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Commit 80ed87c8 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
Browse files

sched/wait: Introduce TASK_NOLOAD and TASK_IDLE 



Currently people use TASK_INTERRUPTIBLE to idle kthreads and wait for
'work' because TASK_UNINTERRUPTIBLE contributes to the loadavg. Having
all idle kthreads contribute to the loadavg is somewhat silly.

Now mostly this works OK, because kthreads have all their signals
masked. However there's a few sites where this is causing problems and
TASK_UNINTERRUPTIBLE should be used, except for that loadavg issue.

This patch adds TASK_NOLOAD which, when combined with
TASK_UNINTERRUPTIBLE avoids the loadavg accounting.

As most of imagined usage sites are loops where a thread wants to
idle, waiting for work, a helper TASK_IDLE is introduced.

Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Julian Anastasov <ja@ssi.bg>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: NeilBrown <neilb@suse.de>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 8222dbe2

include/linux/sched.h

+7 −3
Original line number Diff line number Diff line
@@ -218,9 +218,10 @@ print_cfs_rq(struct seq_file *m, int cpu, struct cfs_rq *cfs_rq); 
#define TASK_WAKEKILL		128

#define TASK_WAKING		256

#define TASK_PARKED		512

#define TASK_STATE_MAX		1024

#define TASK_NOLOAD		1024

#define TASK_STATE_MAX		2048



#define TASK_STATE_TO_CHAR_STR "RSDTtXZxKWP"

#define TASK_STATE_TO_CHAR_STR "RSDTtXZxKWPN"



extern char ___assert_task_state[1 - 2*!!(

		sizeof(TASK_STATE_TO_CHAR_STR)-1 != ilog2(TASK_STATE_MAX)+1)];
@@ -230,6 +231,8 @@ extern char ___assert_task_state[1 - 2*!!( 
#define TASK_STOPPED		(TASK_WAKEKILL | __TASK_STOPPED)

#define TASK_TRACED		(TASK_WAKEKILL | __TASK_TRACED)



#define TASK_IDLE		(TASK_UNINTERRUPTIBLE | TASK_NOLOAD)



/* Convenience macros for the sake of wake_up */

#define TASK_NORMAL		(TASK_INTERRUPTIBLE | TASK_UNINTERRUPTIBLE)

#define TASK_ALL		(TASK_NORMAL | __TASK_STOPPED | __TASK_TRACED)
@@ -245,7 +248,8 @@ extern char ___assert_task_state[1 - 2*!!( 
			((task->state & (__TASK_STOPPED | __TASK_TRACED)) != 0)

#define task_contributes_to_load(task)	\

				((task->state & TASK_UNINTERRUPTIBLE) != 0 && \

				 (task->flags & PF_FROZEN) == 0)

				 (task->flags & PF_FROZEN) == 0 && \

				 (task->state & TASK_NOLOAD) == 0)



#ifdef CONFIG_DEBUG_ATOMIC_SLEEP

include/trace/events/sched.h

+2 −1
Original line number Diff line number Diff line
@@ -147,7 +147,8 @@ TRACE_EVENT(sched_switch, 
		  __print_flags(__entry->prev_state & (TASK_STATE_MAX-1), "|",

				{ 1, "S"} , { 2, "D" }, { 4, "T" }, { 8, "t" },

				{ 16, "Z" }, { 32, "X" }, { 64, "x" },

				{ 128, "K" }, { 256, "W" }, { 512, "P" }) : "R",

				{ 128, "K" }, { 256, "W" }, { 512, "P" },

				{ 1024, "N" }) : "R",

		__entry->prev_state & TASK_STATE_MAX ? "+" : "",

		__entry->next_comm, __entry->next_pid, __entry->next_prio)

);