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Re: [Qemu-devel] [RFC PATCH 3/3] qemu-coroutine: use a ring per thread f
From: |
Peter Lieven |
Subject: |
Re: [Qemu-devel] [RFC PATCH 3/3] qemu-coroutine: use a ring per thread for the pool |
Date: |
Fri, 28 Nov 2014 13:39:17 +0100 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.2.0 |
Am 28.11.2014 um 13:26 schrieb Paolo Bonzini:
>
> On 28/11/2014 12:46, Peter Lieven wrote:
>>> I get:
>>> Run operation 40000000 iterations 9.883958 s, 4046K operations/s, 247ns per
>>> coroutine
>> Ok, understood, it "steals" the whole pool, right? Isn't that bad if we have
>> more
>> than one thread in need of a lot of coroutines?
> Overall the algorithm is expected to adapt. The N threads contribute to
> the global release pool, so the pool will fill up N times faster than if
> you had only one thread. There can be some variance, which is why the
> maximum size of the pool is twice the threshold (and probably could be
> tuned better).
>
> Benchmarks are needed on real I/O too, of course, especially with high
> queue depth.
Yes, cool. The atomic operations are a bit tricky at the first glance ;-)
Question:
Why is the pool_size increment atomic and the set to zero not?
Idea:
If the release_pool is full why not put the coroutine in the thread alloc_pool
instead of throwing it away? :-)
Run operation 40000000 iterations 9.057805 s, 4416K operations/s, 226ns per
coroutine
diff --git a/qemu-coroutine.c b/qemu-coroutine.c
index 6bee354..edea162 100644
--- a/qemu-coroutine.c
+++ b/qemu-coroutine.c
@@ -25,8 +25,9 @@ enum {
/** Free list to speed up creation */
static QSLIST_HEAD(, Coroutine) release_pool = QSLIST_HEAD_INITIALIZER(pool);
-static unsigned int pool_size;
+static unsigned int release_pool_size;
static __thread QSLIST_HEAD(, Coroutine) alloc_pool =
QSLIST_HEAD_INITIALIZER(pool);
+static __thread unsigned int alloc_pool_size;
/* The GPrivate is only used to invoke coroutine_pool_cleanup. */
static void coroutine_pool_cleanup(void *value);
@@ -39,12 +40,12 @@ Coroutine *qemu_coroutine_create(CoroutineEntry *entry)
if (CONFIG_COROUTINE_POOL) {
co = QSLIST_FIRST(&alloc_pool);
if (!co) {
- if (pool_size > POOL_BATCH_SIZE) {
- /* This is not exact; there could be a little skew between
pool_size
+ if (release_pool_size > POOL_BATCH_SIZE) {
+ /* This is not exact; there could be a little skew between
release_pool_size
* and the actual size of alloc_pool. But it is just a
heuristic,
* it does not need to be perfect.
*/
- pool_size = 0;
+ alloc_pool_size = atomic_fetch_and(&release_pool_size, 0);
QSLIST_MOVE_ATOMIC(&alloc_pool, &release_pool);
co = QSLIST_FIRST(&alloc_pool);
@@ -53,6 +54,8 @@ Coroutine *qemu_coroutine_create(CoroutineEntry *entry)
*/
g_private_set(&dummy_key, &dummy_key);
}
+ } else {
+ alloc_pool_size--;
}
if (co) {
QSLIST_REMOVE_HEAD(&alloc_pool, pool_next);
@@ -71,10 +74,15 @@ Coroutine *qemu_coroutine_create(CoroutineEntry *entry)
static void coroutine_delete(Coroutine *co)
{
if (CONFIG_COROUTINE_POOL) {
- if (pool_size < POOL_BATCH_SIZE * 2) {
+ if (release_pool_size < POOL_BATCH_SIZE * 2) {
co->caller = NULL;
QSLIST_INSERT_HEAD_ATOMIC(&release_pool, co, pool_next);
- atomic_inc(&pool_size);
+ atomic_inc(&release_pool_size);
+ return;
+ } else if (alloc_pool_size < POOL_BATCH_SIZE) {
+ co->caller = NULL;
+ QSLIST_INSERT_HEAD(&alloc_pool, co, pool_next);
+ alloc_pool_size++;
return;
}
}
Bug?:
The release_pool is not cleanup up on termination I think.
