Messages in this thread | | | Date | Mon, 09 Jul 2007 17:39:59 +1000 | From | Nick Piggin <> | Subject | Re: [RFC/PATCH] Use mmu_gather for fork() instead of flush_tlb_mm() |
| |
Benjamin Herrenschmidt wrote: > Use mmu_gather for fork() instead of flush_tlb_mm() > > This patch uses an mmu_gather for copying page tables instead of > flush_tlb_mm(). This allows archs like ppc32 with hash table to > avoid walking the page tables a second time to invalidate hash > entries, and to only flush PTEs that have actually been changed > from RW to RO. > > Note that this contain a small change to the mmu gather stuff, > it must not call free_pages_and_swap_cache() if no page have been > queued up for freeing (if we are only invalidating PTEs). Calling > it on fork can deadlock (I haven't dug why but it looks like a > good idea to test anyway if we're going to use the mmu_gather for > more than just removing pages). > > If the patch gets accepted, I will split that bit from the rest > of the patch and send it separately. > > The main possible issue I see is with huge pages. Arch code might > have relied on flush_tlb_mm() and might not cope with > tlb_remove_tlb_entry() called for huge PTEs. > > Other possible issues are if archs make assumptions about > flush_tlb_mm() being called in fork for different unrelated reasons. > > Ah also, we could probably improve the tracking of start/end, in > the case of lock breaking, the outside function will still finish > the batch with the entire range. It doesn't matter on ppc and x86 > I think though.
Would it be better off to start off with a new API for this? The mmu gather I think is traditionally entirely for dealing with page removal...
-- SUSE Labs, Novell Inc. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |