[SPDK] A question for bdev_io cache

[Yijing Wang <wangyijing0307 at gmail.com>]

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Hi James,

      I'm a spdk developer from china, I'm sorry to disturb you, 
recently I read the latest spdk bdev io code, and found that spdk 
prepopulate per-thread bdev_io cache in bdev module.

As we knew, dpdk rte_mempool_create has a parameter cache_size which 
allow users to cache some objects in local cpu,  my question is why you 
post the patch to create bdev io cache

in bdev own list, but not use default dpdk rte_mempool cache mechnasim？ 
The reason is dpdk rte_mempool cache cannot prevent a bdev device in a 
thread from starvation? Since dpdk

rte_mempool cache is preserved for all users in the same cpu thread.


Thanks!

Yijing.