On Wed, Jun 29, 2011 at 09:20:03AM -0500, Anthony Liguori wrote:
> Sorry, I meant having a new cache option (maybe diskcache). Semantics
> would be:
>
> diskcache=on,wce=on0
> diskcache=on,wce=off O_SYNC
> diskcache=off,wce=on O_DIRECT
> diskcache=off,wce=off O_DIRECT | O_SYNC
>
> ignore
On Wed, Jun 29, 2011 at 3:13 PM, Anthony Liguori wrote:
> On 06/29/2011 08:50 AM, Christoph Hellwig wrote:
>>
>> On Wed, Jun 29, 2011 at 07:23:31AM -0500, Anthony Liguori wrote:
>>>
>>> Which file system on the host?
>>
>> Any filesystem. Although extN and btrfs are particularly bad.
>>
>>> At an
On Wed, Jun 29, 2011 at 06:17:02PM +0400, Michael Tokarev wrote:
> > Honestly, I don't know. Usually the problem is resolved with setting a
> > different cache option, so nobody bothers to ask for details. I'd guess
> > that it's ext4 in most cases.
>
> Extremly poor performance also happens on ra
On 06/29/2011 09:52 AM, Christoph Hellwig wrote:
On Wed, Jun 29, 2011 at 09:20:03AM -0500, Anthony Liguori wrote:
Sorry, I meant having a new cache option (maybe diskcache). Semantics
would be:
diskcache=on,wce=on0
diskcache=on,wce=off O_SYNC
diskcache=off,wce=on O_DIRECT
diskcache=off
29.06.2011 18:50, Christoph Hellwig wrote:
> On Wed, Jun 29, 2011 at 06:17:02PM +0400, Michael Tokarev wrote:
>>> Honestly, I don't know. Usually the problem is resolved with setting a
>>> different cache option, so nobody bothers to ask for details. I'd guess
>>> that it's ext4 in most cases.
>>
>
29.06.2011 16:32, Kevin Wolf wrote:
> Am 29.06.2011 14:23, schrieb Anthony Liguori:
>> On 06/29/2011 07:16 AM, Kevin Wolf wrote:
>>> No, people are also complaining about bad performance with raw. Which
>>> isn't really surprising when you do a flush after each single write
>>> request. O_SYNC is
On Wed, Jun 29, 2011 at 04:11:53PM +0200, Kevin Wolf wrote:
> If the guest is acting correctly, then this assumption is definitely
> true with cache=none/writeback. What needs to happen is that the guest
> issues a disk flush before sending your "transaction ok" message. If it
> doesn't do that it
Am 29.06.2011 15:53, schrieb Frediano Ziglio:
> 2011/6/29 Anthony Liguori :
>> On 06/29/2011 07:16 AM, Kevin Wolf wrote:
>>>
>>> Am 29.06.2011 14:06, schrieb Anthony Liguori:
On 06/29/2011 06:59 AM, Kevin Wolf wrote:
>
> Hi,
>
> I think we have touched this topic before du
On Wed, Jun 29, 2011 at 09:13:35AM -0500, Anthony Liguori wrote:
> Is WCE ever persisted by a disk? Would it make sense to have a mechanism
> to persist the WCE setting for a guest?
Only for SCSI, which has persistant mode pages. For ATA I've not found
a way to make it persistent yet.
2011/6/29 Anthony Liguori :
> On 06/29/2011 07:16 AM, Kevin Wolf wrote:
>>
>> Am 29.06.2011 14:06, schrieb Anthony Liguori:
>>>
>>> On 06/29/2011 06:59 AM, Kevin Wolf wrote:
Hi,
I think we have touched this topic before during some IRC discussions or
somewhere deep in a mai
On Wed, Jun 29, 2011 at 07:23:31AM -0500, Anthony Liguori wrote:
> Which file system on the host?
Any filesystem. Although extN and btrfs are particularly bad.
> At any rate, I'm a big fan of making wce tunable in the guest and then I
> think setting wce=1 is quite reasonable to do by default.
On 06/29/2011 08:55 AM, Christoph Hellwig wrote:
On Wed, Jun 29, 2011 at 07:08:18AM -0500, Anthony Liguori wrote:
As long as we advertise wce and wce can be toggled from the guest, I don't
think the default is all that important. I think cache=on is the right
default for most common use cases.
