Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932803AbXF2E2S (ORCPT ); Fri, 29 Jun 2007 00:28:18 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751184AbXF2E2I (ORCPT ); Fri, 29 Jun 2007 00:28:08 -0400 Received: from 74-93-104-97-Washington.hfc.comcastbusiness.net ([74.93.104.97]:38221 "EHLO sunset.davemloft.net" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1750752AbXF2E2F (ORCPT ); Fri, 29 Jun 2007 00:28:05 -0400 Date: Thu, 28 Jun 2007 21:28:25 -0700 (PDT) Message-Id: <20070628.212825.78710369.davem@davemloft.net> To: clameter@sgi.com Cc: hugh@veritas.com, James.Bottomley@steeleye.com, rmk+lkml@arm.linux.org.uk, akpm@linux-foundation.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] Containment measures for slab objects on scatter gather lists From: David Miller In-Reply-To: References: <20070628.211013.74747656.davem@davemloft.net> X-Mailer: Mew version 5.1.52 on Emacs 21.4 / Mule 5.0 (SAKAKI) Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1469 Lines: 31 From: Christoph Lameter Date: Thu, 28 Jun 2007 21:22:22 -0700 (PDT) > On Thu, 28 Jun 2007, David Miller wrote: > > > > Still a better solution would be to not use the slab allocator at all for > > > the objects that are used to send commands to the devices. These are not > > > permanent and grabbing a page from the pcp lists and putting it back is > > > likely as fast as performing a kmalloc. > > > > Jens Axboe wants to get references to the page structs behind > > kmalloc() allocated pages in his networking splice work. > > You can get such a reference and then the slab page will be in limbo if > all objects are freed until that reference is given up. The reference > method is also use by kmem_cache_vacate() (but that is slab internal). What about if someone kfree()'s that object meanwhile? Can we bump the SLAB object count just like we can a page? That's basically what's happening in the stuff Jens is working on, he needs to grab a reference to a SLAB object just like one can a page. Even if there is an intervening kfree (like a put_page()) the SLAB object is still live until all the references are put, and thus it can't get reallocated and given to another client by SLAB. - 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/