[PATCH net-next-2.6] tg3: 64bits stats

[PATCH net-next-2.6] tg3: 64bits stats

[Eric Dumazet]

After commit be1f3c2c027c (net: Enable 64-bit net device statistics on
32-bit architectures), we can now provide 64bit stats, even on 32bit
arches.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
---
 drivers/net/tg3.c |   32 ++++++++++----------------------
 drivers/net/tg3.h |    4 ++--
 2 files changed, 12 insertions(+), 24 deletions(-)

diff --git a/drivers/net/tg3.c b/drivers/net/tg3.c
index 289cdc5..d1430f9 100644
--- a/drivers/net/tg3.c
+++ b/drivers/net/tg3.c
@@ -9021,7 +9021,7 @@ err_out1:
 	return err;
 }
 
-static struct net_device_stats *tg3_get_stats(struct net_device *);
+static struct rtnl_link_stats64 *tg3_get_stats64(struct net_device *);
 static struct tg3_ethtool_stats *tg3_get_estats(struct tg3 *);
 
 static int tg3_close(struct net_device *dev)
@@ -9055,7 +9055,7 @@ static int tg3_close(struct net_device *dev)
 
 	tg3_ints_fini(tp);
 
-	memcpy(&tp->net_stats_prev, tg3_get_stats(tp->dev),
+	memcpy(&tp->net_stats_prev, tg3_get_stats64(tp->dev),
 	       sizeof(tp->net_stats_prev));
 	memcpy(&tp->estats_prev, tg3_get_estats(tp),
 	       sizeof(tp->estats_prev));
@@ -9069,24 +9069,12 @@ static int tg3_close(struct net_device *dev)
 	return 0;
 }
 
-static inline unsigned long get_stat64(tg3_stat64_t *val)
-{
-	unsigned long ret;
-
-#if (BITS_PER_LONG == 32)
-	ret = val->low;
-#else
-	ret = ((u64)val->high << 32) | ((u64)val->low);
-#endif
-	return ret;
-}
-
-static inline u64 get_estat64(tg3_stat64_t *val)
+static inline u64 get_stat64(tg3_stat64_t *val)
 {
        return ((u64)val->high << 32) | ((u64)val->low);
 }
 
-static unsigned long calc_crc_errors(struct tg3 *tp)
+static u64 calc_crc_errors(struct tg3 *tp)
 {
 	struct tg3_hw_stats *hw_stats = tp->hw_stats;
 
@@ -9114,7 +9102,7 @@ static unsigned long calc_crc_errors(struct tg3 *tp)
 
 #define ESTAT_ADD(member) \
 	estats->member =	old_estats->member + \
-				get_estat64(&hw_stats->member)
+				get_stat64(&hw_stats->member)
 
 static struct tg3_ethtool_stats *tg3_get_estats(struct tg3 *tp)
 {
@@ -9204,11 +9192,11 @@ static struct tg3_ethtool_stats *tg3_get_estats(struct tg3 *tp)
 	return estats;
 }
 
-static struct net_device_stats *tg3_get_stats(struct net_device *dev)
+static struct rtnl_link_stats64 *tg3_get_stats64(struct net_device *dev)
 {
 	struct tg3 *tp = netdev_priv(dev);
-	struct net_device_stats *stats = &tp->net_stats;
-	struct net_device_stats *old_stats = &tp->net_stats_prev;
+	struct rtnl_link_stats64 *stats = &tp->net_stats;
+	struct rtnl_link_stats64 *old_stats = &tp->net_stats_prev;
 	struct tg3_hw_stats *hw_stats = tp->hw_stats;
 
 	if (!hw_stats)
@@ -14317,7 +14305,7 @@ static const struct net_device_ops tg3_netdev_ops = {
 	.ndo_open		= tg3_open,
 	.ndo_stop		= tg3_close,
 	.ndo_start_xmit		= tg3_start_xmit,
-	.ndo_get_stats		= tg3_get_stats,
+	.ndo_get_stats64	= tg3_get_stats64,
 	.ndo_validate_addr	= eth_validate_addr,
 	.ndo_set_multicast_list	= tg3_set_rx_mode,
 	.ndo_set_mac_address	= tg3_set_mac_addr,
@@ -14336,7 +14324,7 @@ static const struct net_device_ops tg3_netdev_ops_dma_bug = {
 	.ndo_open		= tg3_open,
 	.ndo_stop		= tg3_close,
 	.ndo_start_xmit		= tg3_start_xmit_dma_bug,
-	.ndo_get_stats		= tg3_get_stats,
+	.ndo_get_stats64	= tg3_get_stats64,
 	.ndo_validate_addr	= eth_validate_addr,
 	.ndo_set_multicast_list	= tg3_set_rx_mode,
 	.ndo_set_mac_address	= tg3_set_mac_addr,
diff --git a/drivers/net/tg3.h b/drivers/net/tg3.h
index 6b6af76..b72ac52 100644
--- a/drivers/net/tg3.h
+++ b/drivers/net/tg3.h
@@ -2772,8 +2772,8 @@ struct tg3 {
 
