Hi,
I have an instance with 8G ram assigned. All block devices have cache
disabled (cache=none) on host. However, cgroup is reporting 4G of
cache associated to the instance (on host)
# cgget -r memory.stat libvirt/qemu/i-000009fa
libvirt/qemu/i-000009fa:
memory.stat: cache 4318011392
rss 8676360192
...
When I drop all system caches on host..
# echo 3 > /proc/sys/vm/drop_caches
#
..cache associated to the instance drops too.
# cgget -r memory.stat libvirt/qemu/i-000009fa
libvirt/qemu/i-000009fa:
memory.stat: cache 122880
rss 8674291712
...
Can somebody explain what is cached, if there is cache=none everywhere ?
Thanks,
Brano Zarnovican
PS: versions:
Scientific Linux release 6.4 (Carbon)
kernel-2.6.32-358.11.1.el6.x86_64
qemu-kvm-0.12.1.2-2.355.el6_4.5.x86_64
libvirt-0.10.2-18.el6_4.5.x86_64
[root@dev-cmp08 ~]# ps auxw | head -1
USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND
[root@dev-cmp08 ~]# ps auxw | grep 12007
qemu 12007 72.8 1.5 13751712 8462604 ? Sl Jul08 31441:33 /usr/libexec/qemu-kvm -name i-000009fa -S -M rhel6.3.0 -cpu SandyBridge,+pdpe1gb,+osxsave,+dca,+pcid,+pdcm,+xtpr,+tm2,+est,+smx,+vmx,+ds_cpl,+monitor,+dtes64,+pbe,+tm,+ht,+ss,+acpi,+ds,+vme -enable-kvm -m 8196 -smp 8,sockets=8,cores=1,threads=1 -uuid 23e7ad1f-e79d-41d0-bbf5-a2f95c26c1da -nodefconfig -nodefaults -chardev socket,id=charmonitor,path=/var/lib/libvirt/qemu/i-000009fa.monitor,server,nowait -mon chardev=charmonitor,id=monitor,mode=control -rtc base=utc -no-shutdown -device piix3-usb-uhci,id=usb,bus=pci.0,addr=0x1.0x2 -drive file=/var/lib/nova/instances/i-000009fa/disk,if=none,id=drive-virtio-disk0,format=qcow2,cache=none -device virtio-blk-pci,scsi=off,bus=pci.0,addr=0x4,drive=drive-virtio-disk0,id=virtio-disk0,bootindex=1 -drive file=/var/lib/nova/instances/i-000009fa/disk.local,if=none,id=drive-virtio-disk1,format=qcow2,cache=none -device virtio-blk-pci,scsi=off,bus=pci.0,addr=0x5,drive=drive-virtio-disk1,id=virtio-disk1 -drive file=/dev/disk/by-path/ip-172.30.128.3:3260-iscsi-iqn.1992-08.com.netapp:node.netapp02-lun-14,if=none,id=drive-virtio-disk5,format=raw,cache=none -device virtio-blk-pci,scsi=off,bus=pci.0,addr=0x7,drive=drive-virtio-disk5,id=virtio-disk5 -netdev tap,fd=21,id=hostnet0,vhost=on,vhostfd=24 -device virtio-net-pci,netdev=hostnet0,id=net0,mac=fa:16:3e:4f:02:ea,bus=pci.0,addr=0x3 -chardev file,id=charserial0,path=/var/lib/nova/instances/i-000009fa/console.log -device isa-serial,chardev=charserial0,id=serial0 -chardev pty,id=charserial1 -device isa-serial,chardev=charserial1,id=serial1 -device usb-tablet,id=input0 -vnc 172.30.129.221:2 -k en-us -vga cirrus -device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x6
root 12012 0.5 0.0 0 0 ? S Jul08 225:22 [vhost-12007]
root 49616 0.0 0.0 103244 852 pts/23 S+ 12:31 0:00 grep 12007
[root@dev-cmp08 ~]#
[root@dev-cmp08 ~]#
[root@dev-cmp08 ~]#
[root@dev-cmp08 ~]# cgget -r memory.limit_in_bytes -r memory.usage_in_bytes libvirt/qemu/i-000009fa
libvirt/qemu/i-000009fa:
