hv_vmbus: Add gradually increased delay for retries in vmbus_post_msg()

Most of the retries can be done within a millisecond successfully, so we
sleep 1ms before the first retry, then gradually increase the retry
interval to 2^n with max value of 2048ms. Doing so, we will have shorter
overall delay time, because most of the cases succeed within 1-2 attempts.

Signed-off-by: Haiyang Zhang <haiyangz@microsoft.com>
Reviewed-by: K. Y. Srinivasan <kys@microsoft.com>
Reviewed-by: Dexuan Cui <decui@microsoft.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/hv/connection.c b/drivers/hv/connection.c
index 583d7d42b46d84916615f3e7de2c17e28a0ce813..b27220a425f4a44b6b1143f39017998f1b77533a 100644 (file)
--- a/drivers/hv/connection.c
+++ b/drivers/hv/connection.c
@@ -422,6 +422,7 @@ int vmbus_post_msg(void *buffer, size_t buflen)
        union hv_connection_id conn_id;
        int ret = 0;
        int retries = 0;
+       u32 msec = 1;
 
        conn_id.asu32 = 0;
        conn_id.u.id = VMBUS_MESSAGE_CONNECTION_ID;
@@ -431,7 +432,7 @@ int vmbus_post_msg(void *buffer, size_t buflen)
         * insufficient resources. Retry the operation a couple of
         * times before giving up.
         */
-       while (retries < 10) {
+       while (retries < 20) {
                ret = hv_post_message(conn_id, 1, buffer, buflen);
 
                switch (ret) {
@@ -454,7 +455,9 @@ int vmbus_post_msg(void *buffer, size_t buflen)
                }
 
                retries++;
-               msleep(1000);
+               msleep(msec);
+               if (msec < 2048)
+                       msec *= 2;
        }
        return ret;
 }