This is a note to let you know that I've just added the patch titled
net: stmmac: Fix overall budget calculation for rxtx_napi
to the 5.14-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
net-stmmac-fix-overall-budget-calculation-for-rxtx_napi.patch
and it can be found in the queue-5.14 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 81d0885d68ec427e62044cf46a400c9958ea0092 Mon Sep 17 00:00:00 2001
From: Song Yoong Siang <yoong.siang.song@xxxxxxxxx>
Date: Fri, 3 Sep 2021 10:00:26 +0800
Subject: net: stmmac: Fix overall budget calculation for rxtx_napi
From: Song Yoong Siang <yoong.siang.song@xxxxxxxxx>
commit 81d0885d68ec427e62044cf46a400c9958ea0092 upstream.
tx_done is not used for napi_complete_done(). Thus, NAPI busy polling
mechanism by gro_flush_timeout and napi_defer_hard_irqs will not able
be triggered after a packet is transmitted when there is no receive
packet.
Fix this by taking the maximum value between tx_done and rx_done as
overall budget completed by the rxtx NAPI poll to ensure XDP Tx ZC
operation is continuously polling for next Tx frame. This gives
benefit of lower packet submission processing latency and jitter
under XDP Tx ZC mode.
Performance of tx-only using xdp-sock on Intel ADL-S platform is
the same with and without this patch.
root@intel-corei7-64:~# ./xdpsock -i enp0s30f4 -t -z -q 1 -n 10
sock0@enp0s30f4:1 txonly xdp-drv
pps pkts 10.00
rx 0 0
tx 511630 8659520
sock0@enp0s30f4:1 txonly xdp-drv
pps pkts 10.00
rx 0 0
tx 511625 13775808
sock0@enp0s30f4:1 txonly xdp-drv
pps pkts 10.00
rx 0 0
tx 511619 18892032
Fixes: 132c32ee5bc0 ("net: stmmac: Add TX via XDP zero-copy socket")
Cc: <stable@xxxxxxxxxxxxxxx> # 5.13.x
Co-developed-by: Ong Boon Leong <boon.leong.ong@xxxxxxxxx>
Signed-off-by: Ong Boon Leong <boon.leong.ong@xxxxxxxxx>
Signed-off-by: Song Yoong Siang <yoong.siang.song@xxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
@@ -5342,7 +5342,7 @@ static int stmmac_napi_poll_rxtx(struct
struct stmmac_channel *ch =
container_of(napi, struct stmmac_channel, rxtx_napi);
struct stmmac_priv *priv = ch->priv_data;
- int rx_done, tx_done;
+ int rx_done, tx_done, rxtx_done;
u32 chan = ch->index;
priv->xstats.napi_poll++;
@@ -5352,14 +5352,16 @@ static int stmmac_napi_poll_rxtx(struct
rx_done = stmmac_rx_zc(priv, budget, chan);
+ rxtx_done = max(tx_done, rx_done);
+
/* If either TX or RX work is not complete, return budget
* and keep pooling
*/
- if (tx_done >= budget || rx_done >= budget)
+ if (rxtx_done >= budget)
return budget;
/* all work done, exit the polling mode */
- if (napi_complete_done(napi, rx_done)) {
+ if (napi_complete_done(napi, rxtx_done)) {
unsigned long flags;
spin_lock_irqsave(&ch->lock, flags);
@@ -5370,7 +5372,7 @@ static int stmmac_napi_poll_rxtx(struct
spin_unlock_irqrestore(&ch->lock, flags);
}
- return min(rx_done, budget - 1);
+ return min(rxtx_done, budget - 1);
}
/**
Patches currently in stable-queue which might be from yoong.siang.song@xxxxxxxxx are
queue-5.14/net-stmmac-fix-overall-budget-calculation-for-rxtx_napi.patch
