> On Tue, 13 Mar 2007 23:01:11 +1100 Nick Piggin <[EMAIL PROTECTED]> wrote: > Andrew Morton wrote: > >>On Tue, 13 Mar 2007 22:30:19 +1100 Nick Piggin <[EMAIL PROTECTED]> wrote: > >>We don't actually have to zap_pte_range the entire page table in > >>order to free it (IIRC we used to have to, before the 4lpt patches). > > > > > > I'm trying to remember why we ever would have needed to zero out the > > pagetable > > pages if we're taking down the whole mm? Maybe it's because "oh, the > > arch wants to put this page into a quicklist to recycle it", which is > > all rather circular. > > > > It would be interesting to look at a) leave the page full of random garbage > > if we're releasing the whole mm and b) return it straight to the page > > allocator. > > Well we have the 'fullmm' case, which avoids all the locked pte operations > (for those architectures where hardware pt walking requires atomicity).
I suspect there are some tlb operations which could be skipped in that case too. > However we still have to visit those to-be-unmapped parts of the page table > to find the pages and free them. So we still at least need to bring it into > cache for the read... at which point, the store probably isn't a big burden. It means all that data has to be written back. Yes, I expect it'll prove to be less costly than the initial load. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
