Re: [PATCH v5 1/3] mempool: support external handler

[Jerin Jacob <jerin.jacob@caviumnetworks.com>]

On Fri, May 27, 2016 at 03:44:31PM +0100, Hunt, David wrote:
> 
> 
Hi David,
[snip]
>      That chunk of code above would be better moved all right. I'd suggest
> moving it to the
> rte_mempool_create function, as that's the one that needs the backward
> compatibility.

OK

> 
> On the flags issue, each mempool handler can re-interpret the flags as
> needed. Maybe we
> could use the upper half of the bits for different handlers, changing the
> meaning of the
> bits depending on which handler is being set up. We can then keep the lower
> half for bits that are common across all handlers? That way the user can

Common lower half bit in flags looks good.

> just set the bits they
> are interested in for that handler. Also, the alloc function has access to
> the flags, so maybe the
> handler specific setup could be handled in the alloc function rather than
> adding a new function pointer?

Yes. I agree.

> 
> Of course, that won't help if we need to pass in more data, in which case
> we'd probably need an
> opaque data pointer somewhere. It would probably be most useful to pass it
> in with the
> alloc, which may need the data. Any suggestions?

But the top level rte_mempool_create() function needs to pass the data. Right?
That would be an ABI change. IMO, we need to start thinking about
passing a struct of config data to rte_mempool_create to create
backward compatibility on new argument addition to rte_mempool_create()

Other points in HW assisted pool manager perspective,

1) May be RING can be replaced with some other higher abstraction name
for the internal MEMPOOL_F_RING_CREATED flag
2) IMO, It is better to change void *pool in struct rte_mempool to
anonymous union type, something like below, so that mempool
implementation can choose the best type.
	union {
		void *pool;
		uint64_t val;
	}

3) int32_t handler_idx creates 4 byte hole in struct rte_mempool in
64 bit system. IMO it better to rearrange.(as const struct rte_memzone
*mz comes next)

4) IMO, It is better to change ext_alloc/ext_free to ext_create/ext_destroy
as their is no allocation in HW assisted pool manager case,
it will be mostly creating some HW initialization.

> 
> Regards,
> Dave.
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