From mboxrd@z Thu Jan 1 00:00:00 1970 From: Peter Zijlstra Subject: Re: [PATCH 08/40] mm: kmem_cache_objsize Date: Fri, 04 May 2007 19:59:05 +0200 Message-ID: <1178301545.24217.56.camel@twins> References: <20070504102651.923946304@chello.nl> <20070504103157.215424767@chello.nl> Mime-Version: 1.0 Content-Type: text/plain Content-Transfer-Encoding: 7bit Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, netdev@vger.kernel.org, Trond Myklebust , Thomas Graf , David Miller , James Bottomley , Mike Christie , Andrew Morton , Daniel Phillips , Pekka Enberg To: Christoph Lameter Return-path: Received: from amsfep17-int.chello.nl ([213.46.243.15]:9225 "EHLO amsfep18-int.chello.nl" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1031451AbXEDR7J (ORCPT ); Fri, 4 May 2007 13:59:09 -0400 In-Reply-To: Sender: netdev-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On Fri, 2007-05-04 at 09:36 -0700, Christoph Lameter wrote: > On Fri, 4 May 2007, Peter Zijlstra wrote: > > > Expost buffer_size in order to allow fair estimates on the actual space > > used/needed. > > If its just an estimate that you are after then I think ksize is > sufficient. > > The buffer size does not include the other per slab overhead that SLAB > needs nor the alignment overhead or the padding. For SLUB you'd be more > lucky but there it does not include the per slab padding that exist. > > Need to check how this is going to be used. It is difficult to estimate > slab use because this depends on the availability of object slots in > partial slabs. > > I could add a function that tells you how many object you could allocate > from a slab without the page allocator becoming involved? It would count > the object slots available on the partial slabs. I need to know how many pages to reserve to allocate a given number of items from a given slab; assuming the partial slabs are empty. That is, I need a worst case upper bound.