We need measurements for a few other loads I think.
> > For this to work, anon pages will need to have something in page->index.
> > This isn't too much of a challenge. A reasonable value to put in there is
> > the creator's virtual address, shifted right, and perhaps mangled a little to
> > reduce contention.
> Well you want the likely-to-be-temporally-adjacent anon pages to
> use the same lock. So maybe
> page->index = some_global_int++;
Yes, that's better.
> Except ->index gets stomped on when the page gets added to swapcache.
> Which means that the address of its lock will change. I can't immediately
> think of a fix for that.
We'd have to hold the lock while changing the page->index. Pte_chain_lock
would additionally have to check the page->index after acquiring the lock
and, if changed, drop it and take the new one. I don't think the overhead
for this check is significant.
Add_to_page_cache would want new flavor that shortens up the pte chain lock
hold time, but it looks like it should have a swap-specific variant anyway.
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