From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Sun, 05 Sep 2004 10:36:32 -0700 From: "Martin J. Bligh" Subject: Re: [RFC][PATCH 0/3] beat kswapd with the proverbial clue-bat Message-ID: <503530000.1094405791@[10.10.2.4]> In-Reply-To: References: <413AA7B2.4000907@yahoo.com.au> <20040904230210.03fe3c11.davem@davemloft.net><413AAF49.5070600@yahoo.com.au> <413AE6E7.5070103@yahoo.com.au> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline Sender: owner-linux-mm@kvack.org Return-Path: To: Linus Torvalds , Nick Piggin Cc: "David S. Miller" , akpm@osdl.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org List-ID: >> Hmm, and the crowning argument for not stopping at order 3 is that if we >> never use higher order allocations, nothing will care about their watermarks >> anyway. I think I had myself confused when that question in the first place. >> >> So yeah, stopping at a fixed number isn't required, and as you say it keeps >> things general and special cases minimal. > > Hey, please refute my "you need 20% free" to get even to order-3 for most > cases first. > > It's probably acceptable to have a _very_ backgrounded job that does > freeing if order-3 isn't available, but it had better be pretty > slow-moving, I suspect. On the order of "It's probably ok to try to aim > for up to 25% free 'overnight' if the machine is idle" but it's almost > certainly not ok to aggressively push things out to that degree.. IIRC, the way we free pages is basically random shootdown. We don't even attempt to free pages in a contiguous block, so it's unsuprising it doesn't work. Now we have rmap, we should be able to walk through a block, see if everything in it looks swappable, and then try to shoot it down. If not, move onto the next one. I think that'd be a damned sight more likely to free things up for higher order allocs if they do happen. M. -- 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: aart@kvack.org