krbd: increase udev netlink socket receive buffer to 2M

Even though with the previous commit we no longer block between binding
the socket and starting handling events, we still want a larger receive
buffer to accommodate for scheduling delays.  Since the filtering is
done in the listener, an estimate focused on just rbd is not accurate,
but anyway: a pair of "rbd" and "block" events for "rbd map" take 2048
bytes in the receive buffer.  This allows for roughly a thousand of
them ("rbd map" and "rbd unmap" require root and libudev makes use of
SO_RCVBUFFORCE so rmem_max limit is ignored).

Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
(cherry picked from commit 1c6cac1acaefdf59c3265d70c8d2191c59f14652)

Conflicts:
	src/krbd.cc [ trivial context ]

diff --git a/src/krbd.cc b/src/krbd.cc
index 588185129ff4b3c11211ca3fe756b7be1f25c914..c35f15ac45411a15685919f1ef3e1af238312ba3 100644 (file)
--- a/src/krbd.cc
+++ b/src/krbd.cc
@@ -46,6 +46,8 @@
 
 using namespace std;
 
+static const int UDEV_BUF_SIZE = 1 << 20;  /* doubled to 2M (SO_RCVBUFFORCE) */
+
 struct krbd_ctx {
   CephContext *cct;
   struct udev *udev;
@@ -344,6 +346,13 @@ static int do_map(struct udev *udev, const char *pool, const char *image,
   if (r < 0)
     goto out_mon;
 
+  r = udev_monitor_set_receive_buffer_size(mon, UDEV_BUF_SIZE);
+  if (r < 0) {
+    std::cerr << "rbd: failed to set udev buffer size: " << cpp_strerror(r)
+              << std::endl;
+    /* not fatal */
+  }
+
   r = udev_monitor_enable_receiving(mon);
   if (r < 0)
     goto out_mon;
@@ -600,6 +609,13 @@ static int do_unmap(struct udev *udev, dev_t devno, const string& buf)
   if (r < 0)
     goto out_mon;
 
+  r = udev_monitor_set_receive_buffer_size(mon, UDEV_BUF_SIZE);
+  if (r < 0) {
+    std::cerr << "rbd: failed to set udev buffer size: " << cpp_strerror(r)
+              << std::endl;
+    /* not fatal */
+  }
+
   r = udev_monitor_enable_receiving(mon);
   if (r < 0)
     goto out_mon;