In commit 1c97aee and commit 227c185 udev rules was rewritten to use
systemd-run to run in a non-blocking mode. The problem is that it's a
bit noise, especially on machine bootup, systemd will always generate
extra logs for service start, you might see your journal full of lines
like these if you have many CPUs (each CPU generates a udev event on
boot):
...
Nov 22 22:23:05 localhost systemd[1]: Started /usr/lib/udev/kdump-udev-throttler.
Nov 22 22:23:05 localhost systemd[1]: Started /usr/lib/udev/kdump-udev-throttler.
Nov 22 22:23:05 localhost systemd[1]: Started /usr/lib/udev/kdump-udev-throttler.
Nov 22 22:23:05 localhost systemd[1]: Started /usr/lib/udev/kdump-udev-throttler.
...
While system is still booting up, kdump service is not started yet, so
systemd-run calls will end up doing nothing, the throttler being called
by systemd-run will just exit if kdump is not loaded.
This patch avoid systemd-run from being called at first place if kdump
service is not running by checking kdump.service status in udev rule,
so there won't be unnecessary logs.
Also remove the kdump service checking logic in kdump-udev-throttler as
udev is the only expected callee of this script, if it's not being
called at first place when kdump service is running, this checking will
be redundant. And even if any user called this script manually, it will
still work well as this script will call 'kdumpctl reload', it reload
the kdump resource only if kdump is loaded already.
Signed-off-by: Kairui Song <kasong@redhat.com>
Acked-by: Dave Young <dyoung@redhat.com>
Previously, kdump will restart / reload for many times on hotplug
event, especially memory hotplug events. Hotplugged memory may
generate many udev event as memory are managed and hotplugged in
small chunks by the kernel.
This results in unnecessary system workload and an actually longer
delay of kdump reload and the hotplug event, as udev will either
get blocked or kdumpctl will be waiting for other triggered operation.
To fix this, introduce a kdump-udev-throttler as an agent which will
be called by udev and merge concurrent kdump restart requests. Tested
with a Hyper-V VM which is failing due to udev timeout previously,
no new issues found.
Signed-off-by: Kairui Song <kasong@redhat.com>
Acked-by: Dave Young <dyoung@redhat.com>
