On Tue, 3 Feb 2009 11:55:40 +0900 KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> wrote: > On Tue, 3 Feb 2009 03:31:47 +0100 > Andrea Arcangeli <aarcange@xxxxxxxxxx> wrote: > > > On Tue, Feb 03, 2009 at 10:29:20AM +0900, KAMEZAWA Hiroyuki wrote: > > > On Mon, 2 Feb 2009 23:08:56 +0100 > > > Andrea Arcangeli <aarcange@xxxxxxxxxx> wrote: > > > > > > > Hi Greg! > > > > > > > > > Thanks for the pointers, I'll go read the thread and follow up there. > > > > > > > > If you also run into this final fix is attached below. Porting to > > > > mainline is a bit hard because of gup-fast... Perhaps we can use mmu > > > > notifiers to fix gup-fast... need to think more about it then I'll > > > > post something. > > > > > > > > Please help testing the below on pre-gup-fast kernels, thanks! > > > > > > > I commented in FJ-Redhat Path but not forwared from unknown reason ;) > > > I comment again. > > > > > > 1. Why TestSetLockPage() is necessary ? > > > It seems not necesary. > > > > To avoid the VM to remove or add the page from/to swapcache and change > > page_count/mapcount from under us. This most certainly wasn't the > > reason of the slowdown (the slowdown were the false positives > > generated by pagevec pinning) and removing it was more intrusive than > > I wanted. > > My point is. > - If TestSetLockPage() failes, force_cow=1. > - If count/mapcount check fails, force_cow=1. > > So, lock_page() here seems meaningless. If you consider lock_page() is important, > just use lock_page() seems better. > I changed my thinking. I understood *lock* is necessary here. But I'm not sure this is enough. > > > 3. Why "follow_page() successfully finds a page" case only ? > > > not necessary to insert SetPageGUP() in following path ? > > > > > > - handle_mm_fault() > > > => do_anonymos/swap/wp_page() > > > or some. > > > > No need to change that either, all we need to know are the pages whose > > count vs mapcount has a discrepancy that could have been caused by > > get_user_pages. So only follow_page has to set it. More precisely > > FOLL_GET|FOLL_WRITE is the only path we care about there. > > > > Assume 3 threads in a process. please ignore this, I'm shame ;( -Kame -- To unsubscribe from this list: send the line "unsubscribe linux-man" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
