From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qg0-f52.google.com (mail-qg0-f52.google.com [209.85.192.52]) by kanga.kvack.org (Postfix) with ESMTP id 277CD6B0035 for ; Thu, 11 Sep 2014 22:33:14 -0400 (EDT) Received: by mail-qg0-f52.google.com with SMTP id i50so100172qgf.11 for ; Thu, 11 Sep 2014 19:33:13 -0700 (PDT) Received: from mx1.redhat.com (mx1.redhat.com. [209.132.183.28]) by mx.google.com with ESMTPS id j4si4061486qgf.81.2014.09.11.19.33.10 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 11 Sep 2014 19:33:13 -0700 (PDT) Date: Thu, 11 Sep 2014 22:32:52 -0400 (EDT) From: Mikulas Patocka Subject: Re: [PATCH] slab: implement kmalloc guard In-Reply-To: Message-ID: References: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org List-ID: To: Christoph Lameter Cc: Pekka Enberg , David Rientjes , Joonsoo Kim , Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org, "Alasdair G. Kergon" , Mike Snitzer , Milan Broz , kkolasa@winsoft.pl, dm-devel@redhat.com On Mon, 8 Sep 2014, Christoph Lameter wrote: > On Mon, 8 Sep 2014, Mikulas Patocka wrote: > > > I don't know what you mean. If someone allocates 10000 objects with sizes > > from 1 to 10000, you can't have 10000 slab caches - you can't have a slab > > cache for each used size. Also - you can't create a slab cache in > > interrupt context. > > Oh you can create them up front on bootup. And I think only the small > sizes matter. Allocations >=8K are pushed to the page allocator anyways. Only for SLUB. For SLAB, large allocations are still use SLAB caches up to 4M. But anyway - having 8K preallocated slab caches is too much. If you want to integrate this patch into the slab/slub subsystem, a better solution would be to store the exact size requested with kmalloc along the slab/slub object itself (before the preceding redzone). But it would result in duplicating the work - you'd have to repeat the logic in this patch three times - once for slab, once for slub and once for kmalloc_large/kmalloc_large_node. I don't know if it would be better than this patch. > > > We already have a redzone structure to check for writes over the end of > > > the object. Lets use that. > > > > So, change all three slab subsystems to use that. > > SLOB has no debugging features and I think that was intentional. We are > trying to unify the debug checks etc. Some work on that would be > appreciated. I think the kmalloc creation is already in slab_common.c Mikulas -- 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