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[Qemu-devel] [Bug 1609968] Re: "cannot set up guest memory" b/c no autom
From: |
Celmor |
Subject: |
[Qemu-devel] [Bug 1609968] Re: "cannot set up guest memory" b/c no automatic clearing of Linux' cache |
Date: |
Mon, 08 Aug 2016 23:39:44 -0000 |
@dgilbert-h / Dr. David Alan Gilbert
Thanks for your answer.
b)
Mounted/used block devices:
NAME MOUNTPOINT TYPE FSTYPE
sda disk crypto_LUKS
└─Data1 crypt zfs_member
├─sdb5 / part ext4
└─sdb6 /boot part vfat
sdd disk crypto_LUKS
└─Data2 crypt zfs_member
ZFS file system for extra space, also ZFS is the reason I'm not running the
latest kernel...
a)
$ free
total used free shared buff/cache available
Mem: 16379476 7879216 1867196 188180 6633064 3587620
Swap: 0 0 0
$ qemu.sh -m 10240 && echo success || echo failed
qemu-system-x86_64: cannot set up guest memory 'pc.ram': Cannot allocate memory
failed
$ sudo sh -c 'echo 1 > /proc/sys/vm/overcommit_memory'
$ qemu.sh -m 10240 && echo success || echo failed
success
So setting /proc/sys/vm/overcommit_memory to 1 works, so I guess I'm gonna need
to execute
sudo sh -c 'echo 1 > /proc/sys/vm/overcommit_memory'
at start of my qemu.sh script instead of the 'drop_caches' part.
I still think the kernel should do whatever function overcommit_memory is for
automatically, bit it seams to be the fault of the kernel of my distribution
then, thanks for your help.
--
You received this bug notification because you are a member of qemu-
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https://bugs.launchpad.net/bugs/1609968
Title:
"cannot set up guest memory" b/c no automatic clearing of Linux' cache
Status in QEMU:
New
Bug description:
Version: qemu-2.6.0-1
Kernel: 4.4.13-1-MANJARO
Full script (shouldn't matter though): https://pastebin.com/Hp24PWNE
Problem:
When host has been up and used for a while cache has been filled as much that
guest can't be started without droping caches.
Expected behavior:
Qemu should be able to request as much Memory as it needs and cause Linux to
drop cache pages if needed. A user shouldn't be required to have to come to
this conclusion and having to drop caches to start Qemu with the required
amount of memory.
My fix:
Following command (as root) required before qemu start:
# sync && echo 3 > /proc/sys/vm/drop_caches
Example:
$ sudo qemu.sh -m 10240 && echo success || echo failed
qemu-system-x86_64: cannot set up guest memory 'pc.ram': Cannot allocate
memory
failed
$ free
total used free shared buff/cache
available
Mem: 16379476 9126884 3462688 148480 3789904
5123572
Swap: 0 0 0
$ sudo sh -c 'sync && echo 3 > /proc/sys/vm/drop_caches'
$ free
total used free shared buff/cache
available
Mem: 16379476 1694528 14106552 149772 578396
14256428
Swap: 0 0 0
$ sudo qemu.sh -m 10240 && echo success || echo failed
success
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