Messages in this thread | | | Subject | Re: [RFC] time: xtime_lock is held too long | From | Eric Dumazet <> | Date | Fri, 06 May 2011 19:42:47 +0200 |
| |
Le vendredi 06 mai 2011 à 18:59 +0200, Andi Kleen a écrit :
> If you have a better way to make it faster please share it.
Ideally we could use RCU :)
Have whatever state hold in one structure (possibly big, it doesnt matter) and switch pointer in writer once everything is setup in new structure.
struct { struct timespec xtime; struct timespec wall_to_monotonic; ... } time_keep_blob;
struct time_keep_blob __rcu *xtime_cur;
ktime_t ktime_get(void) { const struct time_keep_blob *xp; s64 secs, nsecs;
rcu_read_lock(); xp = rcu_dereference(xtime_cur); secs = xp->xtime.tv_sec + xp->wall_to_monotonic.tv_sec; nsecs = xp->xtime.tv_nsec + xp->wall_to_monotonic.tv_nsec; nsecs += timekeeping_get_ns(xp); rcu_read_unlock();
return ktime_add_ns(ktime_set(secs, 0), nsecs); }
I dont know timekeeping details, maybe its necessary to loop if xtime_cur changes :
ktime_t ktime_get(void) { const struct time_keep_blob *xp; s64 secs, nsecs;
rcu_read_lock(); do { xp = rcu_dereference(xtime_cur); secs = xp->xtime.tv_sec + xp->wall_to_monotonic.tv_sec; nsecs = xp->xtime.tv_nsec + xp->wall_to_monotonic.tv_nsec; nsecs += timekeeping_get_ns(xp); } while (rcu_dereference(xtime_cur) != xp); rcu_read_unlock(); return ktime_add_ns(ktime_set(secs, 0), nsecs); }
-- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |