[PATCH] net: dpaa:reduce number of synchronize_net() calls

[PATCH] net: dpaa:reduce number of synchronize_net() calls

[Xi Huang]

In the function dpaa_napi_del(), we execute the netif_napi_del()
for each cpu, which is actually a high overhead operation
because each call to netif_napi_del() contains a synchronize_net(),
i.e. an RCU operation. In fact, it is only necessary to call
 __netif_napi_del and use synchronize_net() once outside of the loop.
like commit 2543a6000e,5198d545db. here is the function definition:
 static inline void netif_napi_del(struct napi_struct * napi)
{
	__netif_napi_del(napi).
	synchronize_net();
}

Signed-off-by: Xi Huang <xuiagnh@gmail.com>
---
 drivers/net/ethernet/freescale/dpaa/dpaa_eth.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/freescale/dpaa/dpaa_eth.c b/drivers/net/ethernet/freescale/dpaa/dpaa_eth.c
index cfe6b57b1..5d99cfb4e 100644
--- a/drivers/net/ethernet/freescale/dpaa/dpaa_eth.c
+++ b/drivers/net/ethernet/freescale/dpaa/dpaa_eth.c
@@ -3156,8 +3156,9 @@ static void dpaa_napi_del(struct net_device *net_dev)
 	for_each_possible_cpu(cpu) {
 		percpu_priv = per_cpu_ptr(priv->percpu_priv, cpu);
 
-		netif_napi_del(&percpu_priv->np.napi);
+		__netif_napi_del(&percpu_priv->np.napi);
 	}
+	synchronize_net();
 }
 
 static inline void dpaa_bp_free_pf(const struct dpaa_bp *bp,
-- 
2.34.1

Re: [PATCH] net: dpaa:reduce number of synchronize_net() calls

[Eric Dumazet]

On Thu, Aug 22, 2024 at 5:32 AM Xi Huang <xuiagnh@gmail.com> wrote:
>
> In the function dpaa_napi_del(), we execute the netif_napi_del()
> for each cpu, which is actually a high overhead operation
> because each call to netif_napi_del() contains a synchronize_net(),
> i.e. an RCU operation. In fact, it is only necessary to call
>  __netif_napi_del and use synchronize_net() once outside of the loop.
> like commit 2543a6000e,5198d545db.

Correct way of citing commits is to use 12+ chars of sha1 ("patch title") as in
commit 2543a6000e59 ("gro_cells: reduce number of synchronize_net() calls")

Quoting Documentation/dev-tools/checkpatch.rst :

  **GIT_COMMIT_ID**
    The proper way to reference a commit id is:
    commit <12+ chars of sha1> ("<title line>")

    An example may be::

      Commit e21d2170f36602ae2708 ("video: remove unnecessary
      platform_set_drvdata()") removed the unnecessary
      platform_set_drvdata(), but left the variable "dev" unused,
      delete it.

    See: https://www.kernel.org/doc/html/latest/process/submitting-patches.html#describe-your-changes


> here is the function definition:
>  static inline void netif_napi_del(struct napi_struct * napi)
> {
>         __netif_napi_del(napi).
>         synchronize_net();
> }

You do not need to include netif_napi_del() in this changelog.

Please send a V2 in ~24 hours and add this :

Reviewed-by: Eric Dumazet <edumazet@google.com>

Thank you.