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Commit 4605c014 authored by Paul E. McKenney's avatar Paul E. McKenney
Browse files

rcu: Adjust debugfs tracing for kthread-based quiescent-state forcing 



Moving quiescent-state forcing into a kthread dispenses with the need
for the ->n_rp_need_fqs field, so this commit removes it.

Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: default avatarJosh Triplett <josh@joshtriplett.org>
parent b4be093f

Documentation/RCU/trace.txt

+16 −27
Original line number Diff line number Diff line
@@ -333,23 +333,23 @@ o Each element of the form "1/1 0:127 ^0" represents one struct 
The output of "cat rcu/rcu_pending" looks as follows:



rcu_sched:

  0 np=255892 qsp=53936 rpq=85 cbr=0 cng=14417 gpc=10033 gps=24320 nf=6445 nn=146741

  1 np=261224 qsp=54638 rpq=33 cbr=0 cng=25723 gpc=16310 gps=2849 nf=5912 nn=155792

  2 np=237496 qsp=49664 rpq=23 cbr=0 cng=2762 gpc=45478 gps=1762 nf=1201 nn=136629

  3 np=236249 qsp=48766 rpq=98 cbr=0 cng=286 gpc=48049 gps=1218 nf=207 nn=137723

  4 np=221310 qsp=46850 rpq=7 cbr=0 cng=26 gpc=43161 gps=4634 nf=3529 nn=123110

  5 np=237332 qsp=48449 rpq=9 cbr=0 cng=54 gpc=47920 gps=3252 nf=201 nn=137456

  6 np=219995 qsp=46718 rpq=12 cbr=0 cng=50 gpc=42098 gps=6093 nf=4202 nn=120834

  7 np=249893 qsp=49390 rpq=42 cbr=0 cng=72 gpc=38400 gps=17102 nf=41 nn=144888

  0 np=255892 qsp=53936 rpq=85 cbr=0 cng=14417 gpc=10033 gps=24320 nn=146741

  1 np=261224 qsp=54638 rpq=33 cbr=0 cng=25723 gpc=16310 gps=2849 nn=155792

  2 np=237496 qsp=49664 rpq=23 cbr=0 cng=2762 gpc=45478 gps=1762 nn=136629

  3 np=236249 qsp=48766 rpq=98 cbr=0 cng=286 gpc=48049 gps=1218 nn=137723

  4 np=221310 qsp=46850 rpq=7 cbr=0 cng=26 gpc=43161 gps=4634 nn=123110

  5 np=237332 qsp=48449 rpq=9 cbr=0 cng=54 gpc=47920 gps=3252 nn=137456

  6 np=219995 qsp=46718 rpq=12 cbr=0 cng=50 gpc=42098 gps=6093 nn=120834

  7 np=249893 qsp=49390 rpq=42 cbr=0 cng=72 gpc=38400 gps=17102 nn=144888

rcu_bh:

  0 np=146741 qsp=1419 rpq=6 cbr=0 cng=6 gpc=0 gps=0 nf=2 nn=145314

  1 np=155792 qsp=12597 rpq=3 cbr=0 cng=0 gpc=4 gps=8 nf=3 nn=143180

  2 np=136629 qsp=18680 rpq=1 cbr=0 cng=0 gpc=7 gps=6 nf=0 nn=117936

  3 np=137723 qsp=2843 rpq=0 cbr=0 cng=0 gpc=10 gps=7 nf=0 nn=134863

  4 np=123110 qsp=12433 rpq=0 cbr=0 cng=0 gpc=4 gps=2 nf=0 nn=110671

  5 np=137456 qsp=4210 rpq=1 cbr=0 cng=0 gpc=6 gps=5 nf=0 nn=133235

  6 np=120834 qsp=9902 rpq=2 cbr=0 cng=0 gpc=6 gps=3 nf=2 nn=110921

  7 np=144888 qsp=26336 rpq=0 cbr=0 cng=0 gpc=8 gps=2 nf=0 nn=118542

  0 np=146741 qsp=1419 rpq=6 cbr=0 cng=6 gpc=0 gps=0 nn=145314

  1 np=155792 qsp=12597 rpq=3 cbr=0 cng=0 gpc=4 gps=8 nn=143180

  2 np=136629 qsp=18680 rpq=1 cbr=0 cng=0 gpc=7 gps=6 nn=117936

  3 np=137723 qsp=2843 rpq=0 cbr=0 cng=0 gpc=10 gps=7 nn=134863

  4 np=123110 qsp=12433 rpq=0 cbr=0 cng=0 gpc=4 gps=2 nn=110671

  5 np=137456 qsp=4210 rpq=1 cbr=0 cng=0 gpc=6 gps=5 nn=133235

  6 np=120834 qsp=9902 rpq=2 cbr=0 cng=0 gpc=6 gps=3 nn=110921

  7 np=144888 qsp=26336 rpq=0 cbr=0 cng=0 gpc=8 gps=2 nn=118542



As always, this is once again split into "rcu_sched" and "rcu_bh"

portions, with CONFIG_TREE_PREEMPT_RCU kernels having an additional
@@ -377,17 +377,6 @@ o "gpc" is the number of times that an old grace period had 
o	"gps" is the number of times that a new grace period had started,

	but this CPU was not yet aware of it.



o	"nf" is the number of times that this CPU suspected that the

	current grace period had run for too long, and thus needed to

	be forced.



	Please note that "forcing" consists of sending resched IPIs

	to holdout CPUs.  If that CPU really still is in an old RCU

	read-side critical section, then we really do have to wait for it.

	The assumption behing "forcing" is that the CPU is not still in

	an old RCU read-side critical section, but has not yet responded

	for some other reason.



o	"nn" is the number of times that this CPU needed nothing.  Alert

	readers will note that the rcu "nn" number for a given CPU very

	closely matches the rcu_bh "np" number for that same CPU.  This

kernel/rcutree.h

+0 −1
Original line number Diff line number Diff line
@@ -312,7 +312,6 @@ struct rcu_data { 
	unsigned long n_rp_cpu_needs_gp;

	unsigned long n_rp_gp_completed;

	unsigned long n_rp_gp_started;

	unsigned long n_rp_need_fqs;

	unsigned long n_rp_need_nothing;



	/* 6) _rcu_barrier() and OOM callbacks. */

kernel/rcutree_trace.c

+1 −2
Original line number Diff line number Diff line
@@ -386,10 +386,9 @@ static void print_one_rcu_pending(struct seq_file *m, struct rcu_data *rdp) 
		   rdp->n_rp_report_qs,

		   rdp->n_rp_cb_ready,

		   rdp->n_rp_cpu_needs_gp);

	seq_printf(m, "gpc=%ld gps=%ld nf=%ld nn=%ld\n",

	seq_printf(m, "gpc=%ld gps=%ld nn=%ld\n",

		   rdp->n_rp_gp_completed,

		   rdp->n_rp_gp_started,

		   rdp->n_rp_need_fqs,

		   rdp->n_rp_need_nothing);

}