 
 	/* begin "everything else" cacheline(s) section */
-	struct net_device_stats		net_stats;
-	struct net_device_stats		net_stats_prev;
+	struct rtnl_link_stats64	net_stats;
+	struct rtnl_link_stats64	net_stats_prev;
 	struct tg3_ethtool_stats	estats;
 	struct tg3_ethtool_stats	estats_prev;
 

Re: [PATCH net-next-2.6] tg3: 64bits stats

[Eric Dumazet]

Le lundi 05 juillet 2010 à 11:14 +0200, Eric Dumazet a écrit :
> After commit be1f3c2c027c (net: Enable 64-bit net device statistics on
> 32-bit architectures), we can now provide 64bit stats, even on 32bit
> arches.
> 
> Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
> ---

Please disregard this patch.

There is small possibility a reader might read a 64bit value while
another writer makes a change to it, changing high 32bit value.

A change in core network would be needed to make this 100% safe,
possibly using a seqlock to protect dev->stats64

Re: [PATCH net-next-2.6] tg3: 64bits stats

[Ben Hutchings]

On Mon, 2010-07-05 at 18:03 +0200, Eric Dumazet wrote:
> Le lundi 05 juillet 2010 à 11:14 +0200, Eric Dumazet a écrit :
> > After commit be1f3c2c027c (net: Enable 64-bit net device statistics on
> > 32-bit architectures), we can now provide 64bit stats, even on 32bit
> > arches.
> > 
> > Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
> > ---
> 
> Please disregard this patch.
> 
> There is small possibility a reader might read a 64bit value while
> another writer makes a change to it, changing high 32bit value.
> 
> A change in core network would be needed to make this 100% safe,
> possibly using a seqlock to protect dev->stats64

I really didn't want to add this overhead and complication to readers
when only some drivers need it.

Ben.

-- 
Ben Hutchings, Senior Software Engineer, Solarflare Communications
Not speaking for my employer; that's the marketing department's job.
They asked us to note that Solarflare product names are trademarked.

Re: [PATCH net-next-2.6] tg3: 64bits stats

[Eric Dumazet]

Le lundi 05 juillet 2010 à 18:31 +0100, Ben Hutchings a écrit :
> On Mon, 2010-07-05 at 18:03 +0200, Eric Dumazet wrote:
> > Le lundi 05 juillet 2010 à 11:14 +0200, Eric Dumazet a écrit :
> > > After commit be1f3c2c027c (net: Enable 64-bit net device statistics on
> > > 32-bit architectures), we can now provide 64bit stats, even on 32bit
> > > arches.
> > > 
> > > Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
> > > ---
> > 
> > Please disregard this patch.
> > 
> > There is small possibility a reader might read a 64bit value while
> > another writer makes a change to it, changing high 32bit value.
> > 
> > A change in core network would be needed to make this 100% safe,
> > possibly using a seqlock to protect dev->stats64
> 
> I really didn't want to add this overhead and complication to readers
> when only some drivers need it.
> 

Overhead would be minimal, only in get_stats() method and only for
drivers that want to provide 64 bit stats...

Clearly, rx/tx path must not have any overhead.

Right now, even RTNL 64bit stats are not safe.

Should we revert prior patches or try to make progress ?

