: 2179 Received: from Galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) by imf34.hostedemail.com (Postfix) with ESMTP for ; Mon, 7 Oct 2019 17:36:48 +0000 (UTC) Received: from bigeasy by Galois.linutronix.de with local (Exim 4.80) (envelope-from ) id 1iHWw8-0001MQ-J4; Mon, 07 Oct 2019 19:36:44 +0200 Date: Mon, 7 Oct 2019 19:36:44 +0200 From: Sebastian Andrzej Siewior To: Uladzislau Rezki Cc: Daniel Wagner , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-rt-users@vger.kernel.org, Andrew Morton Subject: Re: [PATCH] mm: vmalloc: Use the vmap_area_lock to protect ne_fit_preload_node Message-ID: <20191007173644.hiiukrl2xryziro3@linutronix.de> References: <20191003090906.1261-1-dwagner@suse.de> <20191004153728.c5xppuqwqcwecbe6@linutronix.de> <20191004162041.GA30806@pc636> <20191004163042.jpiau6dlxqylbpfh@linutronix.de> <20191007083037.zu3n5gindvo7damg@beryllium.lan> <20191007105631.iau6zhxqjeuzajnt@linutronix.de> <20191007162330.GA26503@pc636> <20191007163443.6owts5jp2frum7cy@beryllium.lan> <20191007165611.GA26964@pc636> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20191007165611.GA26964@pc636> User-Agent: NeoMutt/20180716 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000001, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 2019-10-07 18:56:11 [+0200], Uladzislau Rezki wrote: > Actually there is a high lock contention on vmap_area_lock, because it > is still global. You can have a look at last slide: > > https://linuxplumbersconf.org/event/4/contributions/547/attachments/287/479/Reworking_of_KVA_allocator_in_Linux_kernel.pdf > > so this change will make it a bit higher. From the other hand i agree > that for rt it should be fixed, probably it could be done like: > > ifdef PREEMPT_RT > migrate_disable() > #else > preempt_disable() > ... > > but i am not sure it is good either. What is to be expected on average? Is the lock acquired and then released again because the slot is empty and memory needs to be allocated or can it be assumed that this hardly happens? Sebastian