Messages in this thread | | | Date | Tue, 18 Apr 2006 01:27:40 -0700 (PDT) | From | Christoph Lameter <> | Subject | Re: [PATCH 5/5] Swapless V2: Revise main migration logic |
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On Tue, 18 Apr 2006, KAMEZAWA Hiroyuki wrote:
> On Mon, 17 Apr 2006 23:58:41 -0700 (PDT) > Christoph Lameter <clameter@sgi.com> wrote: > > > Hmmm... Good ideas. I think it could be much simpler like the following > > patch. > > > > However, the problem here is how to know that we really took the anon_vma > > lock and what to do about a page being unmmapped while migrating. This > > could cause the anon_vma not to be unlocked. > > > lock dependency here is page_lock(page) -> page's anon_vma->lock. > So, I guess anon_vma->lock cannot be unlocked by other threads > if we have page_lock(page).
No the problem is to know if the lock was really taken. SWAP_AGAIN could mean that page_lock_anon_vma failed.
Also the page may be freed while it is being processes. In that case remove_migration_ptes may not find the mapping and may not unlock the anon_vma.
> > I guess we would need to have try_to_unmap return some state information. > What kind of information ?
Information that indicates that the anon_vma lock was taken.
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