From mboxrd@z Thu Jan 1 00:00:00 1970 Subject: Re: [patch 4/8] mm: allow not updating BDI stats in end_page_writeback() From: Peter Zijlstra In-Reply-To: References: <20080317191908.123631326@szeredi.hu> <20080317191945.122011759@szeredi.hu> <1205840031.8514.346.camel@twins> <1205843375.8514.357.camel@twins> <1205845702.8514.365.camel@twins> Content-Type: text/plain Date: Tue, 18 Mar 2008 14:59:20 +0100 Message-Id: <1205848760.8514.366.camel@twins> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Miklos Szeredi Cc: akpm@linux-foundation.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org List-ID: On Tue, 2008-03-18 at 14:58 +0100, Miklos Szeredi wrote: > > > > So the thing that's in your way is that removing a page from the radix > > > > tree doesn't imply its done writing. So perhaps we should make that > > > > distinction instead? > > > > > > > > So instead of conditionally do part of the accounting, never do it and > > > > require something like: page_writeback_complete() to be called after a > > > > successfull test_clear_page_writeback(). > > > > > > Yes, that's a possibility, but then normal filesystems miss out on the > > > small optimization provided by doing the BDI accounting functions > > > inside the same IRQ disabled region as the radix tree operation. > > > Would that have any significant performance impact? > > > > Yeah, realized that. Don't know, would have to measure it somehow... > > some archs are rather slow with disabling IRQs, but we're talking about > > writeout which should be dominated by the IO times. > > > > Its just that your proposal exposes too much guts, I'd like the > > interface to be a little higher level. > > Well, but this is the kernel, you can't really make foolproof > interfaces. If we'll go with Andrew's suggestion, I'll add comments > warning users about not touching those flags unless they know what > they are doing, OK? Yeah, I guess so :-) -- 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