Messages in this thread | | | Date | Fri, 21 Dec 2012 18:22:10 -0800 | From | Tejun Heo <> | Subject | Re: [PATCH 25/25] ipc: don't use [delayed_]work_pending() |
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Hello, Andrew.
On Fri, Dec 21, 2012 at 06:15:23PM -0800, Andrew Morton wrote: > On Fri, 21 Dec 2012 17:57:15 -0800 Tejun Heo <tj@kernel.org> wrote: > > > There's no need to test whether a (delayed) work item in pending > > before queueing, flushing or cancelling it. Most uses are unnecessary > > and quite a few of them are buggy. > > > - if (!work_pending(&ipc_memory_wq)) > > - schedule_work(&ipc_memory_wq); > > + schedule_work(&ipc_memory_wq); > > Well, the new code is a ton slower than the old code if the work is > frequently pending, so some care is needed with such a conversion.
Yeah, I mentioned it in the head message. it comes down to test_and_set_bit() vs. test_bit() and none of the current users seems to be hot enough for that to matter at all.
In very hot paths, such optimization *could* be valid. The problem is that [delayed_]work_pending() seem to be abused much more than they are put to any actual usefulness. Maybe we should rename them to something really ugly. I don't know.
> That's not an issue for the IPC callsite - memory offlining isn't > frequent. > > > ... > > > > Please let me know how this patch should be routed. I can take it > > through the workqueue tree if necessary. > > > > Please merge this one yourself.
Can I add your acked-by?
Thanks.
-- tejun
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