Messages in this thread | | | Subject | Re: Active Memory Defragmentation: Our implementation & problems | From | Dave Hansen <> | Date | 04 Feb 2004 11:56:33 -0800 |
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On Wed, 2004-02-04 at 10:54, Alok Mooley wrote: > --- Dave Hansen <haveblue@us.ibm.com> wrote: > > > The "work until we get interrupted and restart if > > something changes > > state" approach is very, very common. Can you give > > some more examples > > of just how a page fault would ruin the defrag > > process? > > > > What I mean to say is that if we have identified some > pages for movement, & we get preempted, the pages > identified as movable may not remain movable any more > when we are rescheduled. We are left with the task of > identifying new movable pages.
Depending on the quantity of work that you're trying to do at once, this might be unavoidable.
I know it's a difficult thing to think about, but I still don't understand the precise cases that you're concerned about. Page faults to me seem like the least of your problems. A bigger issue would be if the page is written to by userspace after you copy, but before you install the new pte. Did I miss the code in your patch that invalidated the old tlb entries?
--dave
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