Re: [PATCH 4/4] workqueue: slash half memory usage in 32bit system

[Tejun Heo]

On Mon, Jun 01, 2020 at 08:44:42AM +0000, Lai Jiangshan wrote:
> The major memory ussage in workqueue is on the pool_workqueue.
> The pool_workqueue has alignment requirement which often leads
> to padding.
> 
> Reducing the memory usage for the pool_workqueue is valuable.
> 
> And 32bit system often has less memory, less workqueues,
> less works, less concurrent flush_workqueue()s, so we can
> slash the flush color on 32bit system to reduce memory usage
> 
> Before patch:
> The sizeof the struct pool_workqueue is 256 bytes,
> only 136 bytes is in use in 32bit system
> 
> After patch:
> The sizeof the struct pool_workqueue is 128 bytes,
> only 104 bytes is in use in 32bit system, there is still
> room for future usage.
> 
> Setting WORK_STRUCT_COLOR_BITS to 3 can't reduce the sizeof
> the struct pool_workqueue in 64bit system, unless combined
> with big refactor for unbound pwq.

Have you calculated how much memory is actually saved this way on a typical
system?

Thanks.

-- 
tejun