The patch titled
rcu: simplify/improve batch tuning
has been added to the -mm tree. Its filename is
rcu-simplify-improve-batch-tuning.patch
See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
------------------------------------------------------
Subject: rcu: simplify/improve batch tuning
From: Oleg Nesterov <oleg@xxxxxxxxxx>
Kill a hard-to-calculate 'rsinterval' boot parameter and per-cpu
rcu_data.last_rs_qlen. Instead, it adds adds a flag rcu_ctrlblk.signaled,
which records the fact that one of CPUs has sent a resched IPI since the
last rcu_start_batch().
Roughly speaking, we need two rcu_start_batch()s in order to move callbacks
from ->nxtlist to ->donelist. This means that when ->qlen exceeds qhimark
and continues to grow, we should send a resched IPI, and then do it again
after we gone through a quiescent state.
On the other hand, if it was already sent, we don't need to do it again
when another CPU detects overflow of the queue.
Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
Acked-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxx>
---
Documentation/kernel-parameters.txt | 4 ----
include/linux/rcupdate.h | 5 ++---
kernel/rcupdate.c | 11 +++--------
3 files changed, 5 insertions(+), 15 deletions(-)
diff -puN Documentation/kernel-parameters.txt~rcu-simplify-improve-batch-tuning Documentation/kernel-parameters.txt
--- a/Documentation/kernel-parameters.txt~rcu-simplify-improve-batch-tuning
+++ a/Documentation/kernel-parameters.txt
@@ -1351,10 +1351,6 @@ and is between 256 and 4096 characters.
rcu.qlowmark= [KNL,BOOT] Set threshold of queued
RCU callbacks below which batch limiting is re-enabled.
- rcu.rsinterval= [KNL,BOOT,SMP] Set the number of additional
- RCU callbacks to queued before forcing reschedule
- on all cpus.
-
rdinit= [KNL]
Format: <full_path>
Run specified binary instead of /init from the ramdisk,
diff -puN include/linux/rcupdate.h~rcu-simplify-improve-batch-tuning include/linux/rcupdate.h
--- a/include/linux/rcupdate.h~rcu-simplify-improve-batch-tuning
+++ a/include/linux/rcupdate.h
@@ -66,6 +66,8 @@ struct rcu_ctrlblk {
long completed; /* Number of the last completed batch */
int next_pending; /* Is the next batch already waiting? */
+ int signaled;
+
spinlock_t lock ____cacheline_internodealigned_in_smp;
cpumask_t cpumask; /* CPUs that need to switch in order */
/* for current batch to proceed. */
@@ -106,9 +108,6 @@ struct rcu_data {
long blimit; /* Upper limit on a processed batch */
int cpu;
struct rcu_head barrier;
-#ifdef CONFIG_SMP
- long last_rs_qlen; /* qlen during the last resched */
-#endif
};
DECLARE_PER_CPU(struct rcu_data, rcu_data);
diff -puN kernel/rcupdate.c~rcu-simplify-improve-batch-tuning kernel/rcupdate.c
--- a/kernel/rcupdate.c~rcu-simplify-improve-batch-tuning
+++ a/kernel/rcupdate.c
@@ -71,9 +71,6 @@ static DEFINE_PER_CPU(struct tasklet_str
static int blimit = 10;
static int qhimark = 10000;
static int qlowmark = 100;
-#ifdef CONFIG_SMP
-static int rsinterval = 1000;
-#endif
static atomic_t rcu_barrier_cpu_count;
static DEFINE_MUTEX(rcu_barrier_mutex);
@@ -86,8 +83,8 @@ static void force_quiescent_state(struct
int cpu;
cpumask_t cpumask;
set_need_resched();
- if (unlikely(rdp->qlen - rdp->last_rs_qlen > rsinterval)) {
- rdp->last_rs_qlen = rdp->qlen;
+ if (unlikely(!rcp->signaled)) {
+ rcp->signaled = 1;
/*
* Don't send IPI to itself. With irqs disabled,
* rdp->cpu is the current cpu.
@@ -297,6 +294,7 @@ static void rcu_start_batch(struct rcu_c
smp_mb();
cpus_andnot(rcp->cpumask, cpu_online_map, nohz_cpu_mask);
+ rcp->signaled = 0;
}
}
@@ -624,9 +622,6 @@ void synchronize_rcu(void)
module_param(blimit, int, 0);
module_param(qhimark, int, 0);
module_param(qlowmark, int, 0);
-#ifdef CONFIG_SMP
-module_param(rsinterval, int, 0);
-#endif
EXPORT_SYMBOL_GPL(rcu_batches_completed);
EXPORT_SYMBOL_GPL(rcu_batches_completed_bh);
EXPORT_SYMBOL_GPL(call_rcu);
_
Patches currently in -mm which might be from oleg@xxxxxxxxxx are
git-block.patch
pid-implement-transfer_pid-and-use-it-to-simplify-de_thread.patch
pid-remove-temporary-debug-code-in-attach_pid.patch
rtmutex-clean-up-and-remove-some-extra-spinlocks.patch
rtmutex-clean-up-and-remove-some-extra-spinlocks-more.patch
elf_core_dump-dont-take-tasklist_lock.patch
elf_fdpic_core_dump-dont-take-tasklist_lock.patch
has_stopped_jobs-cleanup.patch
__dequeue_signal-cleanup.patch
do_sched_setscheduler-dont-take-tasklist_lock.patch
introduce-is_rt_policy-helper.patch
sched_setscheduler-fix-policy-checks.patch
reparent_to_init-use-has_rt_policy.patch
copy_process-cosmetic-ioprio-tweak.patch
futex_find_get_task-dont-take-tasklist_lock.patch
sys_get_robust_list-dont-take-tasklist_lock.patch
set-exit_dead-state-in-do_exit-not-in-schedule.patch
kill-pf_dead-flag.patch
introduce-task_dead-state.patch
select_bad_process-kill-a-bogus-pf_dead-task_dead-check.patch
select_bad_process-cleanup-releasing-check.patch
oom_kill_task-cleanup-mm-checks.patch
audit-accounting-tty-locking.patch
proc-readdir-race-fix-take-3-race-fix.patch
simplify-pid-iterators.patch
rcu-simplify-improve-batch-tuning.patch
pidhash-temporary-debug-checks.patch
-
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