diff options
| author | Paolo Abeni <pabeni@redhat.com> | 2018-05-15 11:50:31 +0300 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2018-05-16 19:26:25 +0300 |
| commit | 32f7b44d0f5661044fcfa84e9ad402ed9d759107 (patch) | |
| tree | d2453e21a4187e32c9da74a25bbfee4446e725b5 /include/net/sch_generic.h | |
| parent | 5a63f77af7d69deb02a92b60d61141fe687997f8 (diff) | |
| download | linux-32f7b44d0f5661044fcfa84e9ad402ed9d759107.tar.xz | |
sched: manipulate __QDISC_STATE_RUNNING in qdisc_run_* helpers
Currently NOLOCK qdiscs pay a measurable overhead to atomically
manipulate the __QDISC_STATE_RUNNING. Such bit is flipped twice per
packet in the uncontended scenario with packet rate below the
line rate: on packed dequeue and on the next, failing dequeue attempt.
This changeset moves the bit manipulation into the qdisc_run_{begin,end}
helpers, so that the bit is now flipped only once per packet, with
measurable performance improvement in the uncontended scenario.
This also allows simplifying the qdisc teardown code path - since
qdisc_is_running() is now effective for each qdisc type - and avoid a
possible race between qdisc_run() and dev_deactivate_many(), as now
the some_qdisc_is_busy() can properly detect NOLOCK qdiscs being busy
dequeuing packets.
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'include/net/sch_generic.h')
| -rw-r--r-- | include/net/sch_generic.h | 10 |
1 files changed, 9 insertions, 1 deletions
diff --git a/include/net/sch_generic.h b/include/net/sch_generic.h index 5154c8300262..4d2b37226e75 100644 --- a/include/net/sch_generic.h +++ b/include/net/sch_generic.h @@ -113,13 +113,19 @@ static inline void qdisc_refcount_inc(struct Qdisc *qdisc) static inline bool qdisc_is_running(const struct Qdisc *qdisc) { + if (qdisc->flags & TCQ_F_NOLOCK) + return test_bit(__QDISC_STATE_RUNNING, &qdisc->state); return (raw_read_seqcount(&qdisc->running) & 1) ? true : false; } static inline bool qdisc_run_begin(struct Qdisc *qdisc) { - if (qdisc_is_running(qdisc)) + if (qdisc->flags & TCQ_F_NOLOCK) { + if (test_and_set_bit(__QDISC_STATE_RUNNING, &qdisc->state)) + return false; + } else if (qdisc_is_running(qdisc)) { return false; + } /* Variant of write_seqcount_begin() telling lockdep a trylock * was attempted. */ @@ -131,6 +137,8 @@ static inline bool qdisc_run_begin(struct Qdisc *qdisc) static inline void qdisc_run_end(struct Qdisc *qdisc) { write_seqcount_end(&qdisc->running); + if (qdisc->flags & TCQ_F_NOLOCK) + clear_bit(__QDISC_STATE_RUNNING, &qdisc->state); } static inline bool qdisc_may_bulk(const struct Qdisc *qdisc) |