Messages in this thread | | | Date | Sun, 11 May 2008 16:42:03 +0200 | From | Ingo Molnar <> | Subject | Re: [git pull] scheduler fixes |
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* Matthew Wilcox <matthew@wil.cx> wrote:
> > > Current XFS CVS has a fix from myself and Christoph that gets rid > > > of the l_flushsema and replaces it with a staggered wakeup of each > > > task that's waiting as the previously woken task clears the > > > critical section. > > > > the solution is to reduce semaphore usage by converting them to > > mutexes. Is anyone working on removing legacy semaphore use from > > XFS? > > This race is completely irrelevant to converting semaphores to > mutexes. [...]
i was not talking about the race. I was just reacting on your comments about thundering herds and staggered wakeups - which is a performance detail. Semaphores should not regress AIM7 by 50% but otherwise they are legacy code and their use should be reduced monotonically, so i was asking why anyone still cares about tuning semaphore details in XFS instead of just working on removing semaphore use from them.
> [...] It can only occur for semaphores which /can't/ be converted to > mutexes.
exactly what usecase is that? Perhaps it could be converted to an atomic counter + the wait_event() APIs.
Ingo
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