Re: [Sbcl-devel] [Patch] Faster mutex.

[Marco M. <ma...@ac...>]

I forgot to mention that the algorithm was stolen from the paper "Futex 
Are Tricky", by Ulrich  Drepper. You can see an explanation there. But 
with the comments I added I think it is easier to see what is going on.

Marco

Juho Snellman wrote:
> Marco Monteiro <ma...@ac...> writes:
>> As currently implemented, release-mutex makes a system call even if
>> there is no contention for the mutex. This patch corrects that.
> [...]
>> In my system, with an uncontended mutex, RELEASE-MUTEX is more than
>> 30x faster with the patch.
>>
>> I tested the patch in a x86-64 machine running Linux. I created VOPs
>> for x86 but I did not test this.
>>
>> Please review and apply.
> 
> Thanks. A few issues:
> 
>   * It's not immediately obvious that the code is correct. Could you add
>     some comments that explain what is going on, and why it's correct?
>   * The mutex structure now has fields named VAL and VALUE, which isn't
>     very clear. VAL should probably be renamed to something more descriptive.
>     Maybe STATE?
>   * There are lots of magic numbers in the code. They should probably
>     be named.  
> 
>> The new VOPs will be reworked in a future patch.
> 
> In what way?
>