From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Thu, 11 May 2000 17:09:48 -0700 (PDT) From: Linus Torvalds Subject: Re: [PATCH] Recent VM fiasco - fixed In-Reply-To: <20000511193858.A402@stormix.com> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org Return-Path: To: Simon Kirby Cc: linux-mm@kvack.org, linux-kernel@vger.rutgers.edu List-ID: On Thu, 11 May 2000, Simon Kirby wrote: > > Hrm! pre7 release seems to be even better. 113 vmstat-line-seconds now > (yes, I know this isn't a very scientific testing method :)). Second try > was 114 vmstat-line-seconds. classzone-27 did it in 107, so that's not > very far off! Also, it swapped much less this time, and used less CPU. > vmstat output attached. The final pre7 did something that I'm not entirely excited about, but that kind of makes sense at least from a CPU standpoint (as the SGI people have repeated multiple times). What the real pre7 does is to just move any page that has problems getting free'd to the head of the LRU list, so that we won't try it immediately the next time. This way we don't test the same pages over and over again when they are either shared, in the wrong zone, or have dirty/locked buffers. It means that the "LRU" is less LRU, but you could see it as a "how hard do we want to free this" pressure-based system that really a least recently _used_ system. And it avoids the "repeat the whole thing on the same page" issue. And it looks like it behaves reasonably well, while saving a lot of CPU. Knock wood. I'm still considering the pre7 as more a "ok, I tried to get rid of the cruft" thing. Most of the special case code that has accumulated lately is gone. We can start adding stuff back now, I'm happy that the basics are reasonably clean. I think Ingo already posted a very valid concern about high-memory machines, and there are other issues we should look at. I just want to be in a position where we can look at the code and say "we do X because Y", rather than a collection of random tweaks that just happens to work. Linus -- 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.eu.org/Linux-MM/