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[PATCH V2] virtiofsd: Use --thread-pool-size=0 to mean no thread pool

Vivek Goyal posted 1 patch 3 years, 5 months ago
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git fetch https://github.com/patchew-project/qemu tags/patchew/20201109143548.GA1479853@redhat.com
Maintainers: Stefan Hajnoczi <stefanha@redhat.com>, "Dr. David Alan Gilbert" <dgilbert@redhat.com>
There is a newer version of this series
tools/virtiofsd/fuse_virtio.c | 36 ++++++++++++++++++++++++++---------
1 file changed, 27 insertions(+), 9 deletions(-)
[PATCH V2] virtiofsd: Use --thread-pool-size=0 to mean no thread pool
Posted by Vivek Goyal 3 years, 5 months ago 
Right now we create a thread pool and main thread hands over the request
to thread in thread pool to process. Number of threads in thread pool
can be managed by option --thread-pool-size.

In tests we have noted that many of the workloads are getting better
performance if we don't use a thread pool at all and process all
the requests in the context of a thread receiving the request.

Hence give user an option to be able to run virtiofsd without using
a thread pool.

To implement this, I have used existing option --thread-pool-size. This
option defines how many maximum threads can be in the thread pool.
Thread pool size zero freezes thead pool. I can't see why will one
start virtiofsd with a frozen thread pool (hence frozen file system).
So I am redefining --thread-pool-size=0 to mean, don't use a thread pool.
Instead process the request in the context of thread receiving request
from the queue.

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
---
 tools/virtiofsd/fuse_virtio.c | 36 ++++++++++++++++++++++++++---------
 1 file changed, 27 insertions(+), 9 deletions(-)

diff --git a/tools/virtiofsd/fuse_virtio.c b/tools/virtiofsd/fuse_virtio.c
index 83ba07c6cd..944b9a577c 100644
--- a/tools/virtiofsd/fuse_virtio.c
+++ b/tools/virtiofsd/fuse_virtio.c
@@ -588,13 +588,18 @@ static void *fv_queue_thread(void *opaque)
     struct VuDev *dev = &qi->virtio_dev->dev;
     struct VuVirtq *q = vu_get_queue(dev, qi->qidx);
     struct fuse_session *se = qi->virtio_dev->se;
-    GThreadPool *pool;
-
-    pool = g_thread_pool_new(fv_queue_worker, qi, se->thread_pool_size, FALSE,
-                             NULL);
-    if (!pool) {
-        fuse_log(FUSE_LOG_ERR, "%s: g_thread_pool_new failed\n", __func__);
-        return NULL;
+    GThreadPool *pool = NULL;
+    GList *req_list = NULL;
+
+    if (se->thread_pool_size) {
+        fuse_log(FUSE_LOG_DEBUG, "%s: Creating thread pool for Queue %d\n",
+                 __func__, qi->qidx);
+        pool = g_thread_pool_new(fv_queue_worker, qi, se->thread_pool_size,
+                                 FALSE, NULL);
+        if (!pool) {
+            fuse_log(FUSE_LOG_ERR, "%s: g_thread_pool_new failed\n", __func__);
+            return NULL;
+        }
     }
 
     fuse_log(FUSE_LOG_INFO, "%s: Start for queue %d kick_fd %d\n", __func__,
@@ -669,14 +674,27 @@ static void *fv_queue_thread(void *opaque)
 
             req->reply_sent = false;
 
-            g_thread_pool_push(pool, req, NULL);
+            if (!se->thread_pool_size) {
+                req_list = g_list_prepend(req_list, req);
+            } else {
+                g_thread_pool_push(pool, req, NULL);
+            }
         }
 
         pthread_mutex_unlock(&qi->vq_lock);
         pthread_rwlock_unlock(&qi->virtio_dev->vu_dispatch_rwlock);
+
+        /* Process all the requests. */
+        if (!se->thread_pool_size && req_list != NULL) {
+            g_list_foreach(req_list, fv_queue_worker, qi);
+            g_list_free(req_list);
+            req_list = NULL;
+        }
     }
 
