Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753263AbbBMVUQ (ORCPT ); Fri, 13 Feb 2015 16:20:16 -0500 Received: from mail-ig0-f169.google.com ([209.85.213.169]:57159 "EHLO mail-ig0-f169.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752378AbbBMVUM (ORCPT ); Fri, 13 Feb 2015 16:20:12 -0500 Date: Fri, 13 Feb 2015 13:20:10 -0800 (PST) From: David Rientjes X-X-Sender: rientjes@chino.kir.corp.google.com To: Christoph Lameter cc: Joonsoo Kim , akpm@linuxfoundation.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, penberg@kernel.org, iamjoonsoo@lge.com, Jesper Dangaard Brouer Subject: Re: [PATCH 1/3] Slab infrastructure for array operations In-Reply-To: Message-ID: References: <20150210194804.288708936@linux.com> <20150210194811.787556326@linux.com> <20150213023534.GA6592@js1304-P5Q-DELUXE> User-Agent: Alpine 2.10 (DEB 1266 2009-07-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1896 Lines: 34 On Fri, 13 Feb 2015, Christoph Lameter wrote: > > I also think that this implementation is slub-specific. For example, > > in slab case, it is always better to access local cpu cache first than > > page allocator since slab doesn't use list to manage free objects and > > there is no cache line overhead like as slub. I think that, > > in kmem_cache_alloc_array(), just call to allocator-defined > > __kmem_cache_alloc_array() is better approach. > > What do you mean by "better"? Please be specific as to where you would see > a difference. And slab definititely manages free objects although > differently than slub. SLAB manages per cpu (local) objects, per node > partial lists etc. Same as SLUB. The cache line overhead is there but no > that big a difference in terms of choosing objects to get first. > I think because we currently lack a non-fallback implementation for slab that it may be premature to discuss what would be unified if such an implementation were to exist. That unification can always happen later if/when the slab implementation is proposed, but I don't think we should be unifying an implementation that doesn't exist. In other words, I think it would be much cleaner to do just define the generic array alloc and array free functions in mm/slab_common.c along with their EXPORT_SYMBOL()'s as simple callbacks to per-allocator __kmem_cache_{alloc,free}_array() implementations. I think it's also better from a source code perspective to avoid reading two different functions and then realizing that nothing is actually unified between them (and the absence of an unnecessary #ifdef is currently helpful). -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/