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net: busy-poll: use ktime_get_ns() instead of local_clock()

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Typically, busy-polling durations are below 100 usec.

When/if the busy-poller thread migrates to another cpu,
local_clock() can be off by +/-2msec or more for small
values of HZ, depending on the platform.

Use ktimer_get_ns() to ensure deterministic behavior,
which is the whole point of busy-polling.

Fixes: 0602129286 ("net: add low latency socket poll")
Fixes: 9a3c71aa80 ("net: convert low latency sockets to sched_clock()")
Fixes: 3708983452 ("sched, net: Fixup busy_loop_us_clock()")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Mina Almasry <almasrymina@google.com>
Cc: Willem de Bruijn <willemb@google.com>
Reviewed-by: Joe Damato <jdamato@fastly.com>
Link: https://patch.msgid.link/20240827114916.223377-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Eric Dumazet 2024-08-27 11:49:16 +00:00 committed by Jakub Kicinski
parent 41901c227e
commit 0870b0d8b3
1 changed files with 1 additions and 1 deletions
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2
include/net/busy_poll.h
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@ -68,7 +68,7 @@ static inline bool sk_can_busy_loop(struct sock *sk)
static inline unsigned long busy_loop_current_time(void)
{
#ifdef CONFIG_NET_RX_BUSY_POLL
return (unsigned long)(local_clock() >> 10);
return (unsigned long)(ktime_get_ns() >> 10);
#else
return 0;
#endif