From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f48.google.com (mail-pa0-f48.google.com [209.85.220.48]) by kanga.kvack.org (Postfix) with ESMTP id B84B96B0036 for ; Wed, 21 May 2014 18:42:53 -0400 (EDT) Received: by mail-pa0-f48.google.com with SMTP id rd3so1828574pab.21 for ; Wed, 21 May 2014 15:42:53 -0700 (PDT) Received: from mail.linuxfoundation.org (mail.linuxfoundation.org. [140.211.169.12]) by mx.google.com with ESMTP id ce7si30963647pad.113.2014.05.21.15.42.52 for ; Wed, 21 May 2014 15:42:52 -0700 (PDT) Date: Wed, 21 May 2014 15:42:50 -0700 From: Andrew Morton Subject: Re: [PATCH 0/4] pagecache scanning with /proc/kpagecache Message-Id: <20140521154250.95bc3520ad8d192d95efe39b@linux-foundation.org> In-Reply-To: <1400639194-3743-1-git-send-email-n-horiguchi@ah.jp.nec.com> References: <1400639194-3743-1-git-send-email-n-horiguchi@ah.jp.nec.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Naoya Horiguchi Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Konstantin Khlebnikov , Wu Fengguang , Arnaldo Carvalho de Melo , Borislav Petkov On Tue, 20 May 2014 22:26:30 -0400 Naoya Horiguchi wrote: > This patchset adds a new procfs interface to extrace information about > pagecache status. In-kernel tool tools/vm/page-types.c has already some > code for pagecache scanning without kernel's help, but it's not free > from measurement-disturbance, so here I'm suggesting another approach. I'm not seeing much explanation of why you think the kernel needs this. The overall justification for a change is terribly important so please do spend some time on it. As I don't *really* know what the patch is for, I can't comment a lot further, but... A much nicer interface would be for us to (finally!) implement fincore(), perhaps with an enhanced per-present-page payload which presents the info which you need (although we don't actually know what that info is!). This would require open() - it appears to be a requirement that the caller not open the file, but no reason was given for this. Requiring open() would address some of the obvious security concerns, but it will still be possible for processes to poke around and get some understanding of the behaviour of other processes. Careful attention should be paid to this aspect of any such patchset. -- 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