STRUCT TICK_SCHED(9)

✨ NAME ✨

struct tick_sched — bestie, this is the whole sched tick emulation + no idle tick control/stats situation, and it's lowkey the main character of timekeeping 🕰️💅

Oh and hey, this page lives in the Kernel API Manual — iconic company, no cap.

🌸 SYNOPSIS 🌸

struct tick_sched {
    unsigned long                   flags;
    unsigned int                    stalled_jiffies;
    unsigned long                   last_tick_jiffies;
    struct hrtimer                  sched_timer;
    ktime_t last_tick;
    ktime_t next_tick;
    ktime_t idle_waketime;
    unsigned int                    got_idle_tick;
    ktime_t idle_entrytime;
    unsigned long                   last_jiffies;
    u64 timer_expires_base;
    u64 timer_expires;
    u64 next_timer;
    ktime_t idle_expires;
    unsigned long                   idle_calls;
    unsigned long                   idle_sleeps;
    atomic_t tick_dep_mask;
    unsigned long                   check_clocks;
};

💜 Members 💜

Ok so let's go through every single one of these fields, because they ALL matter and I refuse to skip a single one 🫶

• flags — the state flags, gathering up all the TS_FLAG_* features together. It's giving "flags shelf" energy ✨
• stalled_jiffies — how many stalled jiffies got detected across ticks. Like, the tally of times things got stuck 😭
• last_tick_jiffies — the value of jiffies that was seen on the last tick. Just a lil snapshot 📸
• sched_timer — an hrtimer used to schedule the periodic tick in high resolution mode. Fancy timing, periodt 🔥
• last_tick — stores the last tick expiry time whenever the tick timer gets modified for nohz sleeps. Bestie, this one is necessary — it's literally needed so the tick timer operation can resume in the timeline when the CPU comes back from nohz sleep 🧚
• next_tick — the next tick that's gonna fire when we're in dynticks mode ⏭️
• idle_waketime — the time when the idle got interrupted 🙈
• got_idle_tick — the tick timer function has run with inidle set ✔️
• idle_entrytime — the time when the idle call was entered 🚪
• last_jiffies — the base jiffies snapshot from when the next event was last computed 🫧
• timer_expires_base — the base time, clock monotonic, for timer_expires 🕰️
• timer_expires — the anticipated timer expiration time (this is in case the sched tick is stopped) ⏳
• next_timer — expiry time of the next expiring timer, and ngl this one is for debugging purposes only 🐛
• idle_expires — the next tick in idle, also for debugging purposes only 🐛
• idle_calls — the total number of idle calls 🔢
• idle_sleeps — number of idle calls where the sched tick was stopped 😴
• tick_dep_mask — the tick dependency mask; it's set if someone needs the tick 👑
• check_clocks — the notification mechanism about clocksource changes 🔔

Fr fr, those last two "debugging purpose only" fields are exactly what they say — don't go building your whole arch on them, bestie 💀

🦋 SEE ALSO 🦋

• Kernel file ./kernel/time/tick-sched.h — go read it, iykyk 📖

✨ That's the whole vibe check, bestie ✨ This page ships from ./kernel/time (that's the source/version, mwah 💋) and it's dated October 2026. Slay, bye! 🎀💖