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[Bug translator/11695] DWIM promotion of ++ to <<<
- From: "jistone at redhat dot com" <sourceware-bugzilla at sourceware dot org>
- To: systemtap at sources dot redhat dot com
- Date: 11 Jun 2010 15:52:45 -0000
- Subject: [Bug translator/11695] DWIM promotion of ++ to <<<
- References: <20100611141707.11695.fche@redhat.com>
- Reply-to: sourceware-bugzilla at sourceware dot org
------- Additional Comments From jistone at redhat dot com 2010-06-11 15:52 -------
(In reply to comment #1)
> The aggregate doesn't need a global lock, it uses per-cpu counters.
It does have a lock, but the exclusiveness is inverted: <<< takes a read lock
and @extract takes a write lock. You can think of it as locking the aggregate
structure, which you write to when @extracting data from the per-cpu structures.
So this transformation is only worthwhile when updating the value is more common
than reading it.
--
http://sourceware.org/bugzilla/show_bug.cgi?id=11695
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