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    SubjectRe: [PATCH net-next v1 0/9] forcedeth: stats & debug enhancements
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    On Wed, 2011-11-09 at 14:09 -0800, David Decotigny wrote:
    > These changes implement the ndo_get_stats64 API and add a few more
    > stats and debugging features for forcedeth. They also ensure that
    > stats updates are correct in SMP systems, 32 or 64-bits.
    >
    > Regarding the "implement ndo_get_stats64() API" patch, I'm not sure
    > I'm using the right way to protect the 64b stats. Ideally, I would
    > like them to be non-blocking (u64_stats_sync.h), but as there are
    > several sources for updates, I don't think I can do without locking or
    > per-CPU stats.

    The important thing is that the fast path remains fast, and I think
    you've achieved that (due to patch 4/9). The data path doesn't have to
    acquire the stats lock and it only has to use atomic operations in some
    error cases.

    > Would per-CPU stats be better here (note: I expect the
    > contention on netdev_priv(dev)->stats_lock to be _VERY_ low)?
    [...]

    Only queue-less software devices should maintain per-CPU stats. For any
    device with queues, servicing of each queue must already be serialised
    and software stats can be maintained per-queue. In the single-queue
    case this means per-device.

    Ben.

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



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