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charset="utf-8" The bypass flush decision logic is duplicated in rcu_nocb_try_bypass() and nocb_gp_wait() with similar conditions. This commit therefore extracts the functionality into a common helper function nocb_bypass_needs_flush() improving the code readability. A flush_faster parameter is added to controlling the flushing thresholds and timeouts. This design was in the original commit d1b222c6be1f ("rcu/nocb: Add bypass callback queueing") to avoid having the GP kthread aggressively flush the bypass queue. Reviewed-by: Frederic Weisbecker Signed-off-by: Joel Fernandes --- kernel/rcu/tree_nocb.h | 51 ++++++++++++++++++++++++++++++------------ 1 file changed, 37 insertions(+), 14 deletions(-) diff --git a/kernel/rcu/tree_nocb.h b/kernel/rcu/tree_nocb.h index d5e4d23090e8..1047b30cd46b 100644 --- a/kernel/rcu/tree_nocb.h +++ b/kernel/rcu/tree_nocb.h @@ -378,6 +378,38 @@ static void rcu_nocb_try_flush_bypass(struct rcu_data = *rdp, unsigned long j) WARN_ON_ONCE(!rcu_nocb_do_flush_bypass(rdp, NULL, j, false)); } =20 +/* + * Determine if the bypass queue needs to be flushed based on time and siz= e. + * For lazy-only bypass queues, use the lazy flush timeout; otherwise flush + * based on jiffy advancement. The flush_faster controls flush aggressiven= ess. + */ +static bool nocb_bypass_needs_flush(struct rcu_data *rdp, long bypass_ncbs, + long lazy_ncbs, unsigned long j, + bool flush_faster) +{ + bool bypass_is_lazy; + unsigned long bypass_first; + unsigned long flush_timeout; + long qhimark_thresh; + + if (!bypass_ncbs) + return false; + + qhimark_thresh =3D flush_faster ? qhimark : 2 * qhimark; + if (bypass_ncbs >=3D qhimark_thresh) + return true; + + bypass_first =3D READ_ONCE(rdp->nocb_bypass_first); + bypass_is_lazy =3D (bypass_ncbs =3D=3D lazy_ncbs); + + if (bypass_is_lazy) + flush_timeout =3D rcu_get_jiffies_lazy_flush(); + else + flush_timeout =3D flush_faster ? 0 : 1; + + return time_after(j, bypass_first + flush_timeout); +} + /* * See whether it is appropriate to use the ->nocb_bypass list in order * to control contention on ->nocb_lock. A limited number of direct @@ -404,7 +436,8 @@ static bool rcu_nocb_try_bypass(struct rcu_data *rdp, s= truct rcu_head *rhp, unsigned long cur_gp_seq; unsigned long j =3D jiffies; long ncbs =3D rcu_cblist_n_cbs(&rdp->nocb_bypass); - bool bypass_is_lazy =3D (ncbs =3D=3D READ_ONCE(rdp->lazy_len)); + long lazy_len =3D READ_ONCE(rdp->lazy_len); + bool bypass_is_lazy =3D (ncbs =3D=3D lazy_len); =20 lockdep_assert_irqs_disabled(); =20 @@ -456,10 +489,7 @@ static bool rcu_nocb_try_bypass(struct rcu_data *rdp, = struct rcu_head *rhp, =20 // If ->nocb_bypass has been used too long or is too full, // flush ->nocb_bypass to ->cblist. - if ((ncbs && !bypass_is_lazy && j !=3D READ_ONCE(rdp->nocb_bypass_first))= || - (ncbs && bypass_is_lazy && - (time_after(j, READ_ONCE(rdp->nocb_bypass_first) + rcu_get_jiffies_l= azy_flush()))) || - ncbs >=3D qhimark) { + if (nocb_bypass_needs_flush(rdp, ncbs, lazy_len, j, true)) { rcu_nocb_lock(rdp); *was_alldone =3D !rcu_segcblist_pend_cbs(&rdp->cblist); =20 @@ -673,15 +703,8 @@ static void nocb_gp_wait(struct rcu_data *my_rdp) bypass_ncbs =3D rcu_cblist_n_cbs(&rdp->nocb_bypass); lazy_ncbs =3D READ_ONCE(rdp->lazy_len); =20 - if (bypass_ncbs && (lazy_ncbs =3D=3D bypass_ncbs) && - (time_after(j, READ_ONCE(rdp->nocb_bypass_first) + rcu_get_jiffies_l= azy_flush()) || - bypass_ncbs > 2 * qhimark)) { - flush_bypass =3D true; - } else if (bypass_ncbs && (lazy_ncbs !=3D bypass_ncbs) && - (time_after(j, READ_ONCE(rdp->nocb_bypass_first) + 1) || - bypass_ncbs > 2 * qhimark)) { - flush_bypass =3D true; - } else if (!bypass_ncbs && rcu_segcblist_empty(&rdp->cblist)) { + flush_bypass =3D nocb_bypass_needs_flush(rdp, bypass_ncbs, lazy_ncbs, j,= false); + if (!flush_bypass && !bypass_ncbs && rcu_segcblist_empty(&rdp->cblist)) { rcu_nocb_unlock_irqrestore(rdp, flags); continue; /* No callbacks here, try next. */ } --=20 2.34.1