Messages in this thread | | | Date | Sat, 7 Mar 2015 09:09:27 -0500 | From | Jeff Layton <> | Subject | Re: [PATCH v3 0/2] Use blocked_lock_lock only to protect blocked_hash |
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On Sat, 7 Mar 2015 09:00:41 -0500 Jeff Layton <jlayton@poochiereds.net> wrote:
> On Fri, 6 Mar 2015 08:53:30 +0100 > Daniel Wagner <daniel.wagner@bmw-carit.de> wrote: > > > Hi, > > > > Finally, I got a bigger machine and did a quick test round. I expected > > to see some improvements but the resutls do not show any real gain. So > > they are merely refactoring patches. > > > > Ok, in that case is there any point in merging these? I'm all for > breaking up global locks when it makes sense, but if you can't > demonstrate a clear benefit then I'm less inclined to take the churn. > > Perhaps we should wait to see if a benefit emerges when/if you convert > the lglock code to use normal spinlocks (like Andi suggested)? That > seems like a rather simple conversion, and I don't think it's > "cheating" in any sense of the word. > > I do however wonder why Nick used arch_spinlock_t there when he wrote > the lglock code instead of normal spinlocks. Was it simply memory usage > considerations or something else? >
Hmm...to answer my own question. The (old) LWN article here seems to suggest that he did it that way to avoid preemption:
http://lwn.net/Articles/401738/
I don't think we need to avoid being preempted in the file-locking code, but I'm not sure about stop_machine.c. Is that necessary there? The comment in queue_stop_cpus_work seems to indicate that it may be.
-- Jeff Layton <jlayton@poochiereds.net>
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