From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <44505D75.8070409@yahoo.com.au> Date: Thu, 27 Apr 2006 15:58:13 +1000 From: Nick Piggin MIME-Version: 1.0 Subject: Re: Lockless page cache test results References: <20060426135310.GB5083@suse.de> <20060426095511.0cc7a3f9.akpm@osdl.org> <20060426174235.GC5002@suse.de> <20060426111054.2b4f1736.akpm@osdl.org> <20060426182323.GI5002@suse.de> <20060426114649.5a0e0dea.akpm@osdl.org> In-Reply-To: <20060426114649.5a0e0dea.akpm@osdl.org> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Andrew Morton Cc: Jens Axboe , linux-kernel@vger.kernel.org, npiggin@suse.de, linux-mm@kvack.org List-ID: Andrew Morton wrote: > Jens Axboe wrote: > >>Are there cases where the lockless page cache performs worse than the >>current one? > > > Yeah - when human beings try to understand and maintain it. Have any tried yet? ;) I won't deny it is complex (because I don't like when I make the same point and people go on to take great trouble to convince me how simple it is!). But I hope it isn't _too_ bad. It is basically a dozen line function at the core, and that gets used to implement find_get_page, find_lock_page. Their semantics remain the same, so that's where the line is drawn (plus minor things, like an addition for reclaim's remove-from-pagecache protocol). IMO the rcu radix tree is probably the most complex bit... but that pales in comparison to things like our prio tree, or RCU trie. > > The usual tradeoffs apply ;) Definitely. It isn't fun if you just take the patch and merge it. -- SUSE Labs, Novell Inc. Send instant messages to your online friends http://au.messenger.yahoo.com -- 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