[libvirt] [PATCH 1/3] virNetDevOpenvswitchInterfaceStats: Optimize for speed
Ján Tomko
jtomko at redhat.com
Fri Jul 12 16:28:52 UTC 2019
On Wed, Jul 03, 2019 at 09:19:18AM +0200, Michal Privoznik wrote:
>We run 'ovs-vsctl' nine times (first to find if interface is
>there and then eight times = for each stats member separately).
>This is very inefficient. I've found a way to run it once and
>with a bit of help from virJSON module we can parse out stats
>we need.
>
>Signed-off-by: Michal Privoznik <mprivozn at redhat.com>
>---
> src/util/virnetdevopenvswitch.c | 111 +++++++++++++++++++++-----------
> 1 file changed, 74 insertions(+), 37 deletions(-)
>
>diff --git a/src/util/virnetdevopenvswitch.c b/src/util/virnetdevopenvswitch.c
>index c99ecfbf15..0fe64bedab 100644
>--- a/src/util/virnetdevopenvswitch.c
>+++ b/src/util/virnetdevopenvswitch.c
>@@ -28,6 +28,7 @@
> #include "virmacaddr.h"
> #include "virstring.h"
> #include "virlog.h"
>+#include "virjson.h"
>
> #define VIR_FROM_THIS VIR_FROM_NONE
>
>@@ -311,58 +312,94 @@ int
> virNetDevOpenvswitchInterfaceStats(const char *ifname,
> virDomainInterfaceStatsPtr stats)
> {
>- char *tmp;
>- bool gotStats = false;
> VIR_AUTOPTR(virCommand) cmd = NULL;
> VIR_AUTOFREE(char *) output = NULL;
>+ VIR_AUTOPTR(virJSONValue) jsonStats = NULL;
>+ virJSONValuePtr jsonMap = NULL;
>+ size_t i;
>
>- /* Just ensure the interface exists in ovs */
> cmd = virCommandNew(OVSVSCTL);
> virNetDevOpenvswitchAddTimeout(cmd);
>- virCommandAddArgList(cmd, "get", "Interface", ifname, "name", NULL);
>+ virCommandAddArgList(cmd, "--if-exists", "--format=list", "--data=json",
>+ "--no-headings", "--columns=statistics", "list",
>+ "Interface", ifname, NULL);
Can we assume these options are present in all the supported versions of
ovs-vsctl?
> virCommandSetOutputBuffer(cmd, &output);
>
>- if (virCommandRun(cmd, NULL) < 0) {
>+ /* The above command returns either:
>+ * 1) empty string if @ifname doesn't exist, or
>+ * 2) a JSON array, for instance:
>+ * ["map",[["collisions",0],["rx_bytes",0],["rx_crc_err",0],["rx_dropped",0],
>+ * ["rx_errors",0],["rx_frame_err",0],["rx_over_err",0],["rx_packets",0],
>+ * ["tx_bytes",12406],["tx_dropped",0],["tx_errors",0],["tx_packets",173]]]
>+ */
>+
This example would look better in tests/ where you test this function
against actual output O:-)
>+ if (virCommandRun(cmd, NULL) < 0 ||
>+ STREQ_NULLABLE(output, "")) {
> /* no ovs-vsctl or interface 'ifname' doesn't exists in ovs */
> virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
> _("Interface not found"));
> return -1;
> }
>
Jano
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