On Thu, 2020-07-02 at 21:25 -0700, Jakub Kicinski wrote:
> On Fri, 3 Jul 2020 03:45:45 +0000 Saeed Mahameed wrote:
> > On Thu, 2020-07-02 at 18:47 -0700, Jakub Kicinski wrote:
> > > On Thu, 2 Jul 2020 15:19:14 -0700 Saeed Mahameed wrote:
> > > > From: Ron Diskin <ro...@mellanox.com>
> > > >
> > > > Currently the FW does not generate events for counters other
> > > > than
> > > > error
> > > > counters. Unlike ".get_ethtool_stats", ".ndo_get_stats64"
> > > > (which ip
> > > > -s
> > > > uses) might run in atomic context, while the FW interface is
> > > > non
> > > > atomic.
> > > > Thus, 'ip' is not allowed to issue fw commands, so it will only
> > > > display
> > > > cached counters in the driver.
> > > >
> > > > Add a SW counter (mcast_packets) in the driver to count rx
> > > > multicast
> > > > packets. The counter also counts broadcast packets, as we
> > > > consider
> > > > it a
> > > > special case of multicast.
> > > > Use the counter value when calling "ip -s"/"ifconfig". Display
> > > > the
> > > > new
> > > > counter when calling "ethtool -S", and add a matching counter
> > > > (mcast_bytes) for completeness.
> > >
> > > What is the problem that is being solved here exactly?
> > >
> > > Device counts mcast wrong / unsuitably?
> > >
> >
> > To read mcast counter we need to execute FW command which is
> > blocking,
> > we can't block in atomic context .ndo_get_stats64 :( .. we have to
> > count in SW.
> >
> > the previous approach wasn't accurate as we read the mcast counter
> > in a
> > background thread triggered by the previous read.. so we were off
> > by
> > the interval between two reads.
>
> And that's bad enough to cause trouble? What's the worst case time
> delta you're seeing?
>
Depends on the user frequency to read stats,
if you read stats once every 5 minutes then mcast stats are off by 5
minutes..
Just thinking out loud, is it ok of we busy loop and wait for FW
response for mcast stats commands ?
In ethtool -S though, they are accurate since we grab them on the spot
from FW.
> > > > Fixes: f62b8bb8f2d3 ("net/mlx5: Extend mlx5_core to support
> > > > ConnectX-4 Ethernet functionality")
> > > > Signed-off-by: Ron Diskin <ro...@mellanox.com>
> > > > Reviewed-by: Tariq Toukan <tar...@mellanox.com>
> > > > Signed-off-by: Saeed Mahameed <sae...@mellanox.com>
