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author | Eric Dumazet <eric.dumazet@gmail.com> | 2011-05-24 11:12:58 +0200 |
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committer | Thomas Gleixner <tglx@linutronix.de> | 2011-05-24 12:10:51 +0200 |
commit | 8af088710d1eb3c980e0ef3779c8d47f3f217b48 (patch) | |
tree | e122a2e65684f0a40d263ba73afe3d54a2c5993a /include/linux/posix-timers.h | |
parent | d762f4383100c2a87b1a3f2d678cd3b5425655b4 (diff) | |
download | linux-stable-8af088710d1eb3c980e0ef3779c8d47f3f217b48.tar.gz linux-stable-8af088710d1eb3c980e0ef3779c8d47f3f217b48.tar.bz2 linux-stable-8af088710d1eb3c980e0ef3779c8d47f3f217b48.zip |
posix-timers: RCU conversion
Ben Nagy reported a scalability problem with KVM/QEMU that hit very hard
a single spinlock (idr_lock) in posix-timers code, on its 48 core
machine.
Even on a 16 cpu machine (2x4x2), a single test can show 98% of cpu time
used in ticket_spin_lock, from lock_timer
Ref: http://www.spinics.net/lists/kvm/msg51526.html
Switching to RCU is quite easy, IDR being already RCU ready. idr_lock
should be locked only for an insert/delete, not a lookup.
Benchmark on a 2x4x2 machine, 16 processes calling timer_gettime().
Before :
real 1m18.669s
user 0m1.346s
sys 1m17.180s
After :
real 0m3.296s
user 0m1.366s
sys 0m1.926s
Reported-by: Ben Nagy <ben@iagu.net>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Tested-by: Ben Nagy <ben@iagu.net>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Avi Kivity <avi@redhat.com>
Cc: John Stultz <johnstul@us.ibm.com>
Cc: Richard Cochran <richard.cochran@omicron.at>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Diffstat (limited to 'include/linux/posix-timers.h')
-rw-r--r-- | include/linux/posix-timers.h | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/include/linux/posix-timers.h b/include/linux/posix-timers.h index 808227d40a64..959c14132f46 100644 --- a/include/linux/posix-timers.h +++ b/include/linux/posix-timers.h @@ -82,6 +82,7 @@ struct k_itimer { unsigned long expires; } mmtimer; struct alarm alarmtimer; + struct rcu_head rcu; } it; }; |