Messages in this thread | | | Date | Mon, 27 Jun 2005 18:22:54 -0700 | From | William Lee Irwin III <> | Subject | Re: [patch 2] mm: speculative get_page |
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William Lee Irwin III wrote: >> SetPageFreeing is only done in shrink_list(), so other pages in the >> buddy bitmaps and/or pagecache pages freed by other methods may not
On Tue, Jun 28, 2005 at 10:03:00AM +1000, Nick Piggin wrote: > It is also done by remove_exclusive_swap_page, although that hunk > leaked into a later patch (#5), sorry. > Other methods (eg truncate) don't seem to have an atomicity guarantee > anyway - ie. it is valid to pick up a reference on a page that is > just about to get truncated. PageFreeing is only used when some code > is making an assumption about the number of users of the page.
tmpfs
William Lee Irwin III wrote: >> be found by this. There's also likely trouble with higher-order pages.
On Tue, Jun 28, 2005 at 10:03:00AM +1000, Nick Piggin wrote: > There isn't because higher order pages aren't used for pagecache.
hugetlbfs
William Lee Irwin III wrote: >> page != *pagep won't be reliably tripped unless the pagecache >> modification has the appropriate memory barriers.
On Tue, Jun 28, 2005 at 10:03:00AM +1000, Nick Piggin wrote: > There are appropriate memory barriers: the radix tree is > modified uner the rwlock/spinlock, and this function has > a memory barrier before testing page != *pagep.
Someone else deal with this (paulus? anton? other arch maintainers?).
William Lee Irwin III wrote: >> The lockless radix tree lookups are a harder problem than this, and >> the implementation didn't look promising. I have other problems to deal >> with so I'm not going to go very far into this.
On Tue, Jun 28, 2005 at 10:03:00AM +1000, Nick Piggin wrote: > What's wrong with the lockless radix tree lookups?
The above is as much as I wanted to go into it. I need to direct my capacity for the grunt work of devising adversary arguments elsewhere.
William Lee Irwin III wrote: >> While I agree that locklessness is the right direction for the >> pagecache to go, this RFC seems to have too far to go to use it to >> conclude anything about the subject.
On Tue, Jun 28, 2005 at 10:03:00AM +1000, Nick Piggin wrote: > You don't seem to have looked enough to conclude anything about it.
You requested comments. I made some.
Anyhow, my review has not been comprehensive. I stopped after the first few things I found that needed fixing. If others could deal with the rest of this, I'd be much obliged.
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