From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx197.postini.com [74.125.245.197]) by kanga.kvack.org (Postfix) with SMTP id 1F5356B002B for ; Wed, 17 Oct 2012 17:05:58 -0400 (EDT) Received: by mail-ob0-f169.google.com with SMTP id va7so9563669obc.14 for ; Wed, 17 Oct 2012 14:05:57 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: References: <20121008150949.GA15130@redhat.com> <20121017040515.GA13505@redhat.com> <507E4531.1070700@jp.fujitsu.com> From: KOSAKI Motohiro Date: Wed, 17 Oct 2012 17:05:37 -0400 Message-ID: Subject: Re: [patch for-3.7] mm, mempolicy: fix printing stack contents in numa_maps Content-Type: text/plain; charset=ISO-8859-1 Sender: owner-linux-mm@kvack.org List-ID: To: David Rientjes Cc: Kamezawa Hiroyuki , Dave Jones , Andrew Morton , Linus Torvalds , bhutchings@solarflare.com, Konstantin Khlebnikov , Naoya Horiguchi , Hugh Dickins , linux-kernel@vger.kernel.org, linux-mm@kvack.org On Wed, Oct 17, 2012 at 3:50 PM, David Rientjes wrote: > On Wed, 17 Oct 2012, KOSAKI Motohiro wrote: > >> > I think this refcounting is better than using task_lock(). >> >> I don't think so. get_vma_policy() is used from fast path. In other >> words, number of >> atomic ops is sensible for allocation performance. > > There are enhancements that we can make with refcounting: for instance, we > may want to avoid doing it in the super-fast path when the policy is > default_policy and then just do > > if (mpol != &default_policy) > mpol_put(mpol); > >> Instead, I'd like >> to use spinlock >> for shared mempolicy instead of mutex. >> > > Um, this was just changed to a mutex last week in commit b22d127a39dd > ("mempolicy: fix a race in shared_policy_replace()") so that sp_alloc() > can be done with GFP_KERNEL, so I didn't consider reverting that behavior. > Are you nacking that patch, which you acked, now? Yes, sadly. /proc usage is a corner case issue. It's not worth to strike main path. see commit 52cd3b0740 and around patches. That explain why we avoided your approach. -- 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