Re: [PATCH V5,net-next] net: mana: Add page pool for RX buffers

[Jesper Dangaard Brouer]

On 03/08/2023 03.44, Jesse Brandeburg wrote:
> On 8/2/2023 11:07 AM, Haiyang Zhang wrote:
> > Add page pool for RX buffers for faster buffer cycle and reduce CPU
> > usage.

Can you add some info on the performance improvement this patch gives?

Your previous post mentioned:
> With iperf and 128 threads test, this patch improved the throughput 
by 12-15%, and decreased the IRQ associated CPU's usage from 99-100% to 
10-50%.


> > The standard page pool API is used.
> >
> > Signed-off-by: Haiyang Zhang <haiyangz@xxxxxxxxxxxxx>
> > ---
> > V5:
> > In err path, set page_pool_put_full_page(..., false) as suggested by
> > Jakub Kicinski
> > V4:
> > Add nid setting, remove page_pool_nid_changed(), as suggested by
> > Jesper Dangaard Brouer
> > V3:
> > Update xdp mem model, pool param, alloc as suggested by Jakub Kicinski
> > V2:
> > Use the standard page pool API as suggested by Jesper Dangaard Brouer
> > ---
>
> > diff --git a/include/net/mana/mana.h b/include/net/mana/mana.h
> > index 024ad8ddb27e..b12859511839 100644
> > --- a/include/net/mana/mana.h
> > +++ b/include/net/mana/mana.h
> > @@ -280,6 +280,7 @@ struct mana_recv_buf_oob {
> >   	struct gdma_wqe_request wqe_req;
> >   
> >   	void *buf_va;
> > +	bool from_pool; /* allocated from a page pool */
>
> suggest you use flags and not bools, as bools waste 7 bits each, plus
> your packing of this struct will be full of holes, made worse by this
> patch. (see pahole tool)

Agreed.

> >   
> >   	/* SGL of the buffer going to be sent has part of the work request. */
> >   	u32 num_sge;
> > @@ -330,6 +331,8 @@ struct mana_rxq {
> >   	bool xdp_flush;
> >   	int xdp_rc; /* XDP redirect return code */
> >   
> > +	struct page_pool *page_pool;
> > +
> >   	/* MUST BE THE LAST MEMBER:
> >   	 * Each receive buffer has an associated mana_recv_buf_oob.
> >   	 */
>
>
> The rest of the patch looks ok and is remarkably compact for a
> conversion to page pool. I'd prefer someone with more page pool exposure
> review this for correctness, but FWIW
>

Both Jakub and I have reviewed the page_pool parts, and I think we are
in a good place.

Looking at the driver, I wonder why you are keeping the driver local
memory cache (when PP is also contains a memory cache) ?
(I assume there is a good reason, so this is not blocking patch)

> Reviewed-by: Jesse Brandeburg <jesse.brandeburg@xxxxxxxxx>

Thanks for taking your time to review.

I'm ready to ACK once the description is improved a bit :-)

--Jesper
pw-bot: cr