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posix-cpu-timers: Utilize timerqueue for storage

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Using a linear O(N) search for timer insertion affects execution time and
D-cache footprint badly with a larger number of timers.

Switch the storage to a timerqueue which is already used for hrtimers and
alarmtimers. It does not affect the size of struct k_itimer as it.alarm is
still larger.

The extra list head for the expiry list will go away later once the expiry
is moved into task work context.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://lkml.kernel.org/r/alpine.DEB.2.21.1908272129220.1939@nanos.tec.linutronix.de
This commit is contained in:
Thomas Gleixner 2019-08-27 21:31:02 +02:00
parent 244d49e306
commit 60bda037f1
3 changed files with 152 additions and 106 deletions
Download patch file Download diff file Expand all files Collapse all files

65
include/linux/posix-timers.h
View file

@ -5,17 +5,11 @@
#include <linux/spinlock.h>
#include <linux/list.h>
#include <linux/alarmtimer.h>
#include <linux/timerqueue.h>
struct kernel_siginfo;
struct task_struct;
struct cpu_timer_list {
struct list_head entry;
u64 expires;
struct task_struct *task;
int firing;
};
/*
* Bit fields within a clockid:
*
@ -64,14 +58,58 @@ static inline int clockid_to_fd(const clockid_t clk)
#ifdef CONFIG_POSIX_TIMERS
/**
* cpu_timer - Posix CPU timer representation for k_itimer
* @node: timerqueue node to queue in the task/sig
* @head: timerqueue head on which this timer is queued
* @task: Pointer to target task
* @elist: List head for the expiry list
* @firing: Timer is currently firing
*/
struct cpu_timer {
struct timerqueue_node node;
struct timerqueue_head *head;
struct task_struct *task;
struct list_head elist;
int firing;
};
static inline bool cpu_timer_requeue(struct cpu_timer *ctmr)
{
return timerqueue_add(ctmr->head, &ctmr->node);
}
static inline bool cpu_timer_enqueue(struct timerqueue_head *head,
struct cpu_timer *ctmr)
{
ctmr->head = head;
return timerqueue_add(head, &ctmr->node);
}
static inline void cpu_timer_dequeue(struct cpu_timer *ctmr)
{
if (!RB_EMPTY_NODE(&ctmr->node.node))
timerqueue_del(ctmr->head, &ctmr->node);
}
static inline u64 cpu_timer_getexpires(struct cpu_timer *ctmr)
{
return ctmr->node.expires;
}
static inline void cpu_timer_setexpires(struct cpu_timer *ctmr, u64 exp)
{
ctmr->node.expires = exp;
}
/**
* posix_cputimer_base - Container per posix CPU clock
* @nextevt: Earliest-expiration cache
* @cpu_timers: List heads to queue posix CPU timers
* @tqhead: timerqueue head for cpu_timers
*/
struct posix_cputimer_base {
u64 nextevt;
struct list_head cpu_timers;
struct timerqueue_head tqhead;
};
/**
@ -92,14 +130,10 @@ struct posix_cputimers {
static inline void posix_cputimers_init(struct posix_cputimers *pct)
{
pct->timers_active = 0;
pct->expiry_active = 0;
memset(pct, 0, sizeof(*pct));
pct->bases[0].nextevt = U64_MAX;
pct->bases[1].nextevt = U64_MAX;
pct->bases[2].nextevt = U64_MAX;
INIT_LIST_HEAD(&pct->bases[0].cpu_timers);
INIT_LIST_HEAD(&pct->bases[1].cpu_timers);
INIT_LIST_HEAD(&pct->bases[2].cpu_timers);
}
void posix_cputimers_group_init(struct posix_cputimers *pct, u64 cpu_limit);
@ -113,7 +147,6 @@ static inline void posix_cputimers_rt_watchdog(struct posix_cputimers *pct,
/* Init task static initializer */
#define INIT_CPU_TIMERBASE(b) { \
.nextevt = U64_MAX, \
.cpu_timers = LIST_HEAD_INIT(b.cpu_timers), \
}
#define INIT_CPU_TIMERBASES(b) { \
@ -182,7 +215,7 @@ struct k_itimer {
struct {
struct hrtimer timer;
} real;
struct cpu_timer_list cpu;
struct cpu_timer cpu;
struct {
struct alarm alarmtimer;
} alarm;