-----Original Message-----
From: Jesper Dangaard Brouer <redacted>
Sent: Monday, July 24, 2023 7:29 AM
To: Haiyang Zhang <haiyangz@microsoft.com>; linux-hyperv@vger.kernel.org;
netdev@vger.kernel.org
Cc: brouer@redhat.com; Dexuan Cui <decui@microsoft.com>; KY Srinivasan
[off-list ref]; Paul Rosswurm [off-list ref];
olaf@aepfle.de; vkuznets@redhat.com; davem@davemloft.net;
wei.liu@kernel.org; edumazet@google.com; kuba@kernel.org;
pabeni@redhat.com; leon@kernel.org; Long Li [off-list ref];
ssengar@linux.microsoft.com; linux-rdma@vger.kernel.org;
daniel@iogearbox.net; john.fastabend@gmail.com; bpf@vger.kernel.org;
ast@kernel.org; Ajay Sharma [off-list ref]; hawk@kernel.org;
tglx@linutronix.de; shradhagupta@linux.microsoft.com; linux-
kernel@vger.kernel.org; Ilias Apalodimas [off-list ref]; Jesper
Dangaard Brouer [off-list ref]
Subject: Re: [PATCH V3,net-next] net: mana: Add page pool for RX buffers



On 21/07/2023 21.05, Haiyang Zhang wrote:

quoted

Add page pool for RX buffers for faster buffer cycle and reduce CPU
usage.

The standard page pool API is used.

Signed-off-by: Haiyang Zhang <haiyangz@microsoft.com>
---
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

---
  drivers/net/ethernet/microsoft/mana/mana_en.c | 91 +++++++++++++++----
  include/net/mana/mana.h                       |  3 +
  2 files changed, 78 insertions(+), 16 deletions(-)

diff --git a/drivers/net/ethernet/microsoft/mana/mana_en.c

b/drivers/net/ethernet/microsoft/mana/mana_en.c

quoted

index a499e460594b..4307f25f8c7a 100644

--- a/drivers/net/ethernet/microsoft/mana/mana_en.c
+++ b/drivers/net/ethernet/microsoft/mana/mana_en.c

[...]

quoted

@@ -1659,6 +1679,8 @@ static void mana_poll_rx_cq(struct mana_cq *cq)

  	if (rxq->xdp_flush)
  		xdp_do_flush();
+
+	page_pool_nid_changed(rxq->page_pool, numa_mem_id());

I don't think this page_pool_nid_changed() called is needed, if you do
as I suggest below (nid = NUMA_NO_NODE).

quoted

  }

  static int mana_cq_handler(void *context, struct gdma_queue

*gdma_queue)
[...]

quoted

@@ -2008,6 +2041,25 @@ static int mana_push_wqe(struct mana_rxq *rxq)
  	return 0;
  }

+static int mana_create_page_pool(struct mana_rxq *rxq)
+{
+	struct page_pool_params pprm = {};

You are implicitly assigning NUMA node id zero.

quoted

+	int ret;
+
+	pprm.pool_size = RX_BUFFERS_PER_QUEUE;
+	pprm.napi = &rxq->rx_cq.napi;

You likely want to assign pprm.nid to NUMA_NO_NODE

  pprm.nid = NUMA_NO_NODE;

For most drivers it is recommended to assign ``NUMA_NO_NODE`` (value -1)
as the NUMA ID to ``pp_params.nid``. When ``CONFIG_NUMA`` is enabled
this setting will automatically select the (preferred) NUMA node (via
``numa_mem_id()``) based on where NAPI RX-processing is currently
running. The effect is that page_pool will only use recycled memory when
NUMA node match running CPU. This assumes CPU refilling driver RX-ring
will also run RX-NAPI.

If a driver want more control over the NUMA node memory selection,
drivers can assign (``pp_params.nid``) something else than
`NUMA_NO_NODE`` and runtime adjust via function
``page_pool_nid_changed()``.

Our driver is using NUMA 0 by default, so I implicitly assign NUMA node id 
to zero during pool init. 

And, if the IRQ/CPU affinity is changed, the page_pool_nid_changed()
will update the nid for the pool. Does this sound good?

Thanks,
-Haiyang