Hi Dan,
On 3/3/2025 7:38 PM, Dan Carpenter wrote:
What I mean is just compile the .o file with and without the unlikely().
$ md5sum drivers/net/ethernet/ti/icssg/icssg_common. o*
2de875935222b9ecd8483e61848c4fc9 drivers/net/ethernet/ti/icssg/
icssg_common. o. annotation 2de875935222b9ecd8483e61848c4fc9
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What I mean is just compile the .o file with and without the unlikely().
$ md5sum drivers/net/ethernet/ti/icssg/icssg_common.o*
2de875935222b9ecd8483e61848c4fc9 drivers/net/ethernet/ti/icssg/icssg_common.o.annotation
2de875935222b9ecd8483e61848c4fc9 drivers/net/ethernet/ti/icssg/icssg_common.o.no_anotation
Generally the rule is that you should leave likely/unlikely() annotations
out unless it's going to make a difference on a benchmark. I'm not going
to jump down people's throat about this, and if you want to leave it,
it's fine. But it just struct me as weird so that's why I commented on
it.
I have done some performance tests to see if unlikely() is gonna make
any impact and I see around ~9000 pps and 6Mbps drop without unlikely()
for small packet sizes (60 Bytes)
You can see summary of the tests here:
packet size with unlikely(pps) without unlikely(pps) regression
60 462377 453251 9126
80 403020 399372 3648
96 402059 396881 5178
120 392725 391312 4413
140 327706 327099 607
packet size with unlikely(Mbps) without unlikely(Mbps) regression
60 311 305 6
80 335 332 3
96 386 381 5
120 456 451 5
140 430 429 1
For more details on the logs, please
refer:https://gist.github.com/MeghanaMalladiTI/cc6cc7709791376cb486eb1222de67be
Regards,
Meghana Malladi
regards,
dan carpenter
diff --git a/drivers/net/ethernet/ti/icssg/icssg_common.c b/drivers/net/ethernet/ti/icssg/icssg_common.c
index 34d16e00c2ec..3db5bae44e61 100644
--- a/drivers/net/ethernet/ti/icssg/icssg_common.c
+++ b/drivers/net/ethernet/ti/icssg/icssg_common.c
@@ -672,7 +672,7 @@ static int emac_run_xdp(struct prueth_emac *emac, struct xdp_buff *xdp,
case XDP_TX:
/* Send packet to TX ring for immediate transmission */
xdpf = xdp_convert_buff_to_frame(xdp);
- if (unlikely(!xdpf))
+ if (!xdpf)
goto drop;
q_idx = smp_processor_id() % emac->tx_ch_num;
