From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx115.postini.com [74.125.245.115]) by kanga.kvack.org (Postfix) with SMTP id 988FA6B006C for ; Wed, 2 Jan 2013 09:32:17 -0500 (EST) Date: Wed, 2 Jan 2013 14:32:16 +0000 From: Christoph Lameter Subject: Re: [PATCH 1/2] tmpfs mempolicy: fix /proc/mounts corrupting memory In-Reply-To: Message-ID: <0000013bfbad4630-c888f29b-7294-4685-8164-87e2fb136796-000000@email.amazonses.com> References: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org List-ID: To: Hugh Dickins Cc: Linus Torvalds , Andrew Morton , Lee Schermerhorn , KOSAKI Motohiro , David Rientjes , Mel Gorman , Ingo Molnar , Peter Zijlstra , linux-kernel@vger.kernel.org, linux-mm@kvack.org On Wed, 2 Jan 2013, Hugh Dickins wrote: > Recent NUMA enhancements are not to blame: this dates back to 2.6.35, > when commit e17f74af351c "mempolicy: don't call mpol_set_nodemask() > when no_context" skipped mpol_parse_str()'s call to mpol_set_nodemask(), > which used to initialize v.preferred_node, or set MPOL_F_LOCAL in flags. > With slab poisoning, you can then rely on mpol_to_str() to set the bit > for node 0x6b6b, probably in the next page above the caller's stack. Ugly. But 2.6.35 means that the patch was not included in several enterprise linux releases. > I don't understand why MPOL_LOCAL is described as a pseudo-policy: > it's a reasonable policy which suffers from a confusing implementation > in terms of MPOL_PREFERRED with MPOL_F_LOCAL. I believe this would be > much more robust if MPOL_LOCAL were recognized in switch statements > throughout, MPOL_F_LOCAL deleted, and MPOL_PREFERRED use the (possibly > empty) nodes mask like everyone else, instead of its preferred_node > variant (I presume an optimization from the days before MPOL_LOCAL). > But that would take me too long to get right and fully tested. The current approaches to implementing NUMA scheduling are making MPOL_LOCAL an explicit policy. See https://patchwork.kernel.org/patch/1703641/. Does that address the concerns? -- 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