haraldwolff/qemu-patch-raspberry4
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rcutorture: remove synchronize_rcu from readers

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This gives much worse numbers for readers, especially if synchronize_rcu
is made more expensive as is the case with --enable-membarrier.  Before:

   $ tests/rcutorture 10 stress 10
   n_reads: 98304  n_updates: 529  n_mberror: 0
   rcu_stress_count: 98302 2 0 0 0 0 0 0 0 0 0

After:

   $ tests/rcutorture 10 stress 10
   n_reads: 165158482  n_updates: 429  n_mberror: 0
   rcu_stress_count: 165154364 4118 0 0 0 0 0 0 0 0 0

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Paolo Bonzini 2018-03-09 12:12:29 +01:00
parent 148b2ba114
commit b9b7581754
1 changed files with 0 additions and 4 deletions
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4
tests/rcutorture.c
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@ -238,7 +238,6 @@ long long rcu_stress_count[RCU_STRESS_PIPE_LEN + 1];
static void *rcu_read_stress_test(void *arg)
{
int i;
int itercnt = 0;
struct rcu_stress *p;
int pc;
long long n_reads_local = 0;
@ -269,9 +268,6 @@ static void *rcu_read_stress_test(void *arg)
}
rcu_stress_local[pc]++;
n_reads_local++;
if ((++itercnt % 0x1000) == 0) {
synchronize_rcu();
}
}
qemu_mutex_lock(&counts_mutex);
n_reads += n_reads_local;