From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Sun, 19 Jul 1998 00:10:09 +0200 (CEST) From: Rik van Riel Reply-To: Rik van Riel Subject: Re: cp file /dev/zero <-> cache [was Re: increasing page size] In-Reply-To: <199807131342.OAA06485@dax.dcs.ed.ac.uk> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org To: "Stephen C. Tweedie" Cc: "Benjamin C.R. LaHaise" , Linux MM List-ID: On Mon, 13 Jul 1998, Stephen C. Tweedie wrote: > I'm working on it right now. Currently, the VM is so bad that it is > seriously getting in the way of my job. Just trying to fix some odd > swapper bugs is impossible to test because I can't set up a ramdisk for > swap and do in-memory tests that way: things thrash incredibly. The > algorithms for aggressive cache pruning rely on fractions of > nr_physpages, and that simply doesn't work if you have large numbers of > pages dedicated to non-swappable things such as ramdisk, bigphysarea DMA > buffers or network buffers. This means we'll have to substract those pages before determining the used percentage. > Rik, unfortunately I think we're just going to have to back out your > cache page ageing. I've just done that on my local test box and the > results are *incredible*: OK, I don't see much problems with that, except that the aging helps a _lot_ with readahead. For the rest, it's not much more than a kludge anyway ;( We really ought to do better than that anyway. I'll give you guys the URL of the Digital Unix manuals on this... (they have some _very_ nice mechanisms for this) > I'm going to do a bit more experimenting to see if we can keep some of > the good ageing behaviour by doing proper LRU in the cache, but > otherwise I think the cache ageing has either got to go or to be > drastically altered. A 2-level LRU on the page cache would be _very_ nice, but probably just as desastrous wrt. fragmentation as aging... Rik. +-------------------------------------------------------------------+ | Linux memory management tour guide. H.H.vanRiel@phys.uu.nl | | Scouting Vries cubscout leader. http://www.phys.uu.nl/~riel/ | +-------------------------------------------------------------------+ -- This is a majordomo managed list. To unsubscribe, send a message with the body 'unsubscribe linux-mm me@address' to: majordomo@kvack.org