[PATCH V2,net] net: mana: Fix perf regression: remove rx_cqes, tx_cqes counters

[PATCH V2,net] net: mana: Fix perf regression: remove rx_cqes, tx_cqes counters

[Haiyang Zhang]

The apc->eth_stats.rx_cqes is one per NIC (vport), and it's on the
frequent and parallel code path of all queues. So, r/w into this
single shared variable by many threads on different CPUs creates a
lot caching and memory overhead, hence perf regression. And, it's
not accurate due to the high volume concurrent r/w.

Since the error path of mana_poll_rx_cq() already has warnings, so
keeping the counter and convert it to a per-queue variable is not
necessary. So, just remove this counter from this high frequency
code path.

Also, remove the tx_cqes counter for the same reason. We have
warnings & other counters for errors on that path, and don't need
to count every normal cqe processing.

Cc: stable@vger.kernel.org
Fixes: bd7fc6e1957c ("net: mana: Add new MANA VF performance counters for easier troubleshooting")
Signed-off-by: Haiyang Zhang <haiyangz@microsoft.com>
---
V2:
	Same as V1, except adding more Cc's.
---
 drivers/net/ethernet/microsoft/mana/mana_en.c      | 10 ----------
 drivers/net/ethernet/microsoft/mana/mana_ethtool.c |  2 --
 include/net/mana/mana.h                            |  2 --
 3 files changed, 14 deletions(-)

diff --git a/drivers/net/ethernet/microsoft/mana/mana_en.c b/drivers/net/ethernet/microsoft/mana/mana_en.c
index 06d6292e09b3..d907727c7b7a 100644
--- a/drivers/net/ethernet/microsoft/mana/mana_en.c
+++ b/drivers/net/ethernet/microsoft/mana/mana_en.c
@@ -1279,8 +1279,6 @@ static void mana_poll_tx_cq(struct mana_cq *cq)
 	if (comp_read < 1)
 		return;
 
-	apc->eth_stats.tx_cqes = comp_read;
-
 	for (i = 0; i < comp_read; i++) {
 		struct mana_tx_comp_oob *cqe_oob;
 
@@ -1363,8 +1361,6 @@ static void mana_poll_tx_cq(struct mana_cq *cq)
 		WARN_ON_ONCE(1);
 
 	cq->work_done = pkt_transmitted;
-
-	apc->eth_stats.tx_cqes -= pkt_transmitted;
 }
 
 static void mana_post_pkt_rxq(struct mana_rxq *rxq)
@@ -1626,15 +1622,11 @@ static void mana_poll_rx_cq(struct mana_cq *cq)
 {
 	struct gdma_comp *comp = cq->gdma_comp_buf;
 	struct mana_rxq *rxq = cq->rxq;
-	struct mana_port_context *apc;
 	int comp_read, i;
 
-	apc = netdev_priv(rxq->ndev);
-
 	comp_read = mana_gd_poll_cq(cq->gdma_cq, comp, CQE_POLLING_BUFFER);
 	WARN_ON_ONCE(comp_read > CQE_POLLING_BUFFER);
 
-	apc->eth_stats.rx_cqes = comp_read;
 	rxq->xdp_flush = false;
 
 	for (i = 0; i < comp_read; i++) {
@@ -1646,8 +1638,6 @@ static void mana_poll_rx_cq(struct mana_cq *cq)
 			return;
 
 		mana_process_rx_cqe(rxq, cq, &comp[i]);
-
-		apc->eth_stats.rx_cqes--;
 	}
 
 	if (rxq->xdp_flush)
diff --git a/drivers/net/ethernet/microsoft/mana/mana_ethtool.c b/drivers/net/ethernet/microsoft/mana/mana_ethtool.c
index a64c81410dc1..0dc78679f620 100644
--- a/drivers/net/ethernet/microsoft/mana/mana_ethtool.c
+++ b/drivers/net/ethernet/microsoft/mana/mana_ethtool.c
@@ -13,11 +13,9 @@ static const struct {
 } mana_eth_stats[] = {
 	{"stop_queue", offsetof(struct mana_ethtool_stats, stop_queue)},
 	{"wake_queue", offsetof(struct mana_ethtool_stats, wake_queue)},
-	{"tx_cqes", offsetof(struct mana_ethtool_stats, tx_cqes)},
 	{"tx_cq_err", offsetof(struct mana_ethtool_stats, tx_cqe_err)},
 	{"tx_cqe_unknown_type", offsetof(struct mana_ethtool_stats,
 					tx_cqe_unknown_type)},
-	{"rx_cqes", offsetof(struct mana_ethtool_stats, rx_cqes)},
 	{"rx_coalesced_err", offsetof(struct mana_ethtool_stats,
 					rx_coalesced_err)},
 	{"rx_cqe_unknown_type", offsetof(struct mana_ethtool_stats,
diff --git a/include/net/mana/mana.h b/include/net/mana/mana.h
index cd386aa7c7cc..9eef19972845 100644
--- a/include/net/mana/mana.h
+++ b/include/net/mana/mana.h
@@ -347,10 +347,8 @@ struct mana_tx_qp {
 struct mana_ethtool_stats {
 	u64 stop_queue;
 	u64 wake_queue;
-	u64 tx_cqes;
 	u64 tx_cqe_err;
 	u64 tx_cqe_unknown_type;
-	u64 rx_cqes;
 	u64 rx_coalesced_err;
 	u64 rx_cqe_unknown_type;
 };
-- 
2.25.1

Re: [PATCH V2,net] net: mana: Fix perf regression: remove rx_cqes, tx_cqes counters

[Jakub Kicinski]

On Thu, 25 May 2023 07:46:30 -0700 Haiyang Zhang wrote:
> lot caching and memory overhead, hence perf regression.

