From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Thu, 1 Feb 2001 14:45:04 -0200 (BRDT) From: Rik van Riel Subject: Re: [PATCH] vma limited swapin readahead In-Reply-To: <20010201143606.P11607@redhat.com> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org Return-Path: To: "Stephen C. Tweedie" Cc: Marcelo Tosatti , David Gould , "Eric W. Biederman" , lkml , linux-mm@kvack.org List-ID: On Thu, 1 Feb 2001, Stephen C. Tweedie wrote: > On Thu, Feb 01, 2001 at 08:53:33AM -0200, Marcelo Tosatti wrote: > > On Thu, 1 Feb 2001, Stephen C. Tweedie wrote: > > > > If we're under free memory shortage, "unlucky" readaheads will be harmful. > > I know, it's a balancing act. But given that even one > successful readahead per read will halve the number of swapin > seeks, the performance loss due to the extra scavenging has got > to be bad to outweigh the benefit. But only when the extra pages we're reading in don't displace useful data from memory, making us fault in those other pages ... causing us to go to the disk again and do more readahead, which could potentially displace even more pages, etc... One solution could be to put (most of) the swapin readahead pages on the inactive_dirty list, so pressure by readahead on the resident pages is smaller and the not used readahead pages are reclaimed faster. (and with the size of the inactive list being 1 second worth of page steals, those pages still have a good chance of being used before they're being recycled) regards, Rik -- Virtual memory is like a game you can't win; However, without VM there's truly nothing to lose... http://www.surriel.com/ http://www.conectiva.com/ http://distro.conectiva.com.br/ -- 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/