From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752951AbXDMCVe (ORCPT ); Thu, 12 Apr 2007 22:21:34 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752969AbXDMCVe (ORCPT ); Thu, 12 Apr 2007 22:21:34 -0400 Received: from smtp109.mail.mud.yahoo.com ([209.191.85.219]:31654 "HELO smtp109.mail.mud.yahoo.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1752927AbXDMCVd (ORCPT ); Thu, 12 Apr 2007 22:21:33 -0400 DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=s1024; d=yahoo.com.au; h=Received:X-YMail-OSG:Message-ID:Date:From:User-Agent:X-Accept-Language:MIME-Version:To:CC:Subject:References:In-Reply-To:Content-Type:Content-Transfer-Encoding; b=C0q+16yckqmC/wX+uZgtv/4DTuH8SMkb2P2KYRNgEXSPxfyaxngbY+QzvlEwS4KOLLz5Xn4Grz0zKCFgPgS4DQ+2vVpzPU0+2d9p2XJ0CVZBxVxRJ1MzxsBYwlOh6XT1eevSQCQuzBjlwl7C71+4p4LQdFYq2OnnP3OQJmHy1hA= ; X-YMail-OSG: 82hfw0YVM1nkXrQPv0AacqiFBE3iFoQMDUE2y.KvA09pQ83ENeHYXFYshVsXolmjMvtr4uOFNw-- Message-ID: <461EE925.1000301@yahoo.com.au> Date: Fri, 13 Apr 2007 12:21:25 +1000 From: Nick Piggin User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.7.12) Gecko/20051007 Debian/1.7.12-1 X-Accept-Language: en MIME-Version: 1.0 To: Matt Mackall CC: Andrew Morton , William Lee Irwin III , linux-kernel@vger.kernel.org Subject: Re: [PATCH 0/13] maps: pagemap, kpagemap, and related cleanups References: <1.486631555@selenic.com> <20070412231050.GN2986@holomorphy.com> <20070412163235.dd030637.akpm@linux-foundation.org> <461ECB9C.8060000@yahoo.com.au> <20070412174201.065068b2.akpm@linux-foundation.org> <461ED96C.5030606@yahoo.com.au> <20070412182213.a18cc4a7.akpm@linux-foundation.org> <461EE005.6070605@yahoo.com.au> <20070413015712.GL11115@waste.org> In-Reply-To: <20070413015712.GL11115@waste.org> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Matt Mackall wrote: > On Fri, Apr 13, 2007 at 11:42:29AM +1000, Nick Piggin wrote: >>If kprobes is simply crappy and doesn't work properly for this, then I >>could accept that. I'm not someone trying to get this info. So why can't >>it be used? (not just for kpagemap, but for clear_refs and all that gunk >>too). > > > kprobes is good for looking at events, but bad for looking at state. > Especially metric shitloads of state. Why? Why is a kprobes trap significantly more expensive than a read syscall? >>Maybe. How about LRU? Reclaim performance is bad, and you want to work out >>which pages keep going off the end of it, or which pages keep getting >>written out via it, or who's pages are on the active list, forcing mine >>out. > > > Those are actually probably a good match for systemtap as they're all events. Traverse the LRU? Which files do they belong to? What process maps them? -- SUSE Labs, Novell Inc.