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 38524ECE58C for ; Mon, 7 Oct 2019 17:36:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 19B1220684 for ; Mon, 7 Oct 2019 17:36:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728814AbfJGRgt (ORCPT ); Mon, 7 Oct 2019 13:36:49 -0400 Received: from Galois.linutronix.de ([193.142.43.55]:45105 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728371AbfJGRgs (ORCPT ); Mon, 7 Oct 2019 13:36:48 -0400 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 Sender: linux-rt-users-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-rt-users@vger.kernel.org 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