Re: [RFC PATCH 0/5] x86,smp: make ticket spinlock proportionalbackoff w/ auto tuning

From: Michel Lespinasse
Date: Thu Jan 03 2013 - 05:45:49 EST

On Wed, Jan 2, 2013 at 9:15 PM, Rik van Riel <riel@xxxxxxxxxx> wrote:
> The v2 series integrates several ideas from Michel Lespinasse
> and Eric Dumazet, which should result in better throughput and
> nicer behaviour in situations with contention on multiple locks.
> Please let me know if you manage to break this code in any way,
> so I can fix it...

I'm seeing some very weird things on my 3 test machines. Looks like
the spinlock delay sometimes gets crazy, at which point spinlock
performance becomes unbearable and the network driver freaks out.

# ./spinlock_load_test
1 spinlocks: 24159990
2 spinlocks: 12900657
3 spinlocks: 11547771
4 spinlocks: 9113
6 spinlocks: 259
8 spinlocks: 310
12 spinlocks: 283
16 spinlocks:
<seems to be stuck here; meanwhile my serial console fills up with
network driver cries>

Well, I take it as an incitation to pay special attention to this code review :)

Michel "Walken" Lespinasse
A program is never fully debugged until the last user dies.
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