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Date:   Tue, 9 May 2023 10:30:34 +0300
From:   Leon Romanovsky <leon@kernel.org>
To:     Haiyang Zhang <haiyangz@microsoft.com>
Cc:     Long Li <longli@microsoft.com>, Jason Gunthorpe <jgg@ziepe.ca>,
        Ajay Sharma <sharmaajay@microsoft.com>,
        Dexuan Cui <decui@microsoft.com>,
        KY Srinivasan <kys@microsoft.com>,
        Wei Liu <wei.liu@kernel.org>,
        "David S. Miller" <davem@davemloft.net>,
        Eric Dumazet <edumazet@google.com>,
        Jakub Kicinski <kuba@kernel.org>,
        Paolo Abeni <pabeni@redhat.com>,
        "linux-rdma@vger.kernel.org" <linux-rdma@vger.kernel.org>,
        "linux-hyperv@vger.kernel.org" <linux-hyperv@vger.kernel.org>,
        "netdev@vger.kernel.org" <netdev@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] RDMA/mana_ib: Use v2 version of cfg_rx_steer_req to
 enable RX coalescing
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On Mon, May 08, 2023 at 02:45:44PM +0000, Haiyang Zhang wrote:
> 
> 
> > -----Original Message-----
> > From: Leon Romanovsky <leon@kernel.org>
> > Sent: Monday, May 8, 2023 2:10 AM
> > To: Haiyang Zhang <haiyangz@microsoft.com>
> > Cc: Long Li <longli@microsoft.com>; Jason Gunthorpe <jgg@ziepe.ca>; Ajay
> > Sharma <sharmaajay@microsoft.com>; Dexuan Cui <decui@microsoft.com>;
> > KY Srinivasan <kys@microsoft.com>; Wei Liu <wei.liu@kernel.org>; David S.
> > Miller <davem@davemloft.net>; Eric Dumazet <edumazet@google.com>;
> > Jakub Kicinski <kuba@kernel.org>; Paolo Abeni <pabeni@redhat.com>; linux-
> > rdma@vger.kernel.org; linux-hyperv@vger.kernel.org;
> > netdev@vger.kernel.org; linux-kernel@vger.kernel.org
> > Subject: Re: [PATCH] RDMA/mana_ib: Use v2 version of cfg_rx_steer_req to
> > enable RX coalescing
> > 
> > On Sun, May 07, 2023 at 09:39:27PM +0000, Haiyang Zhang wrote:
> > >
> > >
> > > > -----Original Message-----
> > > > From: Leon Romanovsky <leon@kernel.org>
> > > > Sent: Sunday, May 7, 2023 4:11 AM
> > > > To: Long Li <longli@microsoft.com>
> > > > Cc: Jason Gunthorpe <jgg@ziepe.ca>; Ajay Sharma
> > > > <sharmaajay@microsoft.com>; Dexuan Cui <decui@microsoft.com>; KY
> > > > Srinivasan <kys@microsoft.com>; Haiyang Zhang
> > <haiyangz@microsoft.com>;
> > > > Wei Liu <wei.liu@kernel.org>; David S. Miller <davem@davemloft.net>; Eric
> > > > Dumazet <edumazet@google.com>; Jakub Kicinski <kuba@kernel.org>;
> > Paolo
> > > > Abeni <pabeni@redhat.com>; linux-rdma@vger.kernel.org; linux-
> > > > hyperv@vger.kernel.org; netdev@vger.kernel.org; linux-
> > > > kernel@vger.kernel.org
> > > > Subject: Re: [PATCH] RDMA/mana_ib: Use v2 version of cfg_rx_steer_req
> > to
> > > > enable RX coalescing
> > > >
> > > > On Fri, May 05, 2023 at 11:51:48AM -0700, longli@linuxonhyperv.com
> > > > wrote:
> > > > > From: Long Li <longli@microsoft.com>
> > > > >
> > > > > With RX coalescing, one CQE entry can be used to indicate multiple
> > packets
> > > > > on the receive queue. This saves processing time and PCI bandwidth over
> > > > > the CQ.
> > > > >
> > > > > Signed-off-by: Long Li <longli@microsoft.com>
> > > > > ---
> > > > >  drivers/infiniband/hw/mana/qp.c |  5 ++++-
> > > > >  include/net/mana/mana.h         | 17 +++++++++++++++++
> > > > >  2 files changed, 21 insertions(+), 1 deletion(-)
> > > >
> > > > Why didn't you change mana_cfg_vport_steering() too?
> > >
> > > The mana_cfg_vport_steering() is for mana_en (Enthernet) driver, not the
> > > mana_ib driver.
> > >
> > > The changes for mana_en will be done in a separate patch together with
> > > changes for mana_en RX code patch to support multiple packets / CQE.
> > 
> > I'm aware of the difference between mana_en and mana_ib.
> > 
> > The change you proposed doesn't depend on "support multiple packets /
> > CQE."
> > and works perfectly with one packet/CQE also, does it?
> 
> No.
> If we add the following setting to the mana_en / mana_cfg_vport_steering(),
> the NIC may put multiple packets in one CQE, so we need to have the changes
> for mana_en RX code path to support multiple packets / CQE.
> +	req->cqe_coalescing_enable = true;

You can leave "cqe_coalescing_enable = false" for ETH and still reuse
your new v2 struct.

H> 
> So we plan to set this cqe_coalescing_enable, and the changes for mana_en 
> RX code path to support multiple packets / CQE in another patch.

And how does it work with IB without changing anything except this
proposed patch?

Thanks

> 
> Thanks,
> - Haiyang
>