memory.limit_in_bytes: 13215727616
memory.usage_in_bytes: 12998287360
[root@dev-cmp08 ~]# virsh dumpxml i-000009fa
<domain type='kvm' id='3'>
<name>i-000009fa</name>
<uuid>23e7ad1f-e79d-41d0-bbf5-a2f95c26c1da</uuid>
<memory unit='KiB'>8392704</memory>
<currentMemory unit='KiB'>8392704</currentMemory>
<vcpu placement='static'>8</vcpu>
<os>
<type arch='x86_64' machine='rhel6.3.0'>hvm</type>
<boot dev='hd'/>
</os>
<features>
<acpi/>
<apic/>
<pae/>
</features>
<cpu mode='custom' match='exact'>
<model fallback='allow'>SandyBridge</model>
<vendor>Intel</vendor>
<feature policy='require' name='pdpe1gb'/>
<feature policy='require' name='osxsave'/>
<feature policy='require' name='dca'/>
<feature policy='require' name='pcid'/>
<feature policy='require' name='pdcm'/>
<feature policy='require' name='xtpr'/>
<feature policy='require' name='tm2'/>
<feature policy='require' name='est'/>
<feature policy='require' name='smx'/>
<feature policy='require' name='vmx'/>
<feature policy='require' name='ds_cpl'/>
<feature policy='require' name='monitor'/>
<feature policy='require' name='dtes64'/>
<feature policy='require' name='pbe'/>
<feature policy='require' name='tm'/>
<feature policy='require' name='ht'/>
<feature policy='require' name='ss'/>
<feature policy='require' name='acpi'/>
<feature policy='require' name='ds'/>
<feature policy='require' name='vme'/>
</cpu>
<clock offset='utc'/>
<on_poweroff>destroy</on_poweroff>
<on_reboot>restart</on_reboot>
<on_crash>destroy</on_crash>
<devices>
<emulator>/usr/libexec/qemu-kvm</emulator>
<disk type='file' device='disk'>
<driver name='qemu' type='qcow2' cache='none'/>
<source file='/var/lib/nova/instances/i-000009fa/disk'/>
<target dev='vda' bus='virtio'/>
<alias name='virtio-disk0'/>
<address type='pci' domain='0x0000' bus='0x00' slot='0x04' function='0x0'/>
</disk>
<disk type='file' device='disk'>
<driver name='qemu' type='qcow2' cache='none'/>
<source file='/var/lib/nova/instances/i-000009fa/disk.local'/>
<target dev='vdb' bus='virtio'/>
<alias name='virtio-disk1'/>
<address type='pci' domain='0x0000' bus='0x00' slot='0x05' function='0x0'/>
</disk>
<disk type='block' device='disk'>
<driver name='qemu' type='raw' cache='none'/>
<source dev='/dev/disk/by-path/ip-172.30.128.3:3260-iscsi-iqn.1992-08.com.netapp:node.netapp02-lun-14'/>
<target dev='sdf' bus='virtio'/>
<alias name='virtio-disk5'/>
<address type='pci' domain='0x0000' bus='0x00' slot='0x07' function='0x0'/>
</disk>
<controller type='usb' index='0'>
<alias name='usb0'/>
<address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x2'/>
</controller>
<interface type='bridge'>
<mac address='fa:16:3e:4f:02:ea'/>
<source bridge='br_v101'/>
<target dev='vnet2'/>
<model type='virtio'/>
<filterref filter='nova-instance-i-000009fa-fa163e4f02ea'>
<parameter name='DHCPSERVER' value='172.30.40.175'/>
<parameter name='IP' value='172.30.40.181'/>
</filterref>
<alias name='net0'/>
<address type='pci' domain='0x0000' bus='0x00' slot='0x03' function='0x0'/>
</interface>
