From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Morton Subject: Re: [PATCH v4] mm: add replace_page_cache_page() function Date: Tue, 18 Jan 2011 17:48:26 -0800 Message-ID: <20110118174826.4c6d47a3.akpm@linux-foundation.org> References: <20110118152844.88cfdc2c.akpm@linux-foundation.org> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: Miklos Szeredi , kamezawa.hiroyu@jp.fujitsu.com, nishimura@mxp.nes.nec.co.jp, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org To: Minchan Kim Return-path: In-Reply-To: Sender: owner-linux-mm@kvack.org List-Id: linux-fsdevel.vger.kernel.org On Wed, 19 Jan 2011 10:24:09 +0900 Minchan Kim wrote: > > > > This is all pretty ugly and inefficient. > > > > We call __remove_from_page_cache() which does a radix-tree lookup and > > then fiddles a bunch of accounting things. > > > > Then we immediately do the same radix-tree lookup and then undo the > > accounting changes which we just did. __And we do it in an open-coded > > fashion, thus giving the kernel yet another code site where various > > operations need to be kept in sync. > > > > Would it not be better to do a single radix_tree_lookup_slot(), > > overwrite the pointer therein and just leave all the ancilliary > > accounting unaltered? > > I agree single radix_tree_lookup but accounting still is needed since > newpage could be on another zone. What we can remove is just only > mapping->nrpages. Well. We only need to do inc/dec_zone_state if the zones are different. Perhaps the zones-equal case is worth optimising for, dunno. Also, the radix_tree_preload() should be unneeded. -- 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/ . Fight unfair telecom policy in Canada: sign http://dissolvethecrtc.ca/ Don't email: email@kvack.org