From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from penguin.e-mind.com (penguin.e-mind.com [195.223.140.120]) by kvack.org (8.8.7/8.8.7) with ESMTP id OAA19172 for ; Wed, 13 Jan 1999 14:09:58 -0500 Date: Wed, 13 Jan 1999 19:52:03 +0100 (CET) From: Andrea Arcangeli Subject: Re: [PATCH] Re: MM deadlock [was: Re: arca-vm-8...] In-Reply-To: <199901131755.RAA06476@dax.scot.redhat.com> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org To: "Stephen C. Tweedie" Cc: Linus Torvalds , Rik van Riel , Zlatko Calusic , "Eric W. Biederman" , Savochkin Andrey Vladimirovich , steve@netplus.net, brent verner , "Garst R. Reese" , Kalle Andersson , Ben McCann , Alan Cox , bredelin@ucsd.edu, linux-kernel@vger.rutgers.edu, linux-mm@kvack.org List-ID: On Wed, 13 Jan 1999, Stephen C. Tweedie wrote: > I think this is the wrong solution: far better to do the patch below, > which simply exempts reads from nr_async_pages altogether. I > originally added nr_async_pages to serve two functions: to allow > kswapd to determine how much memory it was already in the process of > freeing, and to act as a throttle on the number of write IOs submitted > when swapping. > > We don't need a similar throttling action for reads, because every > place where we do VM readahead, each readahead IO cluster is followed > by a synchronous read on one page. We don't throttle the async > readaheads on normal file IO, for example. Note that we don't need nr_async_pages at all. Here when the limit of nr_async_pages is low it's only a bottleneck for swapout performances. I have not removed it (because it could be useful to decrease swapout I/O if somebody needs this strange feature), but I have added a page_daemon.max_async_pages and set it to something like 256. Now I check nr_async_pages against the new max_async_pages. I _guess_ (not checked) that the _only_ reason Steve seen arca-vm-16 so high improved changing SWAP_CLUSTER_MAX to 512 instead of 32 is the removal of the nr_async_pages bottleneck. Andrea Arcangeli -- This is a majordomo managed list. To unsubscribe, send a message with the body 'unsubscribe linux-mm me@address' to: majordomo@kvack.org