From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail144.messagelabs.com (mail144.messagelabs.com [216.82.254.51]) by kanga.kvack.org (Postfix) with SMTP id 5D9076B009E for ; Fri, 12 Jun 2009 12:05:20 -0400 (EDT) Message-ID: <4A327CB1.6060009@redhat.com> Date: Fri, 12 Jun 2009 12:05:05 -0400 From: Rik van Riel MIME-Version: 1.0 Subject: Re: [PATCH 1/5] HWPOISON: define VM_FAULT_HWPOISON to 0 when feature is disabled References: <20090611142239.192891591@intel.com> <20090611144430.414445947@intel.com> <20090612112258.GA14123@elte.hu> <20090612125741.GA6140@localhost> <20090612131754.GA32105@elte.hu> <20090612153501.GA5737@elte.hu> In-Reply-To: <20090612153501.GA5737@elte.hu> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: Ingo Molnar Cc: Linus Torvalds , Wu Fengguang , Thomas Gleixner , "H. Peter Anvin" , Peter Zijlstra , Andrew Morton , LKML , Nick Piggin , Hugh Dickins , Andi Kleen , "chris.mason@oracle.com" , "linux-mm@kvack.org" List-ID: Ingo Molnar wrote: > So i think hwpoison simply does not affect our ability to get log > messages out - but it sure allows crappier hardware to be used. > Am i wrong about that for some reason? You are :) A 2-bit memory error can be a temporary failure, eg. due to a cosmic ray. If bit errors could be prevented in hardware, there would be no reason to have ECC at all. The only reason to stop using that page is because we do not know for sure whether the error was temporary or permanent (or dependent on a particular bit pattern). Userspace needs to be notified that some data disappeared, if it did - for clean pagecache and swap cache pages, the kernel can simply take the page away and wait for a page fault... The sysadmin needs to know that something happened too, because the hardware *might* have a problem. However, a 2-bit error does not imply that the hardware actually needs to be replaced. -- All rights reversed. -- 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