From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f52.google.com (mail-pa0-f52.google.com [209.85.220.52]) by kanga.kvack.org (Postfix) with ESMTP id 127596B0032 for ; Tue, 9 Jun 2015 22:15:03 -0400 (EDT) Received: by padev16 with SMTP id ev16so24575528pad.0 for ; Tue, 09 Jun 2015 19:15:02 -0700 (PDT) Received: from mail.linuxfoundation.org (mail.linuxfoundation.org. [140.211.169.12]) by mx.google.com with ESMTPS id kg4si11339937pad.60.2015.06.09.19.15.02 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 09 Jun 2015 19:15:02 -0700 (PDT) Date: Tue, 9 Jun 2015 19:17:55 -0700 From: Andrew Morton Subject: Re: [RFC][PATCH 0/5] do not dereference NULL pools in pools' destroy() functions Message-Id: <20150609191755.867a36c3.akpm@linux-foundation.org> In-Reply-To: References: <1433851493-23685-1-git-send-email-sergey.senozhatsky@gmail.com> <20150609142523.b717dba6033ee08de997c8be@linux-foundation.org> <20150609185150.8c9fed8d.akpm@linux-foundation.org> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Christoph Lameter Cc: Sergey Senozhatsky , Minchan Kim , Pekka Enberg , Joonsoo Kim , Michal Hocko , David Rientjes , linux-mm@kvack.org, linux-kernel@vger.kernel.org, sergey.senozhatsky.work@gmail.com, Joe Perches On Tue, 9 Jun 2015 21:00:58 -0500 (CDT) Christoph Lameter wrote: > On Tue, 9 Jun 2015, Andrew Morton wrote: > > > > Why do this at all? > > > > For the third time: because there are approx 200 callsites which are > > already doing it. > > Did some grepping and I did see some call sites that do this but the > majority has to do other processing as well. > > 200 call sites? Do we have that many uses of caches? Typical prod system > have ~190 caches active and the merging brings that down to half of that. I didn't try terribly hard. z:/usr/src/linux-4.1-rc7> grep -r -C1 kmem_cache_destroy . | grep "if [(]" | wc -l 158 It's a lot, anyway. > > More than half of the kmem_cache_destroy() callsites are declining that > > value by open-coding the NULL test. That's reality and we should recognize > > it. > > Well that may just indicate that we need to have a look at those > callsites and the reason there to use a special cache at all. This makes no sense. Go look at the code. drivers/staging/lustre/lustre/llite/super25.c, for example. It's all in the basic unwind/recover/exit code. > If the cache > is just something that kmalloc can provide then why create a special > cache. On the other hand if something special needs to be accomplished > then it would make sense to have special processing on kmem_cache_destroy. This has nothing to do with anything. We're talking about a basic "if I created this cache then destroy it" operation. It's a common pattern. mm/ exists to serve client code and as a lot of client code is doing this, we should move it into mm/ so as to serve client code better. -- 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