Am 29.06.2011 16:12, schrieb Christoph Hellwig:
> On Wed, Jun 29, 2011 at 04:11:53PM +0200, Kevin Wolf wrote:
>> If the guest is acting correctly, then this assumption is definitely
>> true with cache=none/writeback. What needs to happen is that the guest
>> issues a disk flush before sending your
On 29.06.2011, at 15:57, Stefan Hajnoczi wrote:
> On Wed, Jun 29, 2011 at 1:21 PM, Alexander Graf wrote:
>> On 29.06.2011, at 13:59, Kevin Wolf wrote:
>>> I'm not entirely sure if I should suggest writeback or none as the new
>>> default, but I think it could make sense to change it.
>>
>> None
On Wed, Jun 29, 2011 at 01:52:19PM +0100, Stefan Hajnoczi wrote:
> Whether it is safe to transition to cache=none or not depends on what
> broken guests are still widely deployed. Does CentOS 5 flush the disk
> cache?
Unless you use ext3 it does. The same unfortunate story still applies to
curre
On Wed, Jun 29, 2011 at 1:21 PM, Alexander Graf wrote:
> On 29.06.2011, at 13:59, Kevin Wolf wrote:
>> I'm not entirely sure if I should suggest writeback or none as the new
>> default, but I think it could make sense to change it.
>
> None as default would be a bad choice, as not all underlying f
On 06/29/2011 08:50 AM, Christoph Hellwig wrote:
On Wed, Jun 29, 2011 at 07:23:31AM -0500, Anthony Liguori wrote:
Which file system on the host?
Any filesystem. Although extN and btrfs are particularly bad.
At any rate, I'm a big fan of making wce tunable in the guest and then I
think setti
On Wed, Jun 29, 2011 at 07:08:18AM -0500, Anthony Liguori wrote:
> As long as we advertise wce and wce can be toggled from the guest, I don't
> think the default is all that important. I think cache=on is the right
> default for most common use cases.
What do you mean with cache=on? We have
ca
On 06/29/2011 04:05 PM, Anthony Liguori wrote:
So long as -M old retains the old behaviour, I'm in favour.
wce needs to be preserved but cache wouldn't need to be AFAICT.
Right.
--
error compiling committee.c: too many arguments to function
On Wed, Jun 29, 2011 at 02:32:34PM +0200, Kevin Wolf wrote:
> Christoph, it looks like we're back to your WCE patches then. Do you
> still work on them?
The IDE patch is ready once the bdrv_reopen from the hostcache patches
goes in. Virtio still needs to be redesigned to use a command instead
of
On 06/29/2011 02:59 PM, Kevin Wolf wrote:
Hi,
I think we have touched this topic before during some IRC discussions or
somewhere deep in a mailing list thread, but I think it hasn't been
discussed on the list.
Our default cache mode of cache=writethrough is extremely conservative
and provides a
On Wed, Jun 29, 2011 at 07:06:03AM -0500, Anthony Liguori wrote:
> But for the most part, we track bare metal fairly well in terms of block
> performance, no?
only if using cache=none and fmt=raw on either a blockdevice or a fully
preallocated (not fallocated) file on a modern filesystem.
On Wed, Jun 29, 2011 at 12:59 PM, Kevin Wolf wrote:
> I'm not entirely sure if I should suggest writeback or none as the new
> default, but I think it could make sense to change it.
I agree that cache=none is safe and fast with correct guests and local
disks. It is beaten by cache=writeback in c
Am 29.06.2011 14:23, schrieb Anthony Liguori:
> On 06/29/2011 07:16 AM, Kevin Wolf wrote:
>> Am 29.06.2011 14:06, schrieb Anthony Liguori:
>>> On 06/29/2011 06:59 AM, Kevin Wolf wrote:
Hi,
I think we have touched this topic before during some IRC discussions or
somewhere deep in
On 06/29/2011 08:00 AM, Avi Kivity wrote:
On 06/29/2011 02:59 PM, Kevin Wolf wrote:
Hi,
I think we have touched this topic before during some IRC discussions or
somewhere deep in a mailing list thread, but I think it hasn't been
discussed on the list.
Our default cache mode of cache=writethrou
Am 29.06.2011 15:00, schrieb Avi Kivity:
> On 06/29/2011 02:59 PM, Kevin Wolf wrote:
>> Hi,
>>
>> I think we have touched this topic before during some IRC discussions or
>> somewhere deep in a mailing list thread, but I think it hasn't been
>> discussed on the list.
>>
>> Our default cache mode of
Am 29.06.2011 14:06, schrieb Anthony Liguori:
> On 06/29/2011 06:59 AM, Kevin Wolf wrote:
>> Hi,
>>
>> I think we have touched this topic before during some IRC discussions or
>> somewhere deep in a mailing list thread, but I think it hasn't been
>> discussed on the list.
>>
>> Our default cache mo
On 06/29/2011 07:16 AM, Kevin Wolf wