From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from flinx.npwt.net (eric@flinx.npwt.net [208.236.161.237]) by kvack.org (8.8.7/8.8.7) with ESMTP id OAA05331 for ; Mon, 13 Jul 1998 14:07:57 -0400 Subject: Re: More info: 2.1.108 page cache performance on low memory References: <199807131653.RAA06838@dax.dcs.ed.ac.uk> From: ebiederm+eric@npwt.net (Eric W. Biederman) Date: 13 Jul 1998 13:08:56 -0500 In-Reply-To: "Stephen C. Tweedie"'s message of Mon, 13 Jul 1998 17:53:55 +0100 Message-ID: Sender: owner-linux-mm@kvack.org To: "Stephen C. Tweedie" Cc: linux-mm@kvack.org List-ID: >>>>> "ST" == Stephen C Tweedie writes: ST> Hi all, ST> OK, a bit more benchmarking is showing bad problems with page ageing. ST> I've been running 2.1 with a big ramdisk and without, with page ageing ST> and without. The results for a simple compile job (make a few ST> dependency files then compile four .c files) look like this: ST> 2.0.34, 6m ram: 1:22 ST> 2.1.108, 16m ram, 10m ramdisk: ST> With page cache ageing: Not usable (swap death during boot.) ST> Without cache ageing: 8:47 ST> 2.1.108, 6m ram: ST> With page cache ageing: 4:14 ST> Without cache ageing: 3:22 O.k. Just a few thoughts. 1) We have a minimum size for the buffer cache in percent of physical pages. Setting the minimum to 0% may help. 2) If we play with LRU list it may be most practical use page->next and page->prev fields for the list, and for truncate_inode_pages && invalidate_inode_pages do something like: for(i = 0; i < inode->i_size; i+= PAGE_SIZE) { page = find_in_page_cache(inode, i); if (page) /* remove it */ ; } And remove the inode->i_pages list. This should be roughly equivalent to the bforgets needed by truncate anyway so should impose not large peformance penalty. Personally I think it is broken to set the limits of cache sizes (buffer & page) to anthing besides: max=100% min=0% by default. But now that we have this hand tuneing option in addition to auto tuning we should experiment with it as well. Eric -- This is a majordomo managed list. To unsubscribe, send a message with the body 'unsubscribe linux-mm me@address' to: majordomo@kvack.org