[Xen-devel][PATCH] qemu xen-console, limit buffering

[Pat Campbell <plc@xxxxxxxxxx>]

Running this script from within a PV guest without having an xm console
attached can use all dom0 memory.
   
      while [ 1 ]; do ls -lR /usr > /dev/xvc0; done

Start of script:  (1% mem usage)
  PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND
10281 root           15   0 76536  14m 2448 S    2           1.0        
0:00.61  qemu-dm

Couple minutes later:  (17% mem usage)
   PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND
10281 root          16   0  291m 231m  2448 R    15        17.0     
0:16.34   qemu-dm
 
Much later:  (72.8% mem usage)
  PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND
10281 root         15    0 1052m 989m 2448 S    10        72.8     
1:13.25   qemu-dm

Attached patch sets dom->buffer.max_capacity to xend configured limit.

Please apply to xen-unstable tip.

Signed-off-by: Pat Campbell <plc@xxxxxxxxxx>


diff -r c33a40b4c22b tools/ioemu/hw/xen_console.c
--- a/tools/ioemu/hw/xen_console.c      Mon Jun 30 14:19:09 2008 +0100
+++ b/tools/ioemu/hw/xen_console.c      Mon Jun 30 17:06:22 2008 -0600
@@ -160,16 +160,18 @@ int xs_gather(struct xs_handle *xs, cons
 
 static int domain_create_ring(struct domain *dom)
 {
-       int err, remote_port, ring_ref, rc;
+       int err, remote_port, ring_ref, limit, rc;
 
        err = xs_gather(dom->xsh, dom->serialpath,
                        "ring-ref", "%u", &ring_ref,
                        "port", "%i", &remote_port,
+                       "limit", "%i", &limit,
                        NULL);
        if (err) {
                err = xs_gather(dom->xsh, dom->conspath,
                                "ring-ref", "%u", &ring_ref,
                                "port", "%i", &remote_port,
+                               "limit", "%i", &limit,
                                NULL);
                if (err) {
                        fprintf(stderr, "Console: failed to find ring-ref/port 
yet\n");
@@ -178,7 +180,9 @@ static int domain_create_ring(struct dom
                dom->use_consolepath = 1;
        } else
                dom->use_consolepath = 0;
-       fprintf(stderr, "Console: got ring-ref %d port %d\n", ring_ref, 
remote_port);
+       dom->buffer.max_capacity = limit;
+       fprintf(stderr, "Console: got ring-ref %d port %d limit %d\n", 
+               ring_ref, remote_port, limit);
 
        if ((ring_ref == dom->ring_ref) && (remote_port == dom->remote_port))
                goto out;

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