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 222A76B0068 for ; Fri, 28 Sep 2012 03:50:55 -0400 (EDT) Message-ID: <506555E9.2030809@parallels.com> Date: Fri, 28 Sep 2012 11:46:49 +0400 From: Glauber Costa MIME-Version: 1.0 Subject: Re: [PATCH] slab: Ignore internal flags in cache creation References: <1348571866-31738-1-git-send-email-glommer@parallels.com> <00000139fe408877-40bc98e3-322c-4ba2-be72-e298ff28e694-000000@email.amazonses.com> <5062C029.308@parallels.com> <5063F94C.4090600@parallels.com> In-Reply-To: Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: David Rientjes Cc: Christoph Lameter , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Michal Hocko , Pekka Enberg On 09/28/2012 02:56 AM, David Rientjes wrote: > On Thu, 27 Sep 2012, Glauber Costa wrote: > >> But I still don't see the big reason for your objection. If other >> allocator start using those bits, they would not be passed to >> kmem_cache_alloc anyway, right? So what would be the big problem in >> masking them out before it? >> > > A slab allocator implementation may allow for additional bits that are > currently not used or used for internal purposes by the current set of > slab allocators to be passed in the unsigned long to kmem_cache_create() > that would be a no-op on other allocators. It's implementation defined, > so this masking should be done in the implementation, i.e. > __kmem_cache_create(). > > For context, as many people who attended the kernel summit and LinuxCon > are aware, a new slab allocator is going to be proposed soon that actually > uses additional bits that aren't defined for all slab allocators. My > opinion is that leaving unused bits and reserved bits to the > implementation is the best software engineering practice. > I am happy as long as we don't BUG and can mask out that feature. If Christoph is happy with me masking it in the SLAB only, I'm also fine. -- 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