From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from alogconduit1ah.ccr.net (ccr@alogconduit1ao.ccr.net [208.130.159.15]) by kvack.org (8.8.7/8.8.7) with ESMTP id KAA02361 for ; Mon, 26 Apr 1999 10:42:30 -0400 Subject: Re: 2.2.6_andrea2.bz2 References: From: ebiederm+eric@ccr.net (Eric W. Biederman) Date: 26 Apr 1999 09:44:36 -0500 In-Reply-To: Andrea Arcangeli's message of "Mon, 26 Apr 1999 15:06:40 +0200 (CEST)" Message-ID: Sender: owner-linux-mm@kvack.org To: Andrea Arcangeli Cc: linux-kernel@vger.rutgers.edu, linux-mm@kvack.org List-ID: >>>>> "AA" == Andrea Arcangeli writes: AA> On 26 Apr 1999, Eric W. Biederman wrote: >> The real gain of this is not so much in the current cases we are fast at >> but for things like network, and compressed files (in general anything that AA> Could you produce an example (also "look at file.c" will be ok ;) to allow AA> me to see which are the issues with network and compressed files? Thanks. The primary one is they can't use the buffer cache so they must roll their own caching mechanism. Look at the smbfs version of updatepage. (write through!) Look at e2compr which doesn't compress data until the file is closed! It writes the data uncompressed, and then at iput time rewrites the file compressed. Run a moderately early version of fat_cvf/dmsdos, before they found out how to use the buffer cache, and watch it crawl on a read-only fs. nfs doesn't periodically flush dirty data, to keep the volume low. It does flush on file close (which helps, and is as correct as possible for nfs), but you can still find I haven't seen any provision in any of these roll your own solutions for flushing the dirty buffers when the system is low on memory. Etc. The point is that because there isn't a caching subsystem all of the filesystems above have to roll their own. And because they roll their own the code is less polished than a solution which would work for all of them would be. Eric -- To unsubscribe, send a message with 'unsubscribe linux-mm my@address' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://humbolt.geo.uu.nl/Linux-MM/