Re: [three fio patches 3/3] smalloc: allocate pool-> members from shared memory

[Jens Axboe <axboe@kernel.dk>]

On 8/28/19 11:48 AM, vincentfu@gmail.com wrote:
> From: Vincent Fu <vincent.fu@wdc.com>
> 
> If one process is making smalloc calls and another process is making
> sfree calls, pool->free_blocks and pool->next_non_full will not be
> synchronized because the two processes each have independent, local
> copies of the variables.
> 
> This patch allocates space for the two variables from shared storage so
> that separate processes will be modifying quantities stored at the same
> locations.
> 
> This issue was discovered on the server side running a client/server job
> with --status-interval=1. Such a job encountered an OOM error when only
> ~50 objects were allocated from the smalloc pool.
> 
> Also change the calculation of free_blocks in add_pool() to use
> SMALLOC_BPI instead of SMALLOC_BPB. These two constants are
> coincidentally the same on Linux and Windows but SMALLOC_BPI is the
> correct one to use. free_blocks is the number of available blocks of
> size SMALLOC_BPB. It is the product of the number of unsigned integers
> in the bitmap (bitmap_blocks) and the number of bits per unsigned
> integer (SMALLOC_BPI).

Would it make more sense to just have the pool[] come out of shared
memory?

-- 
Jens Axboe