rcu: Avoid waking up CPUs having only kfree_rcu() callbacks
When CONFIG_RCU_FAST_NO_HZ is enabled, RCU will allow a given CPU to
enter dyntick-idle mode even if it still has RCU callbacks queued.
RCU avoids system hangs in this case by scheduling a timer for several
jiffies in the future. However, if all of the callbacks on that CPU
are from kfree_rcu(), there is no reason to wake the CPU up, as it is
not a problem to defer freeing of memory.
This commit therefore tracks the number of callbacks on a given CPU
that are from kfree_rcu(), and avoids scheduling the timer if all of
a given CPU's callbacks are from kfree_rcu().
Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
diff --git a/kernel/rcutree_trace.c b/kernel/rcutree_trace.c
index 654cfe6..db0987c 100644
--- a/kernel/rcutree_trace.c
+++ b/kernel/rcutree_trace.c
@@ -73,8 +73,8 @@
rdp->dynticks->dynticks_nmi_nesting,
rdp->dynticks_fqs);
seq_printf(m, " of=%lu ri=%lu", rdp->offline_fqs, rdp->resched_ipi);
- seq_printf(m, " ql=%ld qs=%c%c%c%c",
- rdp->qlen,
+ seq_printf(m, " ql=%ld/%ld qs=%c%c%c%c",
+ rdp->qlen_lazy, rdp->qlen,
".N"[rdp->nxttail[RCU_NEXT_READY_TAIL] !=
rdp->nxttail[RCU_NEXT_TAIL]],
".R"[rdp->nxttail[RCU_WAIT_TAIL] !=
@@ -145,7 +145,7 @@
rdp->dynticks->dynticks_nmi_nesting,
rdp->dynticks_fqs);
seq_printf(m, ",%lu,%lu", rdp->offline_fqs, rdp->resched_ipi);
- seq_printf(m, ",%ld,\"%c%c%c%c\"", rdp->qlen,
+ seq_printf(m, ",%ld,%ld,\"%c%c%c%c\"", rdp->qlen_lazy, rdp->qlen,
".N"[rdp->nxttail[RCU_NEXT_READY_TAIL] !=
rdp->nxttail[RCU_NEXT_TAIL]],
".R"[rdp->nxttail[RCU_WAIT_TAIL] !=
@@ -168,7 +168,7 @@
{
seq_puts(m, "\"CPU\",\"Online?\",\"c\",\"g\",\"pq\",\"pgp\",\"pq\",");
seq_puts(m, "\"dt\",\"dt nesting\",\"dt NMI nesting\",\"df\",");
- seq_puts(m, "\"of\",\"ri\",\"ql\",\"qs\"");
+ seq_puts(m, "\"of\",\"ri\",\"qll\",\"ql\",\"qs\"");
#ifdef CONFIG_RCU_BOOST
seq_puts(m, "\"kt\",\"ktl\"");
#endif /* #ifdef CONFIG_RCU_BOOST */