Alex Bennée <[email protected]> writes:
> Under times of high memory stress the additional small mallocs by a
> linked list are source of potential memory fragmentation. As we have
> worked hard to avoid mallocs elsewhere when queuing work we might as
> well do the same for the list. We convert the lists to a auto-resizeing
> GArray which will re-size in steps of powers of 2.
<snip>
> diff --git a/cpu-exec-common.c b/cpu-exec-common.c
> index 6d5da15..745d973 100644
> --- a/cpu-exec-common.c
> +++ b/cpu-exec-common.c
> @@ -113,17 +113,18 @@ void wait_safe_cpu_work(void)
> static void queue_work_on_cpu(CPUState *cpu, struct qemu_work_item *wi)
> {
> qemu_mutex_lock(&cpu->work_mutex);
> - if (cpu->queued_work_first == NULL) {
> - cpu->queued_work_first = wi;
> - } else {
> - cpu->queued_work_last->next = wi;
> +
> + if (!cpu->queued_work) {
> + cpu->queued_work = g_array_sized_new(true, true,
> + sizeof(struct qemu_work_item), 16);
> }
> - cpu->queued_work_last = wi;
> - wi->next = NULL;
> - wi->done = false;
> + trace_queue_work_on_cpu(cpu->cpu_index, wi->safe,
> cpu->queued_work->len);
Oops, this was left over from testing, I've posted an updated version of
the patch.
> +
> + g_array_append_val(cpu->queued_work, *wi);
> if (wi->safe) {
> atomic_inc(&safe_work_pending);
> }
> +
> qemu_mutex_unlock(&cpu->work_mutex);
>
> if (!wi->safe) {
> @@ -138,6 +139,7 @@ static void queue_work_on_cpu(CPUState *cpu, struct
> qemu_work_item *wi)
> void run_on_cpu(CPUState *cpu, run_on_cpu_func func, void *data)
> {
> struct qemu_work_item wi;
> + bool done = false;
>
> if (qemu_cpu_is_self(cpu)) {
> func(cpu, data);
> @@ -146,11 +148,11 @@ void run_on_cpu(CPUState *cpu, run_on_cpu_func func,
> void *data)
>
> wi.func = func;
> wi.data = data;
> - wi.free = false;
> wi.safe = false;
> + wi.done = &done;
>
> queue_work_on_cpu(cpu, &wi);
> - while (!atomic_mb_read(&wi.done)) {
> + while (!atomic_mb_read(&done)) {
> CPUState *self_cpu = current_cpu;
>
> qemu_cond_wait(&qemu_work_cond, qemu_get_cpu_work_mutex());
> @@ -160,70 +162,75 @@ void run_on_cpu(CPUState *cpu, run_on_cpu_func func,
> void *data)
>
> void async_run_on_cpu(CPUState *cpu, run_on_cpu_func func, void *data)
> {
> - struct qemu_work_item *wi;
> + struct qemu_work_item wi;
>
> if (qemu_cpu_is_self(cpu)) {
> func(cpu, data);
> return;
> }
>
> - wi = g_malloc0(sizeof(struct qemu_work_item));
> - wi->func = func;
> - wi->data = data;
> - wi->free = true;
> - wi->safe = false;
> + wi.func = func;
> + wi.data = data;
> + wi.safe = false;
> + wi.done = NULL;
>
> - queue_work_on_cpu(cpu, wi);
> + queue_work_on_cpu(cpu, &wi);
> }
>
> void async_safe_run_on_cpu(CPUState *cpu, run_on_cpu_func func, void *data)
> {
> - struct qemu_work_item *wi;
> + struct qemu_work_item wi;
>
> - wi = g_malloc0(sizeof(struct qemu_work_item));
> - wi->func = func;
> - wi->data = data;
> - wi->free = true;
> - wi->safe = true;
> + wi.func = func;
> + wi.data = data;
> + wi.safe = true;
> + wi.done = NULL;
>
> - queue_work_on_cpu(cpu, wi);
> + queue_work_on_cpu(cpu, &wi);
> }
>
> void process_queued_cpu_work(CPUState *cpu)
> {
> struct qemu_work_item *wi;
> -
> - if (cpu->queued_work_first == NULL) {
> - return;
> - }
> + GArray *work_list = NULL;
> + int i;
>
> qemu_mutex_lock(&cpu->work_mutex);
> - while (cpu->queued_work_first != NULL) {
> - wi = cpu->queued_work_first;
> - cpu->queued_work_first = wi->next;
> - if (!cpu->queued_work_first) {
> - cpu->queued_work_last = NULL;
> - }
> - if (wi->safe) {
> - while (tcg_pending_threads) {
> - qemu_cond_wait(&qemu_exclusive_cond,
> - qemu_get_cpu_work_mutex());
> +
> + work_list = cpu->queued_work;
> + cpu->queued_work = NULL;
> +
> + qemu_mutex_unlock(&cpu->work_mutex);
> +
> + if (work_list) {
> +
> + g_assert(work_list->len > 0);
> +
> + for (i = 0; i < work_list->len; i++) {
> + wi = &g_array_index(work_list, struct qemu_work_item, i);
> +
> + if (wi->safe) {
> + while (tcg_pending_threads) {
> + qemu_cond_wait(&qemu_exclusive_cond,
> + qemu_get_cpu_work_mutex());
> + }
> }
> - }
> - qemu_mutex_unlock(&cpu->work_mutex);
> - wi->func(cpu, wi->data);
> - qemu_mutex_lock(&cpu->work_mutex);
> - if (wi->safe) {
> - if (!atomic_dec_fetch(&safe_work_pending)) {
> - qemu_cond_broadcast(&qemu_safe_work_cond);
> +
> + wi->func(cpu, wi->data);
> +
> + if (wi->safe) {
> + if (!atomic_dec_fetch(&safe_work_pending)) {
> + qemu_cond_broadcast(&qemu_safe_work_cond);
> + }
> + }
> +
> + if (wi->done) {
> + atomic_mb_set(wi->done, true);
> }
> }
> - if (wi->free) {
> - g_free(wi);
> - } else {
> - atomic_mb_set(&wi->done, true);
> - }
> +
> + trace_process_queued_cpu_work(cpu->cpu_index,
> work_list->len);
And so was this.
--
Alex Bennée
