Re: [Boost-users] Thread local storage

Subject: Re: [Boost-users] Thread local storage
From: Anthony Williams (anthony.ajw_at_[hidden])
Date: 2009-03-30 03:47:58

Thanks for alerting me to this thread Peter.

Oliver Abert <abert_at_[hidden]> writes:

> On 29.03.2009, at 19:36, Peter Dimov wrote:
>
>> Oliver Abert:
>>> Hi Everyone,
>>>
>>> I am using Boost Threads (1.38) as threading library and I also use
>>> the thread_specific_ptr to store a minor amount of data per  thread
>>> (I  think currently it is like 5 different pointer values  per
>>> thread).  Technically everything works out fine, but I am  having a
>>> performance  problem on Mac OS X. On Linux the performance  is 10
>>> times faster than  on Mac OS. If I use pthreads on Mac OS I  have
>>> identical performance to  the Linux version. Both versions are
>>> running on the same machine using  8 threads both.
>>
>> What does your profiler say?
>
> about 80% of the time is spend in __spin_lock which in turnwas called
> by pthread_once. If I use only one thread (instead of 8) the
> percantage goes down to 2.5% - which is still a bit much for my taste.

pthread_once is called by the thread_specific_ptr code to ensure that
the TLS key it uses has been allocated and is valid. It's a real pain if
that is too slow.

Anthony
-- 
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