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[Qemu-devel] [PATCH 15/15] qemu-nbd: throttle requests
From: |
Paolo Bonzini |
Subject: |
[Qemu-devel] [PATCH 15/15] qemu-nbd: throttle requests |
Date: |
Mon, 10 Oct 2011 11:37:57 +0200 |
Limiting the number of in-flight requests is implemented very simply
with a can_read callback. It does not require a semaphore, unlike the
client side in block/nbd.c, because we can throttle directly the creation
of coroutines. The client side can have a coroutine created at any time
when an I/O request is made.
Signed-off-by: Paolo Bonzini <address@hidden>
---
nbd.c | 23 ++++++++++++++++++++---
1 files changed, 20 insertions(+), 3 deletions(-)
diff --git a/nbd.c b/nbd.c
index 01d3a85..1869212 100644
--- a/nbd.c
+++ b/nbd.c
@@ -589,6 +589,8 @@ static int nbd_send_reply(int csock, struct nbd_reply
*reply)
return 0;
}
+#define MAX_NBD_REQUESTS 16
+
typedef struct NBDRequest NBDRequest;
struct NBDRequest {
@@ -616,6 +618,8 @@ struct NBDClient {
CoMutex send_lock;
Coroutine *send_coroutine;
+
+ int nb_requests;
};
static void nbd_client_get(NBDClient *client)
@@ -646,6 +650,9 @@ static NBDRequest *nbd_request_get(NBDClient *client)
NBDRequest *req;
NBDExport *exp = client->exp;
+ assert(client->nb_requests < MAX_NBD_REQUESTS);
+ client->nb_requests++;
+
if (QSIMPLEQ_EMPTY(&exp->requests)) {
req = g_malloc0(sizeof(NBDRequest));
req->data = qemu_blockalign(exp->bs, NBD_BUFFER_SIZE);
@@ -662,6 +669,7 @@ static void nbd_request_put(NBDRequest *req)
{
NBDClient *client = req->client;
QSIMPLEQ_INSERT_HEAD(&client->exp->requests, req, entry);
+ client->nb_requests--;
nbd_client_put(client);
}
@@ -690,6 +698,7 @@ void nbd_export_close(NBDExport *exp)
g_free(exp);
}
+static int nbd_can_read(void *opaque);
static void nbd_read(void *opaque);
static void nbd_restart_write(void *opaque);
@@ -701,7 +710,8 @@ static int nbd_co_send_reply(NBDRequest *req, struct
nbd_reply *reply,
int rc, ret;
qemu_co_mutex_lock(&client->send_lock);
- qemu_set_fd_handler2(csock, NULL, nbd_read, nbd_restart_write, client);
+ qemu_set_fd_handler2(csock, nbd_can_read, nbd_read,
+ nbd_restart_write, client);
client->send_coroutine = qemu_coroutine_self();
if (!len) {
@@ -726,7 +736,7 @@ static int nbd_co_send_reply(NBDRequest *req, struct
nbd_reply *reply,
}
client->send_coroutine = NULL;
- qemu_set_fd_handler2(csock, NULL, nbd_read, NULL, client);
+ qemu_set_fd_handler2(csock, nbd_can_read, nbd_read, NULL, client);
qemu_co_mutex_unlock(&client->send_lock);
return rc;
}
@@ -902,6 +912,13 @@ out:
nbd_client_close(client);
}
+static int nbd_can_read(void *opaque)
+{
+ NBDClient *client = opaque;
+
+ return client->recv_coroutine || client->nb_requests < MAX_NBD_REQUESTS;
+}
+
static void nbd_read(void *opaque)
{
NBDClient *client = opaque;
@@ -933,6 +950,6 @@ NBDClient *nbd_client_new(NBDExport *exp, int csock,
client->sock = csock;
client->close = close;
qemu_co_mutex_init(&client->send_lock);
- qemu_set_fd_handler2(csock, NULL, nbd_read, NULL, client);
+ qemu_set_fd_handler2(csock, nbd_can_read, nbd_read, NULL, client);
return client;
}
--
1.7.6
- [Qemu-devel] [PATCH 06/15] qemu-nbd: more robust handling of invalid requests, (continued)
- [Qemu-devel] [PATCH 06/15] qemu-nbd: more robust handling of invalid requests, Paolo Bonzini, 2011/10/10
- [Qemu-devel] [PATCH 11/15] qemu-nbd: use common main loop, Paolo Bonzini, 2011/10/10
- [Qemu-devel] [PATCH 07/15] qemu-nbd: introduce nbd_do_receive_request, Paolo Bonzini, 2011/10/10
- [Qemu-devel] [PATCH 14/15] qemu-nbd: asynchronous operation, Paolo Bonzini, 2011/10/10
- [Qemu-devel] [PATCH 08/15] qemu-nbd: introduce NBDExport, Paolo Bonzini, 2011/10/10
- [Qemu-devel] [PATCH 05/15] qemu-nbd: introduce nbd_do_send_reply, Paolo Bonzini, 2011/10/10
- [Qemu-devel] [PATCH 12/15] qemu-nbd: move client handling to nbd.c, Paolo Bonzini, 2011/10/10
- [Qemu-devel] [PATCH 10/15] link the main loop and its dependencies into the tools, Paolo Bonzini, 2011/10/10
- [Qemu-devel] [PATCH 13/15] qemu-nbd: add client pointer to NBDRequest, Paolo Bonzini, 2011/10/10
- [Qemu-devel] [PATCH 09/15] qemu-nbd: introduce NBDRequest, Paolo Bonzini, 2011/10/10
- [Qemu-devel] [PATCH 15/15] qemu-nbd: throttle requests,
Paolo Bonzini <=
- Re: [Qemu-devel] [PATCH 00/15] NBD server improvements, Paolo Bonzini, 2011/10/11