On 10/03/2017 16:14, Yang Zhong wrote:
> There are a lot of memory allocation during the qemu bootup, which are
> freed later by RCU thread,which means the heap size becomes biger and
> biger when allocation happens, but the heap may not be shrinked even
> after release happens,because some memory blocks in top of heap are still
> being used.Decreasing the sleep and removing qemu_mutex_unlock_iothread()
> lock, which make call_rcu_thread()thread response the free memory in time.
> This patch will reduce heap Rss around 10M.
>
> This patch is from Anthony xu <anthony...@intel.com>.
>
> Signed-off-by: Yang Zhong <yang.zh...@intel.com>
> ---
> util/rcu.c | 8 ++------
> 1 file changed, 2 insertions(+), 6 deletions(-)
>
> diff --git a/util/rcu.c b/util/rcu.c
> index 9adc5e4..c5c373c 100644
> --- a/util/rcu.c
> +++ b/util/rcu.c
> @@ -167,7 +167,7 @@ void synchronize_rcu(void)
> }
>
>
> -#define RCU_CALL_MIN_SIZE 30
> +#define RCU_CALL_MIN_SIZE 5
>
> /* Multi-producer, single-consumer queue based on urcu/static/wfqueue.h
> * from liburcu. Note that head is only used by the consumer.
> @@ -241,7 +241,7 @@ static void *call_rcu_thread(void *opaque)
> * added before synchronize_rcu() starts.
> */
> while (n == 0 || (n < RCU_CALL_MIN_SIZE && ++tries <= 5)) {
> - g_usleep(10000);
> + g_usleep(100);
> if (n == 0) {
> qemu_event_reset(&rcu_call_ready_event);
> n = atomic_read(&rcu_call_count);
> @@ -254,24 +254,20 @@ static void *call_rcu_thread(void *opaque)
>
> atomic_sub(&rcu_call_count, n);
> synchronize_rcu();
> - qemu_mutex_lock_iothread();
> while (n > 0) {
> node = try_dequeue();
> while (!node) {
> - qemu_mutex_unlock_iothread();
> qemu_event_reset(&rcu_call_ready_event);
> node = try_dequeue();
> if (!node) {
> qemu_event_wait(&rcu_call_ready_event);
> node = try_dequeue();
> }
> - qemu_mutex_lock_iothread();
> }
>
> n--;
> node->func(node);
> }
> - qemu_mutex_unlock_iothread();
This is wrong. RCU callbacks currently need the "big QEMU lock",
because they can free arbitrary QOM objects (including MemoryRegions).
Paolo
> }
> abort();
> }
>
