From mboxrd@z Thu Jan 1 00:00:00 1970 Subject: Re: [RFC 1/3] non-resident page tracking From: Peter Zijlstra In-Reply-To: <20050809182517.GA20644@dmt.cnet> References: <20050808201416.450491000@jumble.boston.redhat.com> <20050808202110.744344000@jumble.boston.redhat.com> <20050809182517.GA20644@dmt.cnet> Content-Type: text/plain Date: Tue, 09 Aug 2005 21:15:26 +0200 Message-Id: <1123614926.17222.19.camel@twins> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Marcelo Tosatti Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Rik van Riel List-ID: On Tue, 2005-08-09 at 15:25 -0300, Marcelo Tosatti wrote: > Hi Rik, > > Two hopefully useful comments: > > i) ARC and its variants requires additional information about page > replacement (namely whether the page has been reclaimed from the L1 or > L2 lists). > > How costly would it be to add this information to the hash table? > I've been thinking on reserving another word in the cache-line and use that as a bit-array to keep that information; the only problems with that would be atomicy of the {bucket,bit} tuple and very large cachelines where NUM_NR > 32. > ii) From my reading of the patch, the provided "distance" information is > relative to each hash bucket. I'm unable to understand the distance metric > being useful if measured per-hash-bucket instead of globally? The assumption is that IFF the hash function has good distribution properties the per bucket distance is a good approximation of (distance >> nonres_shift). > > PS: Since remember_page() is always called with the zone->lru_lock held, > the preempt_disable/enable pair is unecessary at the moment... still, > might be better to leave it there for safety reasons. > There being multiple zones; owning zone->lru_lock does not guarantee uniqueness on the remember_page() path as its a global structure. -- Peter Zijlstra -- 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