From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Wed, 02 Jul 2003 13:05:01 -0700 From: "Martin J. Bligh" Subject: Re: What to expect with the 2.6 VM Message-ID: <542640000.1057176301@flay> In-Reply-To: References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline Sender: owner-linux-mm@kvack.org Return-Path: To: Rik van Riel , Andrea Arcangeli Cc: Mel Gorman , Linux Memory Management List , Linux Kernel Mailing List List-ID: >> So ether we declare 32bit archs obsolete in production with 2.6, or we >> drop rmap behind remap_file_pages. > >> Something has to change since IMHO in the current 2.5.73 remap_file_pages >> is nearly useless. > > Agreed. What we did for a certain unspecified kernel tree > at Red Hat was the following: > > 1) limit sys_remap_file_pages functionality to shared memory > segments on ramfs (unswappable) and tmpfs (mostly unswappable;)) > > 2) have the VMAs with remapped pages in them marked VM_LOCKED > > 3) do not set up pte chains for the pages that get mapped with > install_page > > 4) remove said pages from the LRU list, in the ramfs case, they're > unswappable anyway so we shouldn't have the VM scan them > > The only known user of sys_remap_file_pages was more than happy > to have the functionality limited to just what they actually need, > in order to get simpler code with less overhead. > > Lets face it, nobody is going to use sys_remap_file_pages for > anything but a database shared memory segment anyway. You don't > need to care about truncate or the other corner cases. Well if RH have done this internally, and they invented the thing, then I see no reason not do that in 2.5 ... >> Maybe I'm just taking this out of context, and it's twisting my brain, >> but as far as I know, the nonlinear vma's *are* backed by pte_chains. > > Rik: > > They are, but IMHO they shouldn't be. The nonlinear vmas are used > only for database shared memory segments and other "bypass the VM" > applications, so I don't see any reason why we need to complicate > things hopelessly in order to deal with corner cases like truncate. Agreed. Oddly, most of us seem to agree on this ... ;-) M. -- 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-mm.org/ . Don't email: aart@kvack.org