From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Wed, 7 Jun 2000 14:32:42 +0100 From: "Stephen C. Tweedie" Subject: Re: [PATCH] VM kswapd autotuning vs. -ac7 Message-ID: <20000607143242.D30951@redhat.com> References: Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: ; from cr@sap.com on Wed, Jun 07, 2000 at 12:23:36PM +0200 Sender: owner-linux-mm@kvack.org Return-Path: To: Christoph Rohland Cc: Rik van Riel , linux-mm@kvack.org List-ID: Hi, On Wed, Jun 07, 2000 at 12:23:36PM +0200, Christoph Rohland wrote: > Rik van Riel writes: > > > Awaiting your promised integration of SHM with the shrink_mmap > > queue... > > Sorry Rik, there was a misunderstanding here. I would really like to > have this integration. But AFAICS this is a major task. shrink_mmap > relies on the pages to be in the page cache and the pagecache does not > handle shared anonymous pages. The swap cache --- which does handle anonymous pages --- is IN the page cache. The main reason SHM needs its own swap code is that normal anonymous pages are referred to only from ptes --- the ptes either point to the physical page containing the page, or to the swap entry. We cannot use that for SHM, because SysV SHM segments must be persistent even if there are no attachers, and hence no ptes to maintain the location of the pages. If it wasn't for persistent SHM segments, it would be trivial to integrate SHM into the normal swapper. Cheers, Stephen -- 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/