From: "Fabian Grünbichler" <f.gruenbichler@proxmox.com>
To: Proxmox VE user list <pve-user@lists.proxmox.com>
Subject: Re: [PVE-User] PBS : is dirty-bitmap really accurate ?
Date: Thu, 23 Jul 2020 11:34:15 +0200 [thread overview]
Message-ID: <1595496811.im826y29fq.astroid@nora.none> (raw)
In-Reply-To: <3ce2e15f-9b92-64ce-af55-a21fa46dc5d6@gmail.com>
On July 23, 2020 11:00 am, Jorge Boncompte wrote:
> El 23/7/20 a las 8:53, Daniel Berteaud escribió:
>> ----- Le 23 Juil 20, à 8:43, Fabian Grünbichler f.gruenbichler@proxmox.com a écrit :
>>
>>> possibly you haven't upgraded to pve-qemu-kvm 5.0-11 (or your VM hasn't
>>> been restarted yet since the upgrade):
>>>
>>> https://git.proxmox.com/?p=pve-qemu.git;a=commit;h=f257cc05f4fbf772cad3231021b3ce7587127a1b
>>
>> I'm running pve-qemu-kvm 5.0.0-11, and all the implied VM have been either (cold) rebooted, or migrated.
>>
>>>
>>> the bitmap has a granularity of 4MB, so depending on the activity inside
>>> you can see quite a bit of amplification. also writing and then
>>> zeroing/reverting again to the old content would leave a mark in the
>>> bitmap without permanently changing the contents.
>>>
>>
>> Yes, I'd expect some amplification, but not that much. For my Zabbix server, it's nearly canceling all the benefit of using a dirty bitmap.
>> One thing I've noted, is that I get expected values at least for one guest, running PfSense (where I get ~150MB of dirty blocks each days). Most of my other VM are Linux, I'll check if it could be related to the atime update or something
>
> Hi, does the dirty-bitmap take somehow into account block discarding
> and zeroing? Because the other thing I would look for in this case is
> for a fstrim firing every day.
also a possible candidate. trim/discard of course changes the blocks and
thus dirties the bitmap.
next prev parent reply other threads:[~2020-07-23 9:34 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-22 16:40 Daniel Berteaud
2020-07-23 6:43 ` Fabian Grünbichler
2020-07-23 6:53 ` Daniel Berteaud
2020-07-23 9:00 ` Jorge Boncompte
2020-07-23 9:34 ` Fabian Grünbichler [this message]
2020-07-23 9:40 ` Daniel Berteaud
2020-07-23 21:59 ` Roland
2020-07-24 7:02 ` Daniel Berteaud
2020-07-24 7:54 ` Ronny Aasen
2020-07-26 9:24 ` Mark Schouten
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