From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Thu, 27 Apr 2006 10:36:17 +0200 From: Jens Axboe Subject: Re: Lockless page cache test results Message-ID: <20060427083617.GO9211@suse.de> References: <20060426135310.GB5083@suse.de> <20060426095511.0cc7a3f9.akpm@osdl.org> <20060426174235.GC5002@suse.de> <20060426111054.2b4f1736.akpm@osdl.org> <20060426191557.GA9211@suse.de> <20060426131200.516cbabc.akpm@osdl.org> <20060427074533.GJ9211@suse.de> <4450796A.2030908@yahoo.com.au> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4450796A.2030908@yahoo.com.au> Sender: owner-linux-mm@kvack.org Return-Path: To: Nick Piggin Cc: Andrew Morton , torvalds@osdl.org, linux-kernel@vger.kernel.org, npiggin@suse.de, linux-mm@kvack.org List-ID: On Thu, Apr 27 2006, Nick Piggin wrote: > Jens Axboe wrote: > > >Things look pretty bad for the lockless kernel though, Nick any idea > >what is going on there? The splice change is pretty simple, see the top > >three patches here: > > Could just be the use of spin lock instead of read lock. > > I don't think it would be hard to convert find_get_pages_contig > to be lockless. Ah, certainly, it's not lockless like find_get_page(). Care to do such a patch? > Patched vanilla numbers look nicer, but I'm curious as to why > __do_page_cache was so bad before, if the file was in cache. > Presumably it should not more than double tree_lock acquisition... > it isn't getting called multiple times for each page, is it? It still does a lot of extra work that's completely wasted. With page_cache_readahead(), we should hit the RA_FLAG_INCACHE flag and be done with it. -- Jens Axboe -- 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