From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pd0-f171.google.com (mail-pd0-f171.google.com [209.85.192.171]) by kanga.kvack.org (Postfix) with ESMTP id D28D26B0035 for ; Thu, 29 May 2014 16:05:46 -0400 (EDT) Received: by mail-pd0-f171.google.com with SMTP id y13so109600pdi.30 for ; Thu, 29 May 2014 13:05:46 -0700 (PDT) Received: from mail.linuxfoundation.org (mail.linuxfoundation.org. [140.211.169.12]) by mx.google.com with ESMTP id xl4si2412900pab.5.2014.05.29.13.05.45 for ; Thu, 29 May 2014 13:05:45 -0700 (PDT) Date: Thu, 29 May 2014 13:05:44 -0700 From: Andrew Morton Subject: Re: [PATCH] vmalloc: use rcu list iterator to reduce vmap_area_lock contention Message-Id: <20140529130544.56213f048f331723329ff828@linux-foundation.org> In-Reply-To: <1401344554-3596-1-git-send-email-iamjoonsoo.kim@lge.com> References: <1401344554-3596-1-git-send-email-iamjoonsoo.kim@lge.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Joonsoo Kim Cc: Zhang Yanfei , Johannes Weiner , Andi Kleen , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Richard Yao On Thu, 29 May 2014 15:22:34 +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. The mixture of rcu protection and spinlock protection for vmap_area_list is pretty confusing. Are you able to describe the overall design here? When and why do we use one versus the other? -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org