From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail202.messagelabs.com (mail202.messagelabs.com [216.82.254.227]) by kanga.kvack.org (Postfix) with ESMTP id 71EF96B00FE for ; Sat, 30 May 2009 19:20:26 -0400 (EDT) Date: Sat, 30 May 2009 16:18:13 -0700 From: "Larry H." Subject: Re: [patch 0/5] Support for sanitization flag in low-level page allocator Message-ID: <20090530231813.GP6535@oblivion.subreption.com> References: <20090530082048.GM29711@oblivion.subreption.com> <20090530173428.GA20013@elte.hu> <20090530180333.GH6535@oblivion.subreption.com> <20090530182113.GA25237@elte.hu> <20090530184534.GJ6535@oblivion.subreption.com> <20090530190828.GA31199@elte.hu> <4A21999E.5050606@redhat.com> <84144f020905301353y2f8c232na4c5f9dfb740eec4@mail.gmail.com> <20090530213311.GM6535@oblivion.subreption.com> <20090531001318.093e3665@lxorguk.ukuu.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090531001318.093e3665@lxorguk.ukuu.org.uk> Sender: owner-linux-mm@kvack.org To: Alan Cox Cc: Pekka Enberg , Rik van Riel , Ingo Molnar , linux-kernel@vger.kernel.org, Linus Torvalds , linux-mm@kvack.org, Ingo Molnar , pageexec@freemail.hu, Linus Torvalds List-ID: On 00:13 Sun 31 May , Alan Cox wrote: > > I was pointing out that the 'those test and jump/call branches have > > performance hits' argument, while nonsensical, applies to kzfree and > > with even more negative connotations (deeper call depth, more test > > branches used in ksize and kfree, lack of pointer validation). > > But they only apply to kzfree - there isn't a cost to anyone else. You've > move the decision to compile time which for the fast path stuff when you > just want to clear keys and other oddments is a big win. OK, I'm going to squeeze some time and provide patches that perform the same my original page bit ones did, but using kzfree. Behold code like in the tty buffer management, which uses the page allocator directly for allocations greater than PAGE_SIZE in length. That needs special treatment, and is exactly the reason I've proposed unconditional sanitization since the original patches were rejected. Larry -- 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