Re: [dpdk-dev] [RFC PATCH 0/6] mempool: add bucket mempool driver

[Olivier MATZ <olivier.matz@6wind.com>]

Hi Andrew,

Please find some comments about this patchset below.
I'll also send some comments as replies to the specific patch.

On Fri, Nov 24, 2017 at 04:06:25PM +0000, Andrew Rybchenko wrote:
> The patch series adds bucket mempool driver which allows to allocate
> (both physically and virtually) contiguous blocks of objects and adds
> mempool API to do it. It is still capable to provide separate objects,
> but it is definitely more heavy-weight than ring/stack drivers.
>
> The target usecase is dequeue in blocks and enqueue separate objects
> back (which are collected in buckets to be dequeued). So, the memory
> pool with bucket driver is created by an application and provided to
> networking PMD receive queue. The choice of bucket driver is done using
> rte_eth_dev_pool_ops_supported(). A PMD that relies upon contiguous
> block allocation should report the bucket driver as the only supported
> and preferred one.

So, you are planning to use this driver for a future/existing PMD?

Do you have numbers about the performance gain, in which conditions,
etc... ? And are there conditions where there is a performance loss ?

> The number of objects in the contiguous block is a function of bucket
> memory size (.config option) and total element size.

The size of the bucket memory is hardcoded to 32KB.
Why this value ?
Won't that be an issue if the user wants to use larger objects?

> As I understand it breaks ABI so it requires 3 acks in accordance with
> policy, deprecation notice and mempool shared library version bump.
> If there is a way to avoid ABI breakage, please, let us know.

If my understanding is correct, the ABI breakage is caused by the
addition of the new block dequeue operation, right?


Thanks
Olivier