Re: [PATCH v3] benchtests: Add malloc microbenchmark

[OndÅej BÃlka <neleai at seznam dot cz>]

On Thu, Jun 19, 2014 at 05:46:08PM +0100, Will Newton wrote:
> Add a microbenchmark for measuring malloc and free performance with
> varying numbers of threads. The benchmark allocates and frees buffers
> of random sizes in a random order and measures the overall execution
> time and RSS. Variants of the benchmark are run with 1, 4, 8 and
> 16 threads.
> 
> The random block sizes used follow an inverse square distribution
> which is intended to mimic the behaviour of real applications which
> tend to allocate many more small blocks than large ones.
> 
> ChangeLog:
> 
> 2014-06-19  Will Newton  <will.newton@linaro.org>
> 
> 	* benchtests/Makefile: (bench-malloc): Add malloc thread
> 	scalability benchmark.
> 	* benchtests/bench-malloc-threads.c: New file.
> ---
>  benchtests/Makefile              |  20 ++-
>  benchtests/bench-malloc-thread.c | 299 +++++++++++++++++++++++++++++++++++++++
>  2 files changed, 316 insertions(+), 3 deletions(-)
>  create mode 100644 benchtests/bench-malloc-thread.c
> 
> Changes in v3:
>  - Single executable that takes a parameter for thread count
>  - Run for a fixed duration rather than a fixed number of loops
>  - Other fixes in response to review suggestions
> 
> Example of a plot of the results versus tcmalloc and jemalloc on
> a 4 core i5:
> 
> http://people.linaro.org/~will.newton/bench-malloc-threads.png
> 
That graph looks interesting. It is little weird that in libc a 2 and
three thread take nearly same time but not when you use four thread one.

For other allocators a dependency is linear. How could you explain that?