From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <43EEC136.5060609@yahoo.com.au> Date: Sun, 12 Feb 2006 16:01:42 +1100 From: Nick Piggin MIME-Version: 1.0 Subject: Re: Get rid of scan_control References: <20060211045355.GA3318@dmt.cnet> <20060211013255.20832152.akpm@osdl.org> <20060211014649.7cb3b9e2.akpm@osdl.org> <43EEAC93.3000803@yahoo.com.au> <43EEB4DA.6030501@yahoo.com.au> In-Reply-To: Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Christoph Lameter Cc: Andrew Morton , marcelo.tosatti@cyclades.com, linux-mm@kvack.org List-ID: Christoph Lameter wrote: > On Sun, 12 Feb 2006, Nick Piggin wrote: >>I think most of the cost apart from locking (because that will >>depend on contention) is hitting random cachelines of struct pages >>then hitting random radix tree cachelines to remove them. Not >>much you can do about that. >> >>That said I'm never against microoptimisations provided they >>weigh in on the right side of the (subjective) complexity / >>improvement ratio. > > > Its a bit strange if you call a function and then access a structure > member to get the result. Locating parameter in a structure makes it > impossible to see what is passed to a function when it is > called. > Sometimes there is more than one result though :\ > It is also something that will make it difficult for compilers to do > a good job. Flow control is easier to optimize for a local variable > than for a pointer into a struct that may have been modified elsewhere. > There are downsides to it. I was basically on the fence with its removal from mainline, because the complexity of parameters going to/from functions make the improvement borderline. But I would have kept it for my internal work, and given Marcelo is also interested in it I guess it could stay for now (unless you trump that with some performance numbers I guess). -- 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