Re: [PATCH net-next-2.6] tg3: 64bits stats

[Ben Hutchings]

On Mon, 2010-07-05 at 20:07 +0200, Eric Dumazet wrote:
> Le lundi 05 juillet 2010 à 18:31 +0100, Ben Hutchings a écrit :
> > On Mon, 2010-07-05 at 18:03 +0200, Eric Dumazet wrote:
> > > Le lundi 05 juillet 2010 à 11:14 +0200, Eric Dumazet a écrit :
> > > > After commit be1f3c2c027c (net: Enable 64-bit net device statistics on
> > > > 32-bit architectures), we can now provide 64bit stats, even on 32bit
> > > > arches.
> > > > 
> > > > Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
> > > > ---
> > > 
> > > Please disregard this patch.
> > > 
> > > There is small possibility a reader might read a 64bit value while
> > > another writer makes a change to it, changing high 32bit value.
> > > 
> > > A change in core network would be needed to make this 100% safe,
> > > possibly using a seqlock to protect dev->stats64
> > 
> > I really didn't want to add this overhead and complication to readers
> > when only some drivers need it.
> > 
> 
> Overhead would be minimal, only in get_stats() method and only for
> drivers that want to provide 64 bit stats...
> 
> Clearly, rx/tx path must not have any overhead.
> 
> Right now, even RTNL 64bit stats are not safe.
> 
> Should we revert prior patches or try to make progress ?

I think you should use a similar approach here as you did in the
loopback driver, i.e. update private variables in the RX and TX path and
then copy/aggregate them in the implementation ndo_get_stats64 (only
without the need for percpu stats).

If you want to include a seqlock in the driver stats interface, you can
do that but it's not going to be pretty and we're still going to need
additional seqlocks for per-queue (or percpy) stats in some drivers.

Ben.

-- 
Ben Hutchings, Senior Software Engineer, Solarflare Communications
Not speaking for my employer; that's the marketing department's job.
They asked us to note that Solarflare product names are trademarked.

Re: [PATCH net-next-2.6] tg3: 64bits stats

[Eric Dumazet]

Le lundi 05 juillet 2010 à 19:30 +0100, Ben Hutchings a écrit :

> I think you should use a similar approach here as you did in the
> loopback driver, i.e. update private variables in the RX and TX path and
> then copy/aggregate them in the implementation ndo_get_stats64 (only
> without the need for percpu stats).
> 
> If you want to include a seqlock in the driver stats interface, you can
> do that but it's not going to be pretty and we're still going to need
> additional seqlocks for per-queue (or percpy) stats in some drivers.

Yes, I provided one patch but am working on a different one, requiring a
new rtnl_link_stats64 param to ndo_get_stats64() methods and
dev_get_stats() as well.

dev->stats64 should not be overwritten without some synchronization, so
just disallow it for the moment...

Re: [PATCH net-next-2.6] tg3: 64bits stats

[Ben Hutchings]

On Mon, 2010-07-05 at 20:07 +0200, Eric Dumazet wrote:
> Le lundi 05 juillet 2010 à 18:31 +0100, Ben Hutchings a écrit :
> > On Mon, 2010-07-05 at 18:03 +0200, Eric Dumazet wrote:
> > > Le lundi 05 juillet 2010 à 11:14 +0200, Eric Dumazet a écrit :
> > > > After commit be1f3c2c027c (net: Enable 64-bit net device statistics on
> > > > 32-bit architectures), we can now provide 64bit stats, even on 32bit
> > > > arches.
> > > > 
> > > > Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
> > > > ---
> > > 
> > > Please disregard this patch.
> > > 
> > > There is small possibility a reader might read a 64bit value while
> > > another writer makes a change to it, changing high 32bit value.
> > > 
> > > A change in core network would be needed to make this 100% safe,
> > > possibly using a seqlock to protect dev->stats64
> > 
> > I really didn't want to add this overhead and complication to readers
> > when only some drivers need it.
> > 
> 
> Overhead would be minimal, only in get_stats() method and only for
> drivers that want to provide 64 bit stats...
> 
> Clearly, rx/tx path must not have any overhead.
> 
> Right now, even RTNL 64bit stats are not safe.

Ugh, I was assuming that callers of dev_get_stats() would hold
dev_base_lock.  However only netstat_show() seems to do so currently.

Ben.

> Should we revert prior patches or try to make progress ?
> 
> 
> 
-- 
Ben Hutchings, Senior Software Engineer, Solarflare Communications
Not speaking for my employer; that's the marketing department's job.
They asked us to note that Solarflare product names are trademarked.

Re: [PATCH net-next-2.6] tg3: 64bits stats

[Eric Dumazet]

Le lundi 05 juillet 2010 à 19:41 +0100, Ben Hutchings a écrit :
> Ugh, I was assuming that callers of dev_get_stats() would hold
> dev_base_lock.  However only netstat_show() seems to do so currently.

Right, but a read_lock() would not be enough, even if all users would
use it.