From mboxrd@z Thu Jan 1 00:00:00 1970 Subject: Re: [PATCH 08/29] mm: kmem_cache_objs_to_pages() From: Peter Zijlstra In-Reply-To: <84144f020702210747t50d7d92ei1a2f5da8bf117d40@mail.gmail.com> References: <20070221144304.512721000@taijtu.programming.kicks-ass.net> <20070221144842.299190000@taijtu.programming.kicks-ass.net> <84144f020702210747t50d7d92ei1a2f5da8bf117d40@mail.gmail.com> Content-Type: text/plain Date: Thu, 22 Feb 2007 10:28:28 +0100 Message-Id: <1172136508.6374.41.camel@twins> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Pekka Enberg Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, netdev@vger.kernel.org, Trond Myklebust , Thomas Graf , David Miller List-ID: On Wed, 2007-02-21 at 17:47 +0200, Pekka Enberg wrote: > Hi Peter, > > On 2/21/07, Peter Zijlstra wrote: > > Provide a method to calculate the number of pages needed to store a given > > number of slab objects (upper bound when considering possible partial and > > free slabs). > > So how does this work? You ask the slab allocator how many pages you > need for a given number of objects and then those pages are available > to it via the page allocator? Can other users also dip into those > reserves? Everybody (ab)using PF_MEMALLOC or the new __GFP_EMERGENCY. > I would prefer we simply have an API for telling the slab allocator to > keep certain number of pages in a reserve for a cache rather than > exposing internals such as object size to rest of the world. Keeping the free pages in the page allocator is good for the buddy system. Although you could probably implement a reserve interface without actually claiming the pages. However, doing it like so separates the making of the reserve from the actual kmem_cache object, I can just carry a sum of pages around instead of a list of kmem_cache pointers. I calculate a potential reserve, I might never actually commit to making (and using) the reserve. Also, I don't see what internals are exposed, kmem_cache is still private to slab.c. -- 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