Peter
- Re: [Qemu-devel] [RFC PATCH 3/3] qemu-coroutine: use a ring per thread for the pool, (continued)
- Re: [Qemu-devel] [RFC PATCH 3/3] qemu-coroutine: use a ring per thread for the pool, Paolo Bonzini, 2014/11/27
- Re: [Qemu-devel] [RFC PATCH 3/3] qemu-coroutine: use a ring per thread for the pool, Peter Lieven, 2014/11/28
- Message not available
- Re: [Qemu-devel] [RFC PATCH 3/3] qemu-coroutine: use a ring per thread for the pool, Peter Lieven, 2014/11/28
- Re: [Qemu-devel] [RFC PATCH 3/3] qemu-coroutine: use a ring per thread for the pool, Paolo Bonzini, 2014/11/28
- Re: [Qemu-devel] [RFC PATCH 3/3] qemu-coroutine: use a ring per thread for the pool, Peter Lieven, 2014/11/28
- Re: [Qemu-devel] [RFC PATCH 3/3] qemu-coroutine: use a ring per thread for the pool, Paolo Bonzini, 2014/11/28
- Re: [Qemu-devel] [RFC PATCH 3/3] qemu-coroutine: use a ring per thread for the pool, Peter Lieven, 2014/11/28
- Re: [Qemu-devel] [RFC PATCH 3/3] qemu-coroutine: use a ring per thread for the pool, Peter Lieven, 2014/11/28
- Re: [Qemu-devel] [RFC PATCH 3/3] qemu-coroutine: use a ring per thread for the pool, Peter Lieven, 2014/11/28
- Re: [Qemu-devel] [RFC PATCH 3/3] qemu-coroutine: use a ring per thread for the pool, Paolo Bonzini, 2014/11/28
- Re: [Qemu-devel] [RFC PATCH 3/3] qemu-coroutine: use a ring per thread for the pool,
Peter Lieven <=
- Re: [Qemu-devel] [RFC PATCH 3/3] qemu-coroutine: use a ring per thread for the pool, Paolo Bonzini, 2014/11/28
- Re: [Qemu-devel] [RFC PATCH 3/3] qemu-coroutine: use a ring per thread for the pool, Peter Lieven, 2014/11/28
- Re: [Qemu-devel] [RFC PATCH 3/3] qemu-coroutine: use a ring per thread for the pool, Paolo Bonzini, 2014/11/28
- Re: [Qemu-devel] [RFC PATCH 3/3] qemu-coroutine: use a ring per thread for the pool, Peter Lieven, 2014/11/28
- Re: [Qemu-devel] [RFC PATCH 3/3] qemu-coroutine: use a ring per thread for the pool, Paolo Bonzini, 2014/11/28
- Re: [Qemu-devel] [RFC PATCH 3/3] qemu-coroutine: use a ring per thread for the pool, Peter Lieven, 2014/11/28
- Re: [Qemu-devel] [RFC PATCH 3/3] qemu-coroutine: use a ring per thread for the pool, Peter Lieven, 2014/11/28
- Re: [Qemu-devel] [RFC PATCH 3/3] qemu-coroutine: use a ring per thread for the pool, Paolo Bonzini, 2014/11/28
- Re: [Qemu-devel] [RFC PATCH 3/3] qemu-coroutine: use a ring per thread for the pool, Peter Lieven, 2014/11/28
Re: [Qemu-devel] [RFC PATCH 3/3] qemu-coroutine: use a ring per thread for the pool, Stefan Hajnoczi, 2014/11/28