Messages in this thread | | | Date | Fri, 08 Oct 2010 09:24:32 -0400 | From | Rik van Riel <> | Subject | Re: [PATCH 2/3] Retry page fault when blocking on disk transfer. |
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On 10/08/2010 12:39 AM, Michel Lespinasse wrote: > On Tue, Oct 05, 2010 at 03:44:22PM -0700, Michel Lespinasse wrote: >> On Tue, Oct 5, 2010 at 10:38 AM, Rik van Riel<riel@redhat.com> wrote: >>> Looks like it should be relatively easy to do something >>> similar in do_swap_page also. >> >> Good idea. We don't make use of swap too much, which is probably why >> we didn't have that in our kernel, but it seems like a good idea just >> for uniformity. I'll add this in a follow-on patch. > > So here's the patch. Sorry for the delay - it did not take long to write, > but I couldn't test it before today. > > Please have a look - I'd like to add this to the series I sent earlier. > > ----------------------------------- 8< --------------------------------- > > Retry page fault when blocking on swap in > > This change is the cousin of 'Retry page fault when blocking > on disk transfer'. The idea here is to reduce mmap_sem hold times > that are caused by disk transfers when swapping in pages. We drop > mmap_sem while waiting for the page lock, and return the VM_FAULT_RETRY > flag. do_page_fault will then re-acquire mmap_sem and retry the > page fault. It is expected that upon retry the page will now be cached, > and thus the retry will complete with a low mmap_sem hold time. > > Signed-off-by: Michel Lespinasse<walken@google.com> > > diff --git a/mm/memory.c b/mm/memory.c > index b068c68..0ec70b4 100644 > --- a/mm/memory.c > +++ b/mm/memory.c > @@ -2613,6 +2613,21 @@ int vmtruncate_range(struct inode *inode, loff_t offset, loff_t end) > return 0; > } > > +static inline int lock_page_or_retry(struct page *page, struct mm_struct *mm, > + unsigned int flags) > +{ > + if (trylock_page(page)) > + return 1; > + if (!(flags& FAULT_FLAG_ALLOW_RETRY)) { > + __lock_page(page); > + return 1; > + } > + > + up_read(&mm->mmap_sem); > + wait_on_page_locked(page); > + return 0; > +}
Wait a moment. Your other patch 2/3 also has a lock_page_or_retry function. That one is in filemap.c and takes slightly different arguments, to do essentially the same thing...
+/* + * Lock the page, unless this would block and the caller indicated that it + * can handle a retry. + */ +static int lock_page_or_retry(struct page *page, + struct vm_area_struct *vma, struct vm_fault *vmf) +{
Is there a way the two functions can be merged into one?
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