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Date: Thu, 21 Aug 2014 15:04:24 -0700
From: Benjamin Poirier <bpoirier@...e.de>
To: Michael Chan <mchan@...adcom.com>
Cc: Prashant Sreedharan <prashant@...adcom.com>,
netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] tg3: Limit minimum tx queue wakeup threshold
On 2014/08/19 15:00, Michael Chan wrote:
> On Tue, 2014-08-19 at 11:52 -0700, Benjamin Poirier wrote:
> > diff --git a/drivers/net/ethernet/broadcom/tg3.c b/drivers/net/ethernet/broadcom/tg3.c
> > index 3ac5d23..b11c0fd 100644
> > --- a/drivers/net/ethernet/broadcom/tg3.c
> > +++ b/drivers/net/ethernet/broadcom/tg3.c
> > @@ -202,7 +202,8 @@ static inline void _tg3_flag_clear(enum TG3_FLAGS flag, unsigned long *bits)
> > #endif
> >
> > /* minimum number of free TX descriptors required to wake up TX process */
> > -#define TG3_TX_WAKEUP_THRESH(tnapi) ((tnapi)->tx_pending / 4)
> > +#define TG3_TX_WAKEUP_THRESH(tnapi) max_t(u32, (tnapi)->tx_pending / 4, \
> > + MAX_SKB_FRAGS + 1)
>
> I think we should precompute this and store it in something like
> tp->tx_wake_thresh.
I've tried this by adding the following patch at the end of the v2
series but I did not measure a significant latency improvement. Was
there another reason for the change?
Here are the performance results. The first set of numbers are the same
as those found in patch v2 3/3.
# perf stat -r10 -ad netperf -H 192.168.9.30 -l60 -T 0,0 -t omni -- -d rr
* with patches 1-3
rr values: 6732.65 6920.1 6909.46 7032.41 6864.43 6897.6 6815.19 6967.83 6849.23 6929.52
sample size: 10
mean: 6891.842
standard deviation: 82.91901
quantiles: 6732.65 6853.03 6903.53 6927.165 7032.41
6890±80
Performance counter stats for 'netperf -H 192.168.9.30 -l60 -T 0,0 -t omni -- -d rr' (10 runs):
480675.949728 task-clock # 8.001 CPUs utilized ( +- 0.01% ) [100.00%]
850,461 context-switches # 0.002 M/sec ( +- 0.37% ) [100.00%]
564 CPU-migrations # 0.000 M/sec ( +- 5.67% ) [100.00%]
417 page-faults # 0.000 M/sec ( +- 76.04% )
287,019,442,295 cycles # 0.597 GHz ( +- 7.16% ) [15.01%]
828,198,830,689 stalled-cycles-frontend # 288.55% frontend cycles idle ( +- 3.01% ) [25.01%]
718,230,307,166 stalled-cycles-backend # 250.24% backend cycles idle ( +- 3.53% ) [35.00%]
117,976,598,188 instructions # 0.41 insns per cycle
# 7.02 stalled cycles per insn ( +- 4.06% ) [45.00%]
26,715,853,108 branches # 55.580 M/sec ( +- 3.77% ) [50.00%]
198,787,673 branch-misses # 0.74% of all branches ( +- 0.86% ) [50.00%]
28,416,922,166 L1-dcache-loads # 59.119 M/sec ( +- 3.54% ) [50.00%]
367,613,007 L1-dcache-load-misses # 1.29% of all L1-dcache hits ( +- 0.47% ) [50.00%]
75,260,575 LLC-loads # 0.157 M/sec ( +- 2.24% ) [40.00%]
5,777 LLC-load-misses # 0.01% of all LL-cache hits ( +- 36.03% ) [ 5.00%]
60.077898757 seconds time elapsed ( +- 0.01% )
* with patches 1-3 + tx_wake_thresh_def
rr values: 6636.87 6874.05 6916.29 6961.68 6941.3 6841.44 6829.05 6806.55 6846.04 6958.39
sample size: 10
mean: 6861.166
standard deviation: 96.67967
quantiles: 6636.87 6832.148 6860.045 6935.048 6961.68
