From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757362AbaE2M4K (ORCPT ); Thu, 29 May 2014 08:56:10 -0400 Received: from mail-pb0-f47.google.com ([209.85.160.47]:42611 "EHLO mail-pb0-f47.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756275AbaE2M4I (ORCPT ); Thu, 29 May 2014 08:56:08 -0400 Message-ID: <1401368165.3645.21.camel@edumazet-glaptop2.roam.corp.google.com> Subject: Re: [PATCH] vmalloc: use rcu list iterator to reduce vmap_area_lock contention From: Eric Dumazet To: Joonsoo Kim Cc: Andrew Morton , Zhang Yanfei , Johannes Weiner , Andi Kleen , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Richard Yao Date: Thu, 29 May 2014 05:56:05 -0700 In-Reply-To: <1401344554-3596-1-git-send-email-iamjoonsoo.kim@lge.com> References: <1401344554-3596-1-git-send-email-iamjoonsoo.kim@lge.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.2.3-0ubuntu6 Content-Transfer-Encoding: 7bit Mime-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 2014-05-29 at 15:22 +0900, Joonsoo Kim wrote: > Richard Yao reported a month ago that his system have a trouble > with vmap_area_lock contention during performance analysis > by /proc/meminfo. Andrew asked why his analysis checks /proc/meminfo > stressfully, but he didn't answer it. > > https://lkml.org/lkml/2014/4/10/416 > > Although I'm not sure that this is right usage or not, there is a solution > reducing vmap_area_lock contention with no side-effect. That is just > to use rcu list iterator in get_vmalloc_info(). This function only needs > values on vmap_area structure, so we don't need to grab a spinlock. > > Reported-by: Richard Yao > Signed-off-by: Joonsoo Kim Nice, I was considering the same Acked-by: Eric Dumazet