On 01/14/2011 08:27 AM, Daniel P. Berrange wrote:
On Thu, Jan 13, 2011 at 01:45:29AM -0500, Laine Stump wrote: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 elemnent. <interface type='network'> ... <tune> <sndbuf>0</sndbuf> ... </tune> </interface> --- Note that in qemuBuildHostNetStr() I have moved if (vhostfd&& *vhostfd) { virBufferVSprintf(&buf, ",vhost=on,vhostfd=%s", vhostfd); into a newly created "if (is_tap) { ... }" block. This always should have been inside such a conditional, but none existed until now. (I can make this a separate patch if anyone wants, but it seemed so simple and obvious that I took the slothenly way out :-) Also, as with the vhost patch, I didn't get the html docs updated for this addition either. I will add both in a single followup patch next week. docs/schemas/domain.rng | 10 ++++++++++ src/conf/domain_conf.c | 31 +++++++++++++++++++++++++++++-- src/conf/domain_conf.h | 4 ++++ src/qemu/qemu_command.c | 19 +++++++++++++++++-- 4 files changed, 60 insertions(+), 4 deletions(-) diff --git a/src/conf/domain_conf.c b/src/conf/domain_conf.c index 04ed502..5d1b8cf 100644 --- a/src/conf/domain_conf.c +++ b/src/conf/domain_conf.c @@ -2280,6 +2280,7 @@ err_exit: static virDomainNetDefPtr virDomainNetDefParseXML(virCapsPtr caps, xmlNodePtr node, + xmlXPathContextPtr ctxt, int flags ATTRIBUTE_UNUSED) { virDomainNetDefPtr def; xmlNodePtr cur; @@ -2298,15 +2299,19 @@ virDomainNetDefParseXML(virCapsPtr caps, char *internal = NULL; char *devaddr = NULL; char *mode = NULL; + unsigned long sndbuf; virNWFilterHashTablePtr filterparams = NULL; virVirtualPortProfileParams virtPort; bool virtPortParsed = false; + xmlNodePtr oldnode = ctxt->node; 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) { @@ -2593,7 +2598,13 @@ virDomainNetDefParseXML(virCapsPtr caps, } } + if (virXPathULong("string(./tune/sndbuf)", ctxt,&sndbuf)>= 0) { + def->tune.sndbuf = sndbuf; + def->tune.sndbuf_specified = 1; + }This is parsing a 'long'@@ -6315,6 +6336,12 @@ virDomainNetDefFormat(virBufferPtr buf, VIR_FREE(attrs); } + if (def->tune.sndbuf_specified) { + virBufferAddLit(buf, "<tune>\n"); + virBufferVSprintf(buf, "<sndbuf>%d</sndbuf>\n", def->tune.sndbuf); + virBufferAddLit(buf, "</tune>\n"); + }But this is printing an int
Yeah, the problem was that I needed to generate the value both with a virXPath*() function (which only had something to return a long) as well as with a conversion from string (and virStrToLong_*() could only give me an int. So either way I was out of luck. eblake came to the rescue with a patch that rounds out both function sets to do both types, so I'm going to make it an unsigned long.
Also bitfields should be 'unsigned' rather than int, otherwise you're actually storing 0 and -1 as possible values, rather than 0& 1. Or alternatively could just use a 'bool' here. Since there's only one bitfield, padding means we're not saving any space.
My first instinct was to make it a bool, but I saw cases of others using int bitfields for the same purpose, and nobody using bool; I decided to conform to existing practice.
If it's okay with you to make it a bool, that's what I'll do in v2. -- libvir-list mailing list libvir-list@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/libvir-list