Re: [libvirt] [PATCH] nodedev_udev: Fix missing events when kernel report lots of udev events within a short time

On Tue, May 09, 2017 at 10:09:07AM +0800, ZhiPeng Lu wrote: > From: "ning.bo" <ning.bo9(a)zte.com.cn&gt; > > When create Virtual Function for Inter XL710 use below commands: > for i in `seq 0 1`; do > echo 63 > /sys/devices/pci0000:00/0000:00:03.2/0000:07:00.$i/sriov_numvfs > done > for i in `seq 0 3`; do > echo 31 > /sys/devices/pci0000:80/0000:80:02.2/0000:82:00.$i/sriov_numvfs > done > Hi, I think this is worth a BZ, so we can track and test the issue. Now, I'm working on a similar issue which is very hard to reproduce and this looks like it could be reproduced easily with 100% chance, but I don't have any HW to try it on (it might take a while to get my hands on some). So, would you mind opening a BZ for this, attaching not only libvirtd's debug logs, but preferably udev debug logs as well (libudev API is kinda poorly designed in this aspect and the only way to check for the real error is to enable the debugging and look into the logs). > The libvirtd will missing some udev events, the result of libvirt-python API > listDevices('pci') will not list all pci devices. > The reason is that the buffer of udev monitor default size cann't save all udev > events reported by kernel. > So we need change buffer size so that we can receive as much events as possible > whitin a short time. > > Signed-off-by: ning.bo <ning.bo9(a)zte.com.cn&gt; > --- > src/node_device/node_device_udev.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/src/node_device/node_device_udev.c b/src/node_device/node_device_udev.c > index 6e706a1..d813206 100644 > --- a/src/node_device/node_device_udev.c > +++ b/src/node_device/node_device_udev.c > @@ -1564,6 +1564,7 @@ static int nodeStateInitialize(bool privileged, > } > > udev_monitor_enable_receiving(priv->udev_monitor); > + udev_monitor_set_receive_buffer_size(priv->udev_monitor, 128 * 1024 * 1024); > The reason why I want to investigate the logs (ideally try it myself) is rather than blindly increasing the buffer size, maybe we receive just too many events, out of which some we might filter out and the problem would disappear. Anyhow, isn't 129 MiB bit of an overkill for a buffer size? I mean, you didn't provide any commentary on why you chose 128MiB specifically, I can only guess it somehow relates to the fact, that XL710 is capable of 128 VFs??