6900±100
Performance counter stats for 'netperf -H 192.168.9.30 -l60 -T 0,0 -t omni -- -d rr' (10 runs):
480688.653656 task-clock # 8.001 CPUs utilized ( +- 0.01% ) [100.00%]
846,980 context-switches # 0.002 M/sec ( +- 0.40% ) [100.00%]
524 CPU-migrations # 0.000 M/sec ( +- 11.82% ) [100.00%]
420 page-faults # 0.000 M/sec ( +- 75.31% )
275,602,421,981 cycles # 0.573 GHz ( +- 3.23% ) [15.01%]
806,335,406,844 stalled-cycles-frontend # 292.57% frontend cycles idle ( +- 2.16% ) [25.01%]
640,757,376,054 stalled-cycles-backend # 232.49% backend cycles idle ( +- 2.46% ) [35.00%]
113,241,018,220 instructions # 0.41 insns per cycle
# 7.12 stalled cycles per insn ( +- 1.93% ) [45.00%]
25,479,064,973 branches # 53.005 M/sec ( +- 1.96% ) [50.00%]
205,483,191 branch-misses # 0.81% of all branches ( +- 0.75% ) [50.00%]
27,209,883,125 L1-dcache-loads # 56.606 M/sec ( +- 1.87% ) [50.00%]
361,721,478 L1-dcache-load-misses # 1.33% of all L1-dcache hits ( +- 0.51% ) [50.00%]
80,669,260 LLC-loads # 0.168 M/sec ( +- 1.01% ) [40.00%]
8,846 LLC-load-misses # 0.01% of all LL-cache hits ( +- 34.01% ) [ 5.00%]
60.079761525 seconds time elapsed ( +- 0.01% )
---
drivers/net/ethernet/broadcom/tg3.c | 27 ++++++++++++++++-----------
drivers/net/ethernet/broadcom/tg3.h | 5 +++--
2 files changed, 19 insertions(+), 13 deletions(-)
diff --git a/drivers/net/ethernet/broadcom/tg3.c b/drivers/net/ethernet/broadcom/tg3.c
index c29f2e3..81e390b 100644
--- a/drivers/net/ethernet/broadcom/tg3.c
+++ b/drivers/net/ethernet/broadcom/tg3.c
@@ -6478,10 +6478,11 @@ static void tg3_dump_state(struct tg3 *tp)
tnapi->hw_status->idx[0].tx_consumer);
netdev_err(tp->dev,
- "%d: NAPI info [%08x:%08x:(%04x:%04x:%04x):%04x:(%04x:%04x:%04x:%04x)]\n",
+ "%d: NAPI info [%08x:%08x:(%04x:%04x:%04x:%04x):%04x:(%04x:%04x:%04x:%04x)]\n",
i,
tnapi->last_tag, tnapi->last_irq_tag,
tnapi->tx_prod, tnapi->tx_cons, tnapi->tx_pending,
+ tnapi->tx_wake_thresh_cur,
tnapi->rx_rcb_ptr,
tnapi->prodring.rx_std_prod_idx,
tnapi->prodring.rx_std_cons_idx,
@@ -6613,10 +6614,10 @@ static void tg3_tx(struct tg3_napi *tnapi)
smp_mb();
if (unlikely(netif_tx_queue_stopped(txq) &&
- (tg3_tx_avail(tnapi) > tnapi->wakeup_thresh))) {
+ (tg3_tx_avail(tnapi) > tnapi->tx_wake_thresh_cur))) {
__netif_tx_lock(txq, smp_processor_id());
if (netif_tx_queue_stopped(txq) &&
- (tg3_tx_avail(tnapi) > tnapi->wakeup_thresh))
+ (tg3_tx_avail(tnapi) > tnapi->tx_wake_thresh_cur))
netif_tx_wake_queue(txq);
__netif_tx_unlock(txq);
}
@@ -7849,8 +7850,8 @@ static int tg3_tso_bug(struct tg3 *tp, struct tg3_napi *tnapi,
if (unlikely(tg3_tx_avail(tnapi) <= desc_cnt_est)) {
netif_tx_stop_queue(txq);
- tnapi->wakeup_thresh = desc_cnt_est;
- BUG_ON(tnapi->wakeup_thresh >= tnapi->tx_pending);
+ tnapi->tx_wake_thresh_cur = desc_cnt_est;
+ BUG_ON(tnapi->tx_wake_thresh_cur >= tnapi->tx_pending);
/* netif_tx_stop_queue() must be done before checking
* checking tx index in tg3_tx_avail() below, because in
@@ -7858,7 +7859,7 @@ static int tg3_tso_bug(struct tg3 *tp, struct tg3_napi *tnapi,
* netif_tx_queue_stopped().
