lkml.org 
[lkml]   [2012]   [Apr]   [1]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: semaphore and mutex in current Linux kernel (3.2.2)

* Chen, Dennis (SRDC SW) <Dennis1.Chen@amd.com> wrote:

> Documentation/mutex-design.txt:
>
> "- 'struct mutex' is smaller on most architectures: E.g. on x86,
> 'struct semaphore' is 20 bytes, 'struct mutex' is 16 bytes.
> A smaller structure size means less RAM footprint, and better
> CPU-cache utilization."
> ================================================================
>
> Now in my x86-64 32-bit Linux environment, 'struct semaphone'
> is 16 bytes, 'struct mutex' is 20 bytes. So seems the RAM
> footprint advantages are not there...

It got larger due to the adaptive spin-mutex performance
optimization.

> For the performance advantages followed, I don't have the
> ./test-mutex and maybe the testing environment, so haven't the
> 1st hand data for this item...

Well, a way to reproduce that would be to find a lock_mutex
intense workload ('perf top -g', etc.), and then changing back
the underlying mutex to a semaphore, and measure the performance
of the two primitives.

Thanks,

Ingo


\
 
 \ /
  Last update: 2012-04-01 14:23    [W:0.063 / U:14.596 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site