From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Thu, 31 Jul 2008 07:40:39 -0500 From: Jack Steiner Subject: Re: GRU driver feedback Message-ID: <20080731124039.GA27329@sgi.com> References: <20080723141229.GB13247@wotan.suse.de> <20080729185315.GA14260@sgi.com> <200807301550.34500.nickpiggin@yahoo.com.au> <200807311714.05252.nickpiggin@yahoo.com.au> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <200807311714.05252.nickpiggin@yahoo.com.au> Sender: owner-linux-mm@kvack.org Return-Path: To: Nick Piggin Cc: Robin Holt , "Torvalds, Linus" , Nick Piggin , Andrew Morton , Linux Memory Management List , Linux Kernel Mailing List List-ID: On Thu, Jul 31, 2008 at 05:14:04PM +1000, Nick Piggin wrote: > On Wednesday 30 July 2008 15:50, Nick Piggin wrote: > > On Wednesday 30 July 2008 04:53, Robin Holt wrote: > > > > In the case where unmap_region is clearing page tables, the caller to > > > unmap_region is expected to be holding the mmap_sem writably. Jacks > > > fault handler will immediately return when it fails on the > > > down_read_trylock(). > > > > No, you are right of course. I had in my mind the problems faced by > > lockless get_user_pages, in which case I was worried about the page table > > existence, but missed the fact that you're holding mmap_sem to provide > > existence (which it would, as you note, although one day we may want to > > reclaim page tables or something that doesn't take mmap_sem, so a big > > comment would be nice here). > > The other thing is... then GRU should get rid of the local_irq_disable > in the atomic pte lookup. By definition it is worthless if we can be > operating on an mm that is not running on current (and if I understand > correctly, sn2 can avoid sending tlb flush IPIs completely sometimes?) Done. I'm collecting the fixes & additional comments to be added & will send them upstream later. Thanks for the careful review. --- jack -- 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: email@kvack.org