<serial type='file'>
<source path='/var/lib/nova/instances/i-000009fa/console.log'/>
<target port='0'/>
<alias name='serial0'/>
</serial>
<serial type='pty'>
<source path='/dev/pts/2'/>
<target port='1'/>
<alias name='serial1'/>
</serial>
<console type='file'>
<source path='/var/lib/nova/instances/i-000009fa/console.log'/>
<target type='serial' port='0'/>
<alias name='serial0'/>
</console>
<input type='tablet' bus='usb'>
<alias name='input0'/>
</input>
<input type='mouse' bus='ps2'/>
<graphics type='vnc' port='5902' autoport='yes' listen='172.30.129.221' keymap='en-us'>
<listen type='address' address='172.30.129.221'/>
</graphics>
<video>
<model type='cirrus' vram='9216' heads='1'/>
<alias name='video0'/>
<address type='pci' domain='0x0000' bus='0x00' slot='0x02' function='0x0'/>
</video>
<memballoon model='virtio'>
<alias name='balloon0'/>
<address type='pci' domain='0x0000' bus='0x00' slot='0x06' function='0x0'/>
</memballoon>
</devices>
<seclabel type='dynamic' model='selinux' relabel='yes'>
<label>system_u:system_r:svirt_t:s0:c248,c684</label>
<imagelabel>system_u:object_r:svirt_image_t:s0:c248,c684</imagelabel>
</seclabel>
</domain>
[root@dev-cmp08 ~]# cgget -r memory.stat libvirt/qemu/i-000009fa
libvirt/qemu/i-000009fa:
memory.stat: cache 4318011392
rss 8676360192
mapped_file 20480
pgpgin 16765353
pgpgout 17492340
swap 921600
inactive_anon 1866690560
active_anon 6809690112
inactive_file 2909306880
active_file 1408684032
unevictable 0
hierarchical_memory_limit 13215727616
hierarchical_memsw_limit 9223372036854775807
total_cache 4318011392
total_rss 8676360192
total_mapped_file 20480
total_pgpgin 16765353
total_pgpgout 17492340
total_swap 921600
total_inactive_anon 1866690560
total_active_anon 6809690112
total_inactive_file 2909306880
total_active_file 1408684032
total_unevictable 0
[root@dev-cmp08 ~]# free -m
total used free shared buffers cached
Mem: 516809 361926 154882 0 465 4860
-/+ buffers/cache: 356600 160208
Swap: 102399 2438 99961
[root@dev-cmp08 ~]#
[root@dev-cmp08 ~]#
[root@dev-cmp08 ~]#
;
; cache dropped
;
[root@dev-cmp08 ~]# echo 3 > /proc/sys/vm/drop_caches
[root@dev-cmp08 ~]# cgget -r memory.limit_in_bytes -r memory.usage_in_bytes libvirt/qemu/i-000009fa
libvirt/qemu/i-000009fa:
memory.limit_in_bytes: 13215727616
memory.usage_in_bytes: 8675569664
[root@dev-cmp08 ~]# cgget -r memory.stat libvirt/qemu/i-000009fa
libvirt/qemu/i-000009fa:
memory.stat: cache 122880
rss 8674291712
mapped_file 20480
pgpgin 16765443
pgpgout 18547107
swap 921600
inactive_anon 1865596928
active_anon 6808715264
inactive_file 24576
active_file 77824
unevictable 0
hierarchical_memory_limit 13215727616
hierarchical_memsw_limit 9223372036854775807
total_cache 122880
total_rss 8674291712
total_mapped_file 20480
total_pgpgin 16765443
total_pgpgout 18547107
total_swap 921600
total_inactive_anon 1865596928
total_active_anon 6808715264
total_inactive_file 24576
total_active_file 77824
total_unevictable 0
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