From mboxrd@z Thu Jan 1 00:00:00 1970 From: mel@skynet.ie (Mel Gorman) Subject: Re: [00/41] Large Blocksize Support V7 (adds memmap support) Date: Tue, 11 Sep 2007 22:54:29 +0100 Message-ID: <20070911215429.GA25565@skynet.ie> References: <20070911060349.993975297@sgi.com> <200709111144.48743.nickpiggin@yahoo.com.au> <20070911205350.GA18127@skynet.ie> <200709111600.18756.nickpiggin@yahoo.com.au> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Cc: Nick Piggin , andrea@suse.de, torvalds@linux-foundation.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, Christoph Hellwig , William Lee Irwin III , David Chinner , Jens Axboe , Badari Pulavarty , Maxim Levitsky , Fengguang Wu , swin wang , totty.lu@gmail.com, hugh@veritas.com, joern@lazybastard.org To: Christoph Lameter Return-path: Received: from gir.skynet.ie ([193.1.99.77]:40380 "EHLO gir.skynet.ie" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755058AbXIKVyd (ORCPT ); Tue, 11 Sep 2007 17:54:33 -0400 Content-Disposition: inline In-Reply-To: Sender: linux-fsdevel-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org On (11/09/07 14:48), Christoph Lameter didst pronounce: > On Tue, 11 Sep 2007, Nick Piggin wrote: > > > But that's not my place to say, and I'm actually not arguing that high > > order pagecache does not have uses (especially as a practical, > > shorter-term solution which is unintrusive to filesystems). > > > > So no, I don't think I'm really going against the basics of what we agreed > > in Cambridge. But it sounds like it's still being billed as first-order > > support right off the bat here. > > Well its seems that we have different interpretations of what was agreed > on. My understanding was that the large blocksize patchset was okay > provided that I supply an acceptable mmap implementation and put a > warning in. > Warnings == #2 citizen in my mind with known potential failure cases. That was the point I thought. > > But even so, you can just hold an open fd in order to pin the dentry you > > want. My attack would go like this: get the page size and allocation group > > size for the machine, then get the number of dentries required to fill a > > slab. Then read in that many dentries and pin one of them. Repeat the > > process. Even if there is other activity on the system, it seems possible > > that such a thing will cause some headaches after not too long a time. > > Some sources of pinned memory are going to be better than others for > > this of course, so yeah maybe pagetables will be a bit easier (I don't know). > > Well even without slab targeted reclaim: Mel's antifrag will sort the > dentries into separate blocks of memory and so isolate the issue. -- Mel Gorman Part-time Phd Student Linux Technology Center University of Limerick IBM Dublin Software Lab