Re: [Boost-users] Thread local storage

Subject: Re: [Boost-users] Thread local storage
From: Peter Dimov (pdimov_at_[hidden])
Date: 2009-03-29 17:54:13

Oliver Abert:
> 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.

It looks like Mac OS's pthread_once is slower than the one in Linux. Can you 
provide further clues about the call stack? Where does the pthread_once call 
come from? This might help Anthony Williams (the maintainer of Boost.Thread) 
fix the performance problem by somehow avoiding the particular pthread_once 
call.