From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <4021A62D.40002@cyberone.com.au> Date: Thu, 05 Feb 2004 13:10:53 +1100 From: Nick Piggin MIME-Version: 1.0 Subject: Re: [PATCH 3/5] mm improvements References: <4020BE45.10007@cyberone.com.au> <16417.8644.203682.640759@laputa.namesys.com> In-Reply-To: <16417.8644.203682.640759@laputa.namesys.com> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Nikita Danilov Cc: Rik van Riel , Andrew Morton , linux-mm@kvack.org List-ID: Nikita Danilov wrote: >Rik van Riel writes: > > On Wed, 4 Feb 2004, Nick Piggin wrote: > > > Nick Piggin wrote: > > > > > > > 3/5: vm-lru-info.patch > > > > Keep more referenced info in the active list. Should also improve > > > > system time in some cases. Helps swapping loads significantly. > > > > I suspect this is one of the more important ones in this > > batch of patches... > >I don't understand how this works. This patch just parks mapped pages on >the "ignored" segment of the active list, where they rest until >reclaim_mapped mode is entered. > >This only makes a difference for the pages that were page_referenced(): > >1. they are moved to the ignored segment rather than to the head of the >active list. > >2. their referenced bit is not cleared > > It treats all mapped pages in the same manner. Without this patch, referenced mapped pages are distinctly disadvantaged vs unreferenced mapped pages. Even if reclaim_mapped is only flipped once every few seconds it can make a big impact. On a 64MB heavily swapping, you probably take 10 seconds to reclaim 64MB. It is of critical importance that we keep as much hotness information as possible. It shows on the benchmarks too. It provides nearly as much improvement as your patch alone for a make -j16. ie. over 20% http://www.kerneltrap.org/~npiggin/vm/2/ Also, when you're heavily swapping, everything slows down to such an extent that "hot" pages are no longer touched thousands of times per second, but maybe a few times every few seconds. If you're continually clearing this information, as soon as reclaim_mapped is triggered, all your hot pages get evicted. -- 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: aart@kvack.org