Horatiu's ask for more details was perfectly reasonable.
Provide more details to give the distros and users an
idea of the order of magnitude of the problem. Example
workload and relative perf hit, anything.

Please do not repost within 24 hours:
https://www.kernel.org/doc/html/next/process/maintainer-netdev.html
-- 
pw-bot: cr

RE: [PATCH V2,net] net: mana: Fix perf regression: remove rx_cqes, tx_cqes counters

[Haiyang Zhang]

> -----Original Message-----
> From: Jakub Kicinski <kuba@kernel.org>
> Sent: Thursday, May 25, 2023 11:26 PM
> To: Haiyang Zhang <haiyangz@microsoft.com>
> Cc: linux-hyperv@vger.kernel.org; netdev@vger.kernel.org; Dexuan Cui
> <decui@microsoft.com>; KY Srinivasan <kys@microsoft.com>; Paul Rosswurm
> <paulros@microsoft.com>; olaf@aepfle.de; vkuznets@redhat.com;
> davem@davemloft.net; wei.liu@kernel.org; edumazet@google.com;
> pabeni@redhat.com; leon@kernel.org; Long Li <longli@microsoft.com>;
> 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 <sharmaajay@microsoft.com>;
> hawk@kernel.org; tglx@linutronix.de; shradhagupta@linux.microsoft.com;
> linux-kernel@vger.kernel.org; stable@vger.kernel.org
> Subject: Re: [PATCH V2,net] net: mana: Fix perf regression: remove rx_cqes,
> tx_cqes counters
> 
> On Thu, 25 May 2023 07:46:30 -0700 Haiyang Zhang wrote:
> > lot caching and memory overhead, hence perf regression.
> 
> Horatiu's ask for more details was perfectly reasonable.
> Provide more details to give the distros and users an
> idea of the order of magnitude of the problem. Example
> workload and relative perf hit, anything.

For example, a workload is iperf with 128 threads, and with RPS enabled.
We saw perf regression of 25% with the previous patch adding the counters.
And this patch eliminates the regression. 

Thanks,
- Haiyang

Re: [PATCH V2,net] net: mana: Fix perf regression: remove rx_cqes, tx_cqes counters

[Jakub Kicinski]

On Fri, 26 May 2023 14:42:07 +0000 Haiyang Zhang wrote:
> > Horatiu's ask for more details was perfectly reasonable.
> > Provide more details to give the distros and users an
> > idea of the order of magnitude of the problem. Example
> > workload and relative perf hit, anything.  
> 
> For example, a workload is iperf with 128 threads, and with RPS enabled.
> We saw perf regression of 25% with the previous patch adding the counters.
> And this patch eliminates the regression. 

Exactly what I was looking for, thanks. Please put that in the commit
message and post v3 (feel free to add the review tags which came in for
v1 in the meantime).

RE: [PATCH V2,net] net: mana: Fix perf regression: remove rx_cqes, tx_cqes counters

[Haiyang Zhang]

> -----Original Message-----
> From: Jakub Kicinski <kuba@kernel.org>
> Sent: Friday, May 26, 2023 11:28 AM
> To: Haiyang Zhang <haiyangz@microsoft.com>
> Cc: linux-hyperv@vger.kernel.org; netdev@vger.kernel.org; Dexuan Cui
> <decui@microsoft.com>; KY Srinivasan <kys@microsoft.com>; Paul Rosswurm
> <paulros@microsoft.com>; olaf@aepfle.de; vkuznets@redhat.com;
> davem@davemloft.net; wei.liu@kernel.org; edumazet@google.com;
> pabeni@redhat.com; leon@kernel.org; Long Li <longli@microsoft.com>;
> 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 <sharmaajay@microsoft.com>;
> hawk@kernel.org; tglx@linutronix.de; shradhagupta@linux.microsoft.com;
> linux-kernel@vger.kernel.org; stable@vger.kernel.org
> Subject: Re: [PATCH V2,net] net: mana: Fix perf regression: remove rx_cqes,
> tx_cqes counters
> 
> On Fri, 26 May 2023 14:42:07 +0000 Haiyang Zhang wrote:
> > > Horatiu's ask for more details was perfectly reasonable.
> > > Provide more details to give the distros and users an
> > > idea of the order of magnitude of the problem. Example
> > > workload and relative perf hit, anything.
> >
> > For example, a workload is iperf with 128 threads, and with RPS enabled.
> > We saw perf regression of 25% with the previous patch adding the counters.
> > And this patch eliminates the regression.
> 
> Exactly what I was looking for, thanks. Please put that in the commit
> message and post v3 (feel free to add the review tags which came in for
> v1 in the meantime).

Will do.

Thanks!