From 3e4c5a6261770bced301b5e74233e7866166ea5b Mon Sep 17 00:00:00 2001 From: Christian Krinitsin Date: Sun, 1 Jun 2025 21:35:14 +0200 Subject: clean up repository --- .../target_missing/host_missing/accel_missing/1307 | 72 ---------------------- 1 file changed, 72 deletions(-) delete mode 100644 gitlab/issues_text/target_missing/host_missing/accel_missing/1307 (limited to 'gitlab/issues_text/target_missing/host_missing/accel_missing/1307') diff --git a/gitlab/issues_text/target_missing/host_missing/accel_missing/1307 b/gitlab/issues_text/target_missing/host_missing/accel_missing/1307 deleted file mode 100644 index 9e90d8ad4..000000000 --- a/gitlab/issues_text/target_missing/host_missing/accel_missing/1307 +++ /dev/null @@ -1,72 +0,0 @@ -query-named-block-nodes, without flat=true, is massively slow as number of block nodes increases -Description of problem: -The query-named-block-nodes command is insanely slow with deep backing chains when the flat=true arg is NOT given. - -``` -qemu-img create demo0.qcow2 1g -j=0 -for i in `seq 1 199` -do - qemu-img create -f qcow2 -o backing_file=demo$j.qcow2 -o backing_fmt=qcow2 demo$i.qcow2 - j=$i -done -``` - -Now configure libvirt with - -``` - - - - -
- -``` - -This results in `-blockdev` args - -``` --blockdev '{"driver":"file","filename":"/var/lib/libvirt/images/demo0.qcow2","node-name":"libvirt-201-storage","auto-read-only":true,"discard":"unmap"}' \ --blockdev '{"node-name":"libvirt-201-format","read-only":true,"discard":"unmap","driver":"qcow2","file":"libvirt-201-storage","backing":null}' \ --blockdev '{"driver":"file","filename":"/var/lib/libvirt/images/demo1.qcow2","node-name":"libvirt-200-storage","auto-read-only":true,"discard":"unmap"}' \ --blockdev '{"node-name":"libvirt-200-format","read-only":true,"discard":"unmap","driver":"qcow2","file":"libvirt-200-storage","backing":"libvirt-201-format"}' \ --blockdev '{"driver":"file","filename":"/var/lib/libvirt/images/demo2.qcow2","node-name":"libvirt-199-storage","auto-read-only":true,"discard":"unmap"}' \ --blockdev '{"node-name":"libvirt-199-format","read-only":true,"discard":"unmap","driver":"qcow2","file":"libvirt-199-storage","backing":"libvirt-200-format"}' \ -...snip... --blockdev '{"driver":"file","filename":"/var/lib/libvirt/images/demo197.qcow2","node-name":"libvirt-4-storage","auto-read-only":true,"discard":"unmap"}' \ --blockdev '{"node-name":"libvirt-4-format","read-only":true,"discard":"unmap","driver":"qcow2","file":"libvirt-4-storage","backing":"libvirt-5-format"}' \ --blockdev '{"driver":"file","filename":"/var/lib/libvirt/images/demo198.qcow2","node-name":"libvirt-3-storage","auto-read-only":true,"discard":"unmap"}' \ --blockdev '{"node-name":"libvirt-3-format","read-only":true,"discard":"unmap","driver":"qcow2","file":"libvirt-3-storage","backing":"libvirt-4-format"}' \ --blockdev '{"driver":"file","filename":"/var/lib/libvirt/images/demo199.qcow2","node-name":"libvirt-1-storage","auto-read-only":true,"discard":"unmap"}' \ --blockdev '{"node-name":"libvirt-1-format","read-only":false,"discard":"unmap","driver":"qcow2","file":"libvirt-1-storage","backing":"libvirt-3-format"}' \ --device '{"driver":"virtio-blk-pci","bus":"pci.7","addr":"0x0","drive":"libvirt-1-format","id":"virtio-disk1"}' \ -``` - -Now stop libvirt - -``` -systemctl stop libvirtd -``` - -And speak directly to QMP - -``` -$ time socat UNIX:/var/lib/libvirt/qemu/domain-158-fedora38/monitor.sock - > /dev/null -{ "execute": "qmp_capabilities", "arguments": { "enable": ["oob"] } } -{ "execute": "query-named-block-nodes"} -{ "execute": "quit" } - -real 2m19.276s -user 0m0.006s -sys 0m0.014s -``` - -If we save the 'query-named-block-nodes' output instead of sending it to /dev/null, we get a 86 MB file for the QMP response. This will break all known client apps since they limit QMP reply size. - -It appears to have a combinatorial expansion of block nodes in the output. - -Blocking the main event loop for 2 minutes is obviously not good either. - -If we use '"flat": true' parameter to query-named-block-nodes, the command completes in just 15 seconds, and produces a large, but more manageable 2.7 MB - -Since the non-flat query-named-block-nodes output is so incredibly non-scalable, I think we should deprecate non-flat mode, and eventually make flat the mandatory option. -- cgit 1.4.1