*/
smp_mb();
- if (tg3_tx_avail(tnapi) <= tnapi->wakeup_thresh)
+ if (tg3_tx_avail(tnapi) <= tnapi->tx_wake_thresh_cur)
return NETDEV_TX_BUSY;
netif_tx_wake_queue(txq);
@@ -7938,14 +7939,14 @@ static netdev_tx_t __tg3_start_xmit(struct sk_buff *skb,
if (unlikely(budget <= (skb_shinfo(skb)->nr_frags + 1))) {
if (!netif_tx_queue_stopped(txq)) {
netif_tx_stop_queue(txq);
- tnapi->wakeup_thresh = TG3_TX_WAKEUP_THRESH(tnapi);
+ tnapi->tx_wake_thresh_cur = tnapi->tx_wake_thresh_def;
/* This is a hard error, log it. */
netdev_err(dev,
"BUG! Tx Ring full when queue awake!\n");
}
smp_mb();
- if (tg3_tx_avail(tnapi) <= tnapi->wakeup_thresh)
+ if (tg3_tx_avail(tnapi) <= tnapi->tx_wake_thresh_cur)
return NETDEV_TX_BUSY;
netif_tx_wake_queue(txq);
@@ -8127,7 +8128,7 @@ static netdev_tx_t __tg3_start_xmit(struct sk_buff *skb,
tnapi->tx_prod = entry;
if (unlikely(tg3_tx_avail(tnapi) <= stop_thresh)) {
netif_tx_stop_queue(txq);
- tnapi->wakeup_thresh = TG3_TX_WAKEUP_THRESH(tnapi);
+ tnapi->tx_wake_thresh_cur = tnapi->tx_wake_thresh_def;
/* netif_tx_stop_queue() must be done before checking
* checking tx index in tg3_tx_avail() below, because in
@@ -8135,7 +8136,7 @@ static netdev_tx_t __tg3_start_xmit(struct sk_buff *skb,
* netif_tx_queue_stopped().
*/
smp_mb();
- if (tg3_tx_avail(tnapi) > tnapi->wakeup_thresh)
+ if (tg3_tx_avail(tnapi) > tnapi->tx_wake_thresh_cur)
netif_tx_wake_queue(txq);
}
@@ -12379,8 +12380,11 @@ static int tg3_set_ringparam(struct net_device *dev, struct ethtool_ringparam *e
tp->rx_jumbo_pending = ering->rx_jumbo_pending;
dev->gso_max_segs = TG3_TX_SEG_PER_DESC(ering->tx_pending - 1);
- for (i = 0; i < tp->irq_max; i++)
+ for (i = 0; i < tp->irq_max; i++) {
tp->napi[i].tx_pending = ering->tx_pending;
+ tp->napi[i].tx_wake_thresh_def =
+ TG3_TX_WAKEUP_THRESH(&tp->napi[i]);
+ }
if (netif_running(dev)) {
tg3_halt(tp, RESET_KIND_SHUTDOWN, 1);
@@ -17820,6 +17824,7 @@ static int tg3_init_one(struct pci_dev *pdev,
tnapi->tp = tp;
tnapi->tx_pending = TG3_DEF_TX_RING_PENDING;
+ tnapi->tx_wake_thresh_def = TG3_TX_WAKEUP_THRESH(tnapi);
tnapi->int_mbox = intmbx;
if (i <= 4)
diff --git a/drivers/net/ethernet/broadcom/tg3.h b/drivers/net/ethernet/broadcom/tg3.h
index 6a7e13d..44a21cb 100644
--- a/drivers/net/ethernet/broadcom/tg3.h
+++ b/drivers/net/ethernet/broadcom/tg3.h
@@ -3004,11 +3004,12 @@ struct tg3_napi {
u32 tx_prod ____cacheline_aligned;
u32 tx_cons;
u32 tx_pending;
- u32 last_tx_cons;
u32 prodmbox;
- u32 wakeup_thresh;
+ u32 tx_wake_thresh_cur;
+ u32 tx_wake_thresh_def;
struct tg3_tx_buffer_desc *tx_ring;
struct tg3_tx_ring_info *tx_buffers;
+ u32 last_tx_cons;
dma_addr_t status_mapping;
dma_addr_t rx_rcb_mapping;
--
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