[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
[Qemu-devel] [PULL 40/45] rcu: optimize rcu_read_lock
From: |
Paolo Bonzini |
Subject: |
[Qemu-devel] [PULL 40/45] rcu: optimize rcu_read_lock |
Date: |
Thu, 17 Dec 2015 18:46:36 +0100 |
rcu_read_lock cannot change rcu_gp_ongoing from true to false
(the previous value of p_rcu_reader->ctr is zero), hence
there is no need to check p_rcu_reader->waiting and wake up
a concurrent synchronize_rcu.
While at it mark the wakeup as unlikely in rcu_read_unlock.
Reviewed-by: Wen Congyang <address@hidden>
Signed-off-by: Paolo Bonzini <address@hidden>
Message-Id: <address@hidden>
---
include/qemu/rcu.h | 6 +-----
1 file changed, 1 insertion(+), 5 deletions(-)
diff --git a/include/qemu/rcu.h b/include/qemu/rcu.h
index f6d1d56..7c7cca7 100644
--- a/include/qemu/rcu.h
+++ b/include/qemu/rcu.h
@@ -88,10 +88,6 @@ static inline void rcu_read_lock(void)
ctr = atomic_read(&rcu_gp_ctr);
atomic_xchg(&p_rcu_reader->ctr, ctr);
- if (atomic_read(&p_rcu_reader->waiting)) {
- atomic_set(&p_rcu_reader->waiting, false);
- qemu_event_set(&rcu_gp_event);
- }
}
static inline void rcu_read_unlock(void)
@@ -104,7 +100,7 @@ static inline void rcu_read_unlock(void)
}
atomic_xchg(&p_rcu_reader->ctr, 0);
- if (atomic_read(&p_rcu_reader->waiting)) {
+ if (unlikely(atomic_read(&p_rcu_reader->waiting))) {
atomic_set(&p_rcu_reader->waiting, false);
qemu_event_set(&rcu_gp_event);
}
--
2.5.0
- [Qemu-devel] [PULL 27/45] tricore: avoid "naked" qemu_log, (continued)
- [Qemu-devel] [PULL 27/45] tricore: avoid "naked" qemu_log, Paolo Bonzini, 2015/12/17
- [Qemu-devel] [PULL 25/45] s390x: avoid "naked" qemu_log, Paolo Bonzini, 2015/12/17
- [Qemu-devel] [PULL 26/45] ppc: cleanup logging, Paolo Bonzini, 2015/12/17
- [Qemu-devel] [PULL 29/45] user: introduce "-d page", Paolo Bonzini, 2015/12/17
- [Qemu-devel] [PULL 32/45] exec: always call qemu_get_ram_ptr within rcu_read_lock, Paolo Bonzini, 2015/12/17
- [Qemu-devel] [PULL 34/45] memory: reorder MemoryRegion fields, Paolo Bonzini, 2015/12/17
- [Qemu-devel] [PULL 31/45] linux-user: convert DEBUG_SIGNAL logging to tracepoints, Paolo Bonzini, 2015/12/17
- [Qemu-devel] [PULL 30/45] linux-user: avoid "naked" qemu_log, Paolo Bonzini, 2015/12/17
- [Qemu-devel] [PULL 28/45] xtensa: avoid "naked" qemu_log, Paolo Bonzini, 2015/12/17
- [Qemu-devel] [PULL 35/45] memory: avoid unnecessary object_ref/unref, Paolo Bonzini, 2015/12/17
- [Qemu-devel] [PULL 40/45] rcu: optimize rcu_read_lock,
Paolo Bonzini <=
- [Qemu-devel] [PULL 37/45] memory: extract first iteration of address_space_read and address_space_write, Paolo Bonzini, 2015/12/17
- [Qemu-devel] [PULL 41/45] target-i386: kvm: clear unusable segments' flags in migration, Paolo Bonzini, 2015/12/17
- [Qemu-devel] [PULL 43/45] scsi: always call notifier on async cancellation, Paolo Bonzini, 2015/12/17
- [Qemu-devel] [PULL 44/45] coverity: Model g_poll(), Paolo Bonzini, 2015/12/17
- [Qemu-devel] [PULL 33/45] exec: make qemu_ram_ptr_length more similar to qemu_get_ram_ptr, Paolo Bonzini, 2015/12/17
- [Qemu-devel] [PULL 36/45] memory: split address_space_read and address_space_write, Paolo Bonzini, 2015/12/17
- [Qemu-devel] [PULL 38/45] memory: inline a few small accessors, Paolo Bonzini, 2015/12/17