Free Memory In Hosts
Hi All, I have noticed that there is a huge difference between memory reading obtained from top or free commands, and values displayed on ovirt engine. "Host " Example: Engine Version : *ovirt-engine-3.4.3-1.el6.noarch* *OS: Centos 6.5_x86_64* *Used Memory:* *from free:* [root@oVirt ~]# free total used free shared buffers cached Mem: 65890412 65609864 280548 0 305408 53759412 from Egnine Webpage: only 12G is being used. Is there an explanation for this ? Please note this is the same on all previous version, the values matches only after restart of the host then free memory start to vanish by time ! Thanks, Mohyedeen.
On Wed, Sep 10, 2014 at 11:57:05PM +0300, Mohyedeen Nazzal wrote:
Hi All, I have noticed that there is a huge difference between memory reading obtained from top or free commands, and values displayed on ovirt engine. "Host "
Example: Engine Version : *ovirt-engine-3.4.3-1.el6.noarch* *OS: Centos 6.5_x86_64*
*Used Memory:* *from free:* [root@oVirt ~]# free total used free shared buffers cached Mem: 65890412 65609864 280548 0 305408 53759412
from Egnine Webpage:
only 12G is being used.
Is there an explanation for this ?
It's a Linux thing. When a file is opened, it is mapped into memory, but when it is closed Linux does not evict it before memory is released again. Thus, a long-running active host reaches 0 free mem sooner than later. For oVirt GUI, we found this misleading - there, "free" means "how much memory is available for new VMs to use". Therefore oVirt reports "buffred" and "cached" memory as free, too.
Hi, If you look at the full free output you will see another line: total used free shared buffers cached Mem: 8057004 7491980 565024 0 234592 2005452 -/+ buffers/cache: 5251936 2805068 The +/- buffers/cache tells you how much memory you will have available after you (the kernel) clean all buffers and caches. And that is the number we look at. -- Martin Sivák msivak@redhat.com Red Hat Czech RHEV-M SLA / Brno, CZ ----- Original Message -----
On Wed, Sep 10, 2014 at 11:57:05PM +0300, Mohyedeen Nazzal wrote:
Hi All, I have noticed that there is a huge difference between memory reading obtained from top or free commands, and values displayed on ovirt engine. "Host "
Example: Engine Version : *ovirt-engine-3.4.3-1.el6.noarch* *OS: Centos 6.5_x86_64*
*Used Memory:* *from free:* [root@oVirt ~]# free total used free shared buffers cached Mem: 65890412 65609864 280548 0 305408 53759412
from Egnine Webpage:
only 12G is being used.
Is there an explanation for this ?
It's a Linux thing. When a file is opened, it is mapped into memory, but when it is closed Linux does not evict it before memory is released again. Thus, a long-running active host reaches 0 free mem sooner than later.
For oVirt GUI, we found this misleading - there, "free" means "how much memory is available for new VMs to use". Therefore oVirt reports "buffred" and "cached" memory as free, too. _______________________________________________ Users mailing list Users@ovirt.org http://lists.ovirt.org/mailman/listinfo/users
participants (3)
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Dan Kenigsberg -
Martin Sivak -
Mohyedeen Nazzal