From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Wed, 30 Apr 2003 20:45:51 -0700 From: William Lee Irwin III Subject: Re: [PATCH] remove unnecessary PAE pgd set Message-ID: <20030501034551.GB20911@holomorphy.com> References: <3EB05F61.5070404@us.ibm.com> <20030501032215.GA20911@holomorphy.com> <3EB096D8.80905@us.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <3EB096D8.80905@us.ibm.com> Sender: owner-linux-mm@kvack.org Return-Path: To: Dave Hansen Cc: Andrew Morton , linux-mm@kvack.org List-ID: William Lee Irwin III wrote: >> I suspect this set_pgd() should go away for non-PAE also. On Wed, Apr 30, 2003 at 08:39:04PM -0700, Dave Hansen wrote: > Wouldn't it be analogous to the PMD set with PAE on, and necessary? > Since processes don't share PGDs in 4G mode, the PGD entry could be > missing in a process's pagetables after the kernel ones have been filled > in. That set_pgd() will be necessary to move any new entry over. Not really; it should just fall through to the pmd "level", which as emulated should do all the instantiation needed for non-PAE. On Wed, Apr 30, 2003 at 08:39:04PM -0700, Dave Hansen wrote: > - a process does a vmalloc, which eventually calls pte_alloc_kernel() > - pte_alloc_kernel() is always called with init_mm as its mm argument > - pte_alloc_kernel() populates init_mm PGD entries with the new pte page > - the process goes to use its new vmalloc'd area, and faults, because > its pgd doesn't have the same entries. do_page_fault():vmalloc_fault > brings over the necessary entries from init, and the fault is handled Sounds like a good plan to me. On Wed, Apr 30, 2003 at 08:39:04PM -0700, Dave Hansen wrote: > The other option is to hold mmlist_lock and populate the entries around > when pte_alloc_kernel() is called. The lazy way is better because not > every process will go looking into the vmalloc area, _and_ and new pgds > should be copied from the init one anyway, and inherit the PTE mapping. > The lazy update only needs to be done for processes when their PGDs > were allocated in the past. Yeah, that could get ugly. Best to keep things lazy. -- wli -- 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