Messages in this thread | | | From | Andi Kleen <> | Subject | Re: Preemptable Ticket Spinlock | Date | Mon, 22 Apr 2013 14:56:44 -0700 |
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Rik van Riel <riel@redhat.com> writes: > > If we always incremented the ticket number by 2 (instead of 1), then > we could use the lower bit of the ticket number as the spinlock.
Spinning on a single bit is very inefficient, as you need to do try lock in a loop which is very unfriendly to the MESI state protocol. It's much better to have at least three states and allow spinning-while-reading-only.
This is typically very visible on systems with >2S.
-Andi
-- ak@linux.intel.com -- Speaking for myself only
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