Messages in this thread | | | Subject | Re: [RFC] Event counters [1/3]: Basic counter functionality | From | Nick Piggin <> | Date | Tue, 03 Jan 2006 16:11:46 +1100 |
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On Mon, 2006-01-02 at 19:40 -0200, Marcelo Tosatti wrote:
> Nick, > > The following patch: > > - Moves the lightweight "inc/dec" versions of mod_page_state variants > to three underscores, making those the default for locations where enough > locks are held. >
I guess I was hoping to try to keep it simple, and just have two variants, the __ version would require the caller to do the locking. In cases like eg. allocstall, they should happen infrequently enough that the extra complexity is probably not worth worrying about.
I don't think I commented about the preempt race though (and requirement to have preempt off from process context), which obviously can be a problem as you say (though I think things are currently safe?).
> - Make the two-underscore version disable and enable preemption, which > is required to avoid preempt-related races which can result in missed > updates. > > - Extends the lightweight version usage in page reclaim, > pte allocation, and a few other codepaths. >
I guess nr_dirty looks OK in the places it can be put under tree_lock.
nr_page_table_pages is OK because ptl should be held to prevent preempt.
pgrotated and pgactivate should be good because of lru_lock.
Thanks for going through these!
-- SUSE Labs, Novell Inc.
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