Re: [PATCH v2 2/3] conf, docs: Add support for coalesce setting(s)

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On Fri, Apr 21, 2017 at 11:19:36AM +0200, Michal Privoznik wrote:
On 04/20/2017 02:21 PM, Martin Kletzander wrote:
We are currently parsing only rx_max_coalesced_frames because that's
the only value that makes sense for us.  The tun device just added
support for this one and the others are only supported by hardware
devices which we don't need to worry about as the only way we'd pass
those to the domain is using <hostdev/> or <interface type='hostdev'/>.
And in those cases the guest can modify the settings itself.

Signed-off-by: Martin Kletzander <mkletzan@xxxxxxxxxx>
---
 docs/formatdomain.html.in                          |  24 ++++
 docs/schemas/domaincommon.rng                      | 131 +++++++++++++++++++++
 src/conf/domain_conf.c                             |  80 +++++++++++++
 src/conf/domain_conf.h                             |   2 +
 src/qemu/qemu_domain.c                             |  31 +++++
 .../qemuxml2argvdata/qemuxml2argv-net-coalesce.xml |  68 +++++++++++
 .../qemuxml2xmlout-net-coalesce.xml                |  71 +++++++++++
 tests/qemuxml2xmltest.c                            |   1 +
 8 files changed, 408 insertions(+)
 create mode 100644 tests/qemuxml2argvdata/qemuxml2argv-net-coalesce.xml
 create mode 100644 tests/qemuxml2xmloutdata/qemuxml2xmlout-net-coalesce.xml

diff --git a/docs/formatdomain.html.in b/docs/formatdomain.html.in
index b1e38f00e423..ea64b7fd1193 100644
--- a/docs/formatdomain.html.in
+++ b/docs/formatdomain.html.in
@@ -5405,6 +5405,30 @@ qemu-kvm -net nic,model=? /dev/null
       <span class="since">Since 3.1.0</span>
     </p>

+    <h5><a name="coalesce">Coalesce settings</a></h5>
+<pre>
+...
+&lt;devices&gt;
+  &lt;interface type='network'&gt;
+    &lt;source network='default'/&gt;
+    &lt;target dev='vnet0'/&gt;
+    <b>&lt;coalesce&gt;
+      &lt;rx_max_coalesced_frames&gt;5&lt;/rx_max_coalesced_frames&gt;
+    &lt;/coalesce&gt;</b>
+  &lt;/interface&gt;
+&lt;/devices&gt;
+...</pre>
+
+    <p>
+      This element provides means of setting coalesce settings for some
+      interface devices (currently only type <code>network</code>
+      and <code>bridge</code>.  Currently there is just one sub-element
+      named <code>rx_max_coalesced_frames</code> which accepts a non-negative
+      integer that specifies the maximum number of packets that will be received
+      before an interrupt.
+      <span class="since">Since 3.3.0</span>
+    </p>
This does not correspond to the schema or tests introduced later in the
patch.

Good catch, thanks for noticing.

diff --git a/src/conf/domain_conf.c b/src/conf/domain_conf.c
index 705deb39a1bf..cbeebdc56880 100644
--- a/src/conf/domain_conf.c
+++ b/src/conf/domain_conf.c
@@ -6772,6 +6772,77 @@ virDomainNetIPInfoParseXML(const char *source,
     return ret;
 }

+
+static virNetDevCoalescePtr
+virDomainNetDefCoalesceParseXML(xmlNodePtr node,
+                                xmlXPathContextPtr ctxt)
+{
+    virNetDevCoalescePtr ret = NULL;
+    xmlNodePtr save = NULL;
+    char *str = NULL;
+    unsigned long long tmp = 0;
+
+    save = ctxt->node;
+    ctxt->node = node;
+
+    str = virXPathString("string(./rx/frames/@max)", ctxt);
+    if (!str)
+        goto cleanup;
+
+    if (!ret && VIR_ALLOC(ret) < 0)
+        goto cleanup;
+
+    if (virStrToLong_ullp(str, NULL, 10, &tmp) < 0) {
+        virReportError(VIR_ERR_XML_DETAIL,
+                       _("cannot parse value '%s' for coalesce parameter"),
+                       str);
+        VIR_FREE(str);
+        goto error;
+    }
+    VIR_FREE(str);
+
+    if (tmp > UINT32_MAX) {
+        virReportError(VIR_ERR_OVERFLOW,
+                       _("value '%llu' is too big for coalesce "
+                         "parameter, maximum is '%lu'"),
+                       tmp, (unsigned long) UINT32_MAX);
+        goto error;
+    }
+    ret->rx_max_coalesced_frames = tmp;
I wonder if we can turn this into a macro (despite some of us hating
them) because potentially we'll parse all the 32 coalesce attributes (or
how many there are). But for now, this is okay as is.

I did that.  Multiple times.  GET_COAL(rx, frames, max) for example and
I tried various ways how to do that so it's nicely extensible.  But
after a while I gave up because it would be used once and whatever.
Maybe nobody will ever want to add any other parameter...

+
+ cleanup:
+    ctxt->node = save;
+    return ret;
+
+ error:
+    VIR_FREE(ret);
+    goto cleanup;
+}
Michal

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