-    g_thread_pool_free(pool, FALSE, TRUE);
+    if (pool) {
+        g_thread_pool_free(pool, FALSE, TRUE);
+    }
 
     return NULL;
 }
-- 
2.25.4
Re: [PATCH V2] virtiofsd: Use --thread-pool-size=0 to mean no thread pool
Posted by Stefan Hajnoczi 3 years, 5 months ago 
On Mon, Nov 09, 2020 at 09:35:48AM -0500, Vivek Goyal wrote:
> Right now we create a thread pool and main thread hands over the request
> to thread in thread pool to process. Number of threads in thread pool
> can be managed by option --thread-pool-size.
> 
> In tests we have noted that many of the workloads are getting better
> performance if we don't use a thread pool at all and process all
> the requests in the context of a thread receiving the request.
> 
> Hence give user an option to be able to run virtiofsd without using
> a thread pool.
> 
> To implement this, I have used existing option --thread-pool-size. This
> option defines how many maximum threads can be in the thread pool.
> Thread pool size zero freezes thead pool. I can't see why will one
> start virtiofsd with a frozen thread pool (hence frozen file system).
> So I am redefining --thread-pool-size=0 to mean, don't use a thread pool.
> Instead process the request in the context of thread receiving request
> from the queue.
> 
> Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
> ---
>  tools/virtiofsd/fuse_virtio.c | 36 ++++++++++++++++++++++++++---------
>  1 file changed, 27 insertions(+), 9 deletions(-)

This is useful for benchmarking. For production we need to understand
the cause of the performance difference so that virtiofsd can adapt to
the workload without setting a specific thread-pool-size value.

Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Re: [PATCH V2] virtiofsd: Use --thread-pool-size=0 to mean no thread pool
Posted by Dr. David Alan Gilbert 3 years, 4 months ago 
* Vivek Goyal (vgoyal@redhat.com) wrote:
> Right now we create a thread pool and main thread hands over the request
> to thread in thread pool to process. Number of threads in thread pool
> can be managed by option --thread-pool-size.
> 
> In tests we have noted that many of the workloads are getting better
> performance if we don't use a thread pool at all and process all
> the requests in the context of a thread receiving the request.
> 
> Hence give user an option to be able to run virtiofsd without using
> a thread pool.
> 
> To implement this, I have used existing option --thread-pool-size. This
> option defines how many maximum threads can be in the thread pool.
> Thread pool size zero freezes thead pool. I can't see why will one
> start virtiofsd with a frozen thread pool (hence frozen file system).
> So I am redefining --thread-pool-size=0 to mean, don't use a thread pool.
> Instead process the request in the context of thread receiving request
> from the queue.
> 
> Signed-off-by: Vivek Goyal <vgoyal@redhat.com>

Queued.

> ---
>  tools/virtiofsd/fuse_virtio.c | 36 ++++++++++++++++++++++++++---------
>  1 file changed, 27 insertions(+), 9 deletions(-)
> 
> diff --git a/tools/virtiofsd/fuse_virtio.c b/tools/virtiofsd/fuse_virtio.c
> index 83ba07c6cd..944b9a577c 100644
> --- a/tools/virtiofsd/fuse_virtio.c
> +++ b/tools/virtiofsd/fuse_virtio.c
> @@ -588,13 +588,18 @@ static void *fv_queue_thread(void *opaque)
>      struct VuDev *dev = &qi->virtio_dev->dev;
>      struct VuVirtq *q = vu_get_queue(dev, qi->qidx);
>      struct fuse_session *se = qi->virtio_dev->se;
> -    GThreadPool *pool;
> -
> -    pool = g_thread_pool_new(fv_queue_worker, qi, se->thread_pool_size, FALSE,
> -                             NULL);
> -    if (!pool) {
> -        fuse_log(FUSE_LOG_ERR, "%s: g_thread_pool_new failed\n", __func__);
> -        return NULL;
> +    GThreadPool *pool = NULL;
> +    GList *req_list = NULL;
> +
> +    if (se->thread_pool_size) {
> +        fuse_log(FUSE_LOG_DEBUG, "%s: Creating thread pool for Queue %d\n",
> +                 __func__, qi->qidx);
> +        pool = g_thread_pool_new(fv_queue_worker, qi, se->thread_pool_size,
> +                                 FALSE, NULL);
> +        if (!pool) {
> +            fuse_log(FUSE_LOG_ERR, "%s: g_thread_pool_new failed\n", __func__);
> +            return NULL;
> +        }
>      }
>  
>      fuse_log(FUSE_LOG_INFO, "%s: Start for queue %d kick_fd %d\n", __func__,
> @@ -669,14 +674,27 @@ static void *fv_queue_thread(void *opaque)
>  
>              req->reply_sent = false;
>  
> -            g_thread_pool_push(pool, req, NULL);
> +            if (!se->thread_pool_size) {
> +                req_list = g_list_prepend(req_list, req);
> +            } else {
> +                g_thread_pool_push(pool, req, NULL);
> +            }
>          }
>  
>          pthread_mutex_unlock(&qi->vq_lock);
>          pthread_rwlock_unlock(&qi->virtio_dev->vu_dispatch_rwlock);
> +
> +        /* Process all the requests. */
> +        if (!se->thread_pool_size && req_list != NULL) {
> +            g_list_foreach(req_list, fv_queue_worker, qi);
> +            g_list_free(req_list);
> +            req_list = NULL;
> +        }
>      }
>  
> -    g_thread_pool_free(pool, FALSE, TRUE);
> +    if (pool) {
> +        g_thread_pool_free(pool, FALSE, TRUE);
> +    }
>  
>      return NULL;
>  }
> -- 
> 2.25.4
> 
> 
-- 
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK
Re: [PATCH V2] virtiofsd: Use --thread-pool-size=0 to mean no thread pool
Posted by Dr. David Alan Gilbert 3 years, 5 months ago 
* Vivek Goyal (vgoyal@redhat.com) wrote:
> Right now we create a thread pool and main thread hands over the request
> to thread in thread pool to process. Number of threads in thread pool
> can be managed by option --thread-pool-size.
> 
> In tests we have noted that many of the workloads are getting better
> performance if we don't use a thread pool at all and process all
> the requests in the context of a thread receiving the request.
> 
> Hence give user an option to be able to run virtiofsd without using
> a thread pool.
> 
> To implement this, I have used existing option --thread-pool-size. This
> option defines how many maximum threads can be in the thread pool.
> Thread pool size zero freezes thead pool. I can't see why will one
> start virtiofsd with a frozen thread pool (hence frozen file system).
> So I am redefining --thread-pool-size=0 to mean, don't use a thread pool.
> Instead process the request in the context of thread receiving request
> from the queue.
> 
> Signed-off-by: Vivek Goyal <vgoyal@redhat.com>

Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

> ---
>  tools/virtiofsd/fuse_virtio.c | 36 ++++++++++++++++++++++++++---------
>  1 file changed, 27 insertions(+), 9 deletions(-)
> 
> diff --git a/tools/virtiofsd/fuse_virtio.c b/tools/virtiofsd/fuse_virtio.c
> index 83ba07c6cd..944b9a577c 100644
> --- a/tools/virtiofsd/fuse_virtio.c
> +++ b/tools/virtiofsd/fuse_virtio.c
> @@ -588,13 +588,18 @@ static void *fv_queue_thread(void *opaque)
>      struct VuDev *dev = &qi->virtio_dev->dev;
>      struct VuVirtq *q = vu_get_queue(dev, qi->qidx);
>      struct fuse_session *se = qi->virtio_dev->se;
> -    GThreadPool *pool;
> -
> -    pool = g_thread_pool_new(fv_queue_worker, qi, se->thread_pool_size, FALSE,
> -                             NULL);
> -    if (!pool) {
> -        fuse_log(FUSE_LOG_ERR, "%s: g_thread_pool_new failed\n", __func__);
> -        return NULL;
> +    GThreadPool *pool = NULL;
> +    GList *req_list = NULL;
> +
> +    if (se->thread_pool_size) {
> +        fuse_log(FUSE_LOG_DEBUG, "%s: Creating thread pool for Queue %d\n",
> +                 __func__, qi->qidx);
> +        pool = g_thread_pool_new(fv_queue_worker, qi, se->thread_pool_size,
> +                                 FALSE, NULL);
> +        if (!pool) {
> +            fuse_log(FUSE_LOG_ERR, "%s: g_thread_pool_new failed\n", __func__);
> +            return NULL;
> +        }
>      }
>  
>      fuse_log(FUSE_LOG_INFO, "%s: Start for queue %d kick_fd %d\n", __func__,
> @@ -669,14 +674,27 @@ static void *fv_queue_thread(void *opaque)
>  
>              req->reply_sent = false;
>  
> -            g_thread_pool_push(pool, req, NULL);
> +            if (!se->thread_pool_size) {
> +                req_list = g_list_prepend(req_list, req);
> +            } else {
> +                g_thread_pool_push(pool, req, NULL);
> +            }
>          }
>  
>          pthread_mutex_unlock(&qi->vq_lock);
>          pthread_rwlock_unlock(&qi->virtio_dev->vu_dispatch_rwlock);
> +
> +        /* Process all the requests. */
> +        if (!se->thread_pool_size && req_list != NULL) {
> +            g_list_foreach(req_list, fv_queue_worker, qi);
> +            g_list_free(req_list);
> +            req_list = NULL;
> +        }
>      }
>  
> -    g_thread_pool_free(pool, FALSE, TRUE);
> +    if (pool) {
> +        g_thread_pool_free(pool, FALSE, TRUE);
> +    }
>  
>      return NULL;
>  }
> -- 
> 2.25.4
> 
-- 
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK

Patchew 2.1-devel-0870f84

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