Thanks for continuing to dig into this.
Comparing your nova-compute logs and the strace unlink details, the timestamps do seem to point to unlink causing the delay. Pasting the strace unlink output below inline with the nova-compute logs in order of occurrence:
nova-compute log: 2018-04-25 14:48:04.587 54255 INFO nova.virt.libvirt.driver [req-85551d96-713d-499d-b7ff-9f911fb0842d bc0ab055427645aca4ed09266e85b1db 1cb457a8302543fea067e5f14b5241e7 - - -] [instance: bd17aeef-240b-489c-8bb6-b37167155174] Deleting instance files /srv/nova/instances/bd17aeef-240b-489c-8bb6-b37167155174_del
strace unlink: 54255 14:48:04.593792 unlink("/srv/nova/instances/bd17aeef-240b-489c-8bb6-b37167155174_del/disk" <unfinished ...>
strace unlink: 54255 14:52:06.349167 <... unlink resumed> ) = 0 54255 14:52:06.349430 unlink("/srv/nova/instances/bd17aeef-240b-489c-8bb6-b37167155174_del/disk.info") = 0
nova-compute log: 2018-04-25 14:52:06.350 54255 INFO nova.virt.libvirt.driver [req-85551d96-713d-499d-b7ff-9f911fb0842d bc0ab055427645aca4ed09266e85b1db 1cb457a8302543fea067e5f14b5241e7 - - -] [instance: bd17aeef-240b-489c-8bb6-b37167155174] Deletion of /srv/nova/instances/bd17aeef-240b-489c-8bb6-b37167155174_del complete
This might be worth passing by kernel folks to get their opinion.
Thanks for continuing to dig into this.
Comparing your nova-compute logs and the strace unlink details, the timestamps do seem to point to unlink causing the delay. Pasting the strace unlink output below inline with the nova-compute logs in order of occurrence:
nova-compute log: libvirt. driver [req-85551d96- 713d-499d- b7ff-9f911fb084 2d bc0ab055427645a ca4ed09266e85b1 db 1cb457a8302543f ea067e5f14b5241 e7 - - -] [instance: bd17aeef- 240b-489c- 8bb6-b371671551 74] Deleting instance files /srv/nova/ instances/ bd17aeef- 240b-489c- 8bb6-b371671551 74_del
2018-04-25 14:48:04.587 54255 INFO nova.virt.
strace unlink: "/srv/nova/ instances/ bd17aeef- 240b-489c- 8bb6-b371671551 74_del/ disk" <unfinished ...>
54255 14:48:04.593792 unlink(
strace unlink: "/srv/nova/ instances/ bd17aeef- 240b-489c- 8bb6-b371671551 74_del/ disk.info" ) = 0
54255 14:52:06.349167 <... unlink resumed> ) = 0
54255 14:52:06.349430 unlink(
nova-compute log: libvirt. driver [req-85551d96- 713d-499d- b7ff-9f911fb084 2d bc0ab055427645a ca4ed09266e85b1 db 1cb457a8302543f ea067e5f14b5241 e7 - - -] [instance: bd17aeef- 240b-489c- 8bb6-b371671551 74] Deletion of /srv/nova/ instances/ bd17aeef- 240b-489c- 8bb6-b371671551 74_del complete
2018-04-25 14:52:06.350 54255 INFO nova.virt.
This might be worth passing by kernel folks to get their opinion.