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softmmu/cpus: Check if the cpu work list is empty atomically 

Instead of taking the lock of the cpu work list in order to check if it's
empty, we can just read the head pointer atomically. This decreases
cpu_work_list_empty's share from 5% to 1.3% in a profile of icount-enabled
aarch64-softmmu.

Signed-off-by: Idan Horowitz <idan.horowitz@gmail.com>
Message-Id: <20220114004358.299534-1-idan.horowitz@gmail.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
This commit is contained in:
Idan Horowitz 2022-01-14 02:43:57 +02:00 committed by Richard Henderson
parent cfc2a2d69d
commit 25e82fb769
1 changed files with 1 additions and 6 deletions
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softmmu/cpus.c
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@ -73,12 +73,7 @@ bool cpu_is_stopped(CPUState *cpu)
bool cpu_work_list_empty(CPUState *cpu) bool cpu_work_list_empty(CPUState *cpu)
{ {
bool ret; return QSIMPLEQ_EMPTY_ATOMIC(&cpu->work_list);
qemu_mutex_lock(&cpu->work_mutex);
ret = QSIMPLEQ_EMPTY(&cpu->work_list);
qemu_mutex_unlock(&cpu->work_mutex);
return ret;
} }
bool cpu_thread_is_idle(CPUState *cpu) bool cpu_thread_is_idle(CPUState *cpu)