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Enable tuning of qemu network tap device "sndbuf" size

Browse Source 
This is in response to a request in:

   https://bugzilla.redhat.com/show_bug.cgi?id=665293

In short, under heavy load, it's possible for qemu's networking to
lock up due to the tap device's default 1MB sndbuf being
inadequate. adding "sndbuf=0" to the qemu commandline -netdevice
option will alleviate this problem (sndbuf=0 actually sets it to
0xffffffff).

Because we must be able to explicitly specify "0" as a value, the
standard practice of "0 means not specified" won't work here. Instead,
virDomainNetDef also has a sndbuf_specified, which defaults to 0, but
is set to 1 if some value was given.

The sndbuf value is put inside a <tune> element of each <interface> in
the domain. The intent is that further tunable settings will also be
placed inside this element.

     <interface type='network'>
       ...
       <tune>
         <sndbuf>0</sndbuf>
       ...
       </tune>
     </interface>
This commit is contained in:
Laine Stump 2011-01-12 14:38:01 -05:00
parent 175077fd70
commit fe053dbea7
4 changed files with 64 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

10
docs/schemas/domain.rng
View File

@ -1025,6 +1025,16 @@
<ref name="filterref-node-attributes"/>
</element>
</optional>
<optional>
<element name="tune">
<optional>
<!-- size of send buffer for network tap devices -->
<element name="sndbuf">
<ref name="unsignedInt"/>
</element>
</optional>
</element>
</optional>
</interleave>
</define>
<define name="virtualPortProfile">

35
src/conf/domain_conf.c
View File

@ -2296,6 +2296,7 @@ err_exit:
static virDomainNetDefPtr
virDomainNetDefParseXML(virCapsPtr caps,
xmlNodePtr node,
xmlXPathContextPtr ctxt,
int flags ATTRIBUTE_UNUSED) {
virDomainNetDefPtr def;
xmlNodePtr cur;
@ -2317,12 +2318,16 @@ virDomainNetDefParseXML(virCapsPtr caps,
virNWFilterHashTablePtr filterparams = NULL;
virVirtualPortProfileParams virtPort;
bool virtPortParsed = false;
xmlNodePtr oldnode = ctxt->node;
int ret;
if (VIR_ALLOC(def) < 0) {
virReportOOMError();
return NULL;
}
ctxt->node = node;
type = virXMLPropString(node, "type");
if (type != NULL) {
if ((int)(def->type = virDomainNetTypeFromString(type)) < 0) {
@ -2610,7 +2615,17 @@ virDomainNetDefParseXML(virCapsPtr caps,
}
}
ret = virXPathULong("string(./tune/sndbuf)", ctxt, &def->tune.sndbuf);
if (ret >= 0) {
def->tune.sndbuf_specified = true;
} else if (ret == -2) {
virDomainReportError(VIR_ERR_XML_ERROR, "%s",
_("sndbuf must be a positive integer"));
goto error;
}
cleanup:
ctxt->node = oldnode;
VIR_FREE(macaddr);
VIR_FREE(network);
VIR_FREE(address);
@ -4348,6 +4363,7 @@ virDomainDeviceDefPtr virDomainDeviceDefParse(virCapsPtr caps,
{
xmlDocPtr xml;
xmlNodePtr node;
xmlXPathContextPtr ctxt = NULL;
virDomainDeviceDefPtr dev = NULL;
if (!(xml = xmlReadDoc(BAD_CAST xmlStr, "device.xml", NULL,
@ -4364,6 +4380,13 @@ virDomainDeviceDefPtr virDomainDeviceDefParse(virCapsPtr caps,
goto error;
}
ctxt = xmlXPathNewContext(xml);
if (ctxt == NULL) {
virReportOOMError();
goto error;
}
ctxt->node = node;
if (VIR_ALLOC(dev) < 0) {
virReportOOMError();
goto error;
@ -4379,7 +4402,7 @@ virDomainDeviceDefPtr virDomainDeviceDefParse(virCapsPtr caps,
goto error;
} else if (xmlStrEqual(node->name, BAD_CAST "interface")) {
dev->type = VIR_DOMAIN_DEVICE_NET;
if (!(dev->data.net = virDomainNetDefParseXML(caps, node, flags)))
if (!(dev->data.net = virDomainNetDefParseXML(caps, node, ctxt, flags)))
goto error;
} else if (xmlStrEqual(node->name, BAD_CAST "input")) {
dev->type = VIR_DOMAIN_DEVICE_INPUT;
@ -4417,11 +4440,12 @@ virDomainDeviceDefPtr virDomainDeviceDefParse(virCapsPtr caps,
}
xmlFreeDoc(xml);
xmlXPathFreeContext(ctxt);
return dev;
error:
xmlFreeDoc(xml);
xmlXPathFreeContext(ctxt);
VIR_FREE(dev);
return NULL;
}
@ -5092,6 +5116,7 @@ static virDomainDefPtr virDomainDefParseXML(virCapsPtr caps,
for (i = 0 ; i < n ; i++) {
virDomainNetDefPtr net = virDomainNetDefParseXML(caps,
nodes[i],
ctxt,
flags);
if (!net)
goto error;
@ -6360,6 +6385,12 @@ virDomainNetDefFormat(virBufferPtr buf,
VIR_FREE(attrs);
}
if (def->tune.sndbuf_specified) {
virBufferAddLit(buf, " <tune>\n");
virBufferVSprintf(buf, " <sndbuf>%lu</sndbuf>\n", def->tune.sndbuf);
virBufferAddLit(buf, " </tune>\n");
}
if (virDomainDeviceInfoFormat(buf, &def->info, flags) < 0)
return -1;

4
src/conf/domain_conf.h
View File

@ -346,6 +346,10 @@ struct _virDomainNetDef {
virVirtualPortProfileParams virtPortProfile;
} direct;
} data;
struct {
bool sndbuf_specified;
unsigned long sndbuf;
} tune;
char *ifname;
virDomainDeviceInfo info;
char *filter;

19
src/qemu/qemu_command.c
View File

@ -1584,6 +1584,7 @@ qemuBuildHostNetStr(virDomainNetDefPtr net,
const char *tapfd,
const char *vhostfd)
{
bool is_tap = false;
virBuffer buf = VIR_BUFFER_INITIALIZER;
switch (net->type) {
@ -1593,6 +1594,7 @@ qemuBuildHostNetStr(virDomainNetDefPtr net,
virBufferAddLit(&buf, "tap");
virBufferVSprintf(&buf, "%cfd=%s", type_sep, tapfd);
type_sep = ',';
is_tap = true;
break;
case VIR_DOMAIN_NET_TYPE_ETHERNET:
@ -1606,6 +1608,7 @@ qemuBuildHostNetStr(virDomainNetDefPtr net,
net->data.ethernet.script);
type_sep = ',';
}
is_tap = true;
break;
case VIR_DOMAIN_NET_TYPE_CLIENT:
@ -1659,8 +1662,11 @@ qemuBuildHostNetStr(virDomainNetDefPtr net,
type_sep, net->info.alias);
}
if (vhostfd && *vhostfd) {
virBufferVSprintf(&buf, ",vhost=on,vhostfd=%s", vhostfd);
if (is_tap) {
if (vhostfd && *vhostfd)
virBufferVSprintf(&buf, ",vhost=on,vhostfd=%s", vhostfd);
if (net->tune.sndbuf_specified)
virBufferVSprintf(&buf, ",sndbuf=%lu", net->tune.sndbuf);
}
if (virBufferError(&buf)) {
@ -4669,6 +4675,15 @@ qemuParseCommandLineNet(virCapsPtr caps,
} else if (STREQ(keywords[i], "off")) {
def->backend = VIR_DOMAIN_NET_BACKEND_TYPE_QEMU;
}
} else if (STREQ(keywords[i], "sndbuf") && values[i]) {
if (virStrToLong_ul(values[i], NULL, 10, &def->tune.sndbuf) < 0) {
qemuReportError(VIR_ERR_INTERNAL_ERROR,
_("cannot parse sndbuf size in '%s'"), val);
virDomainNetDefFree(def);
def = NULL;
goto cleanup;
}
def->tune.sndbuf_specified = true;
}
}