Re: LSFMMBPF proposal [MM]: Eliminate vmap/vmalloc lock contention

[Uladzislau Rezki <urezki@gmail.com>]

>
> Hello, LSF.
>
> Title: Introduce a per-cpu-vmap-cache to eliminate a vmap lock contention
>
> Description:
>  Currently the vmap code is not scaled to number of CPU cores in a system
>  because a global vmap space is protected by a single spinlock. Such approach
>  has a clear bottleneck if many CPUs simultaneously access to one resource.
>
>  In this talk i would like to describe a drawback, show some data related
>  to contentions and places where those occur in a code. Apart of that i
>  would like to share ideas how to eliminate it providing a few approaches
>  and compare them.
>
> Requirements:
>  * It should be a per-cpu approach;
>  * Search of freed ptrs should not interfere with other freeing(as much as we can);
>  *   - offload allocated areas(buzy ones) per-cpu;
>  * Cache ready sized objects or merge them into one big per-cpu-space(split on demand);
>  * Lazily-freed areas either drained per-cpu individually or by one CPU for all;
>  * Prefetch a fixed size in front and allocate per-cpu
>
> Goals:
>  * Implement a per-cpu way of allocation to eliminate a contention.
>
Thank you for giving a time to talk about this topic on the LSFMMBPF.
The slides can
be accessed here:

wget ftp://vps418301.ovh.net/incoming/Mitigate_a_vmalloc_lock_contention_in_SMP_env_v1.pdf

There were some issues with a camera, but i was told in the end you
could see me.2

Thank you again!

-- 
Uladzislau Rezki