From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Wed, 31 May 2006 08:13:41 -0700 (PDT) From: Linus Torvalds Subject: Re: [rfc][patch] remove racy sync_page? In-Reply-To: <447DAEDE.5070305@yahoo.com.au> Message-ID: References: <447AC011.8050708@yahoo.com.au> <20060529121556.349863b8.akpm@osdl.org> <447B8CE6.5000208@yahoo.com.au> <20060529183201.0e8173bc.akpm@osdl.org> <447BB3FD.1070707@yahoo.com.au> <447BD31E.7000503@yahoo.com.au> <447BD63D.2080900@yahoo.com.au> <447CE43A.6030700@yahoo.com.au> <447D9A41.8040601@yahoo.com.au> <447DAEDE.5070305@yahoo.com.au> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org Return-Path: To: Nick Piggin Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, mason@suse.com, andrea@suse.de, hugh@veritas.com, axboe@suse.de List-ID: On Thu, 1 Jun 2006, Nick Piggin wrote: > > > And yes, we used to have explicit unplugging (a long long long time ago), > > and IT SUCKED. People would forget, but even more importantly, people would > > do it even when not > > I don't see what the problem is. Locks also suck if you forget to unlock > them. Locks are simple, and in fact are _made_ simple on purpose. We try very hard to unlock in the same function that we lock, for example. Because if we don't, bugs happen. That's simply not _practical_ for IO. Think about it. Quite often, the waiting is done somewhere else than the actual submission. > > needed because they didn't have a good place to do it because the waiter was > > in a totally different path. > > Example? Pretty much all of them. Where do you wait for IO? Would you perhaps say "wait_on_page()"? In other words, we really _do_ exactly what you think we should do. > I don't know why you think this way of doing plugging is fundamentally > right and anything else must be wrong... it is always heuristic, isn't > it? A _particular_ way of doing plugging is not "fundamentally right". I'm perfectly happy with chaning the place we unplug, if people want that. We've done it several times. But plugging as a _concept_ is definitely fundamentally right, exactly because it allows us to have the notion of "plug + n* + unplug". And you were not suggesting moving unplugging around. You were suggesting removing the feature. Which is when I said "no f*cking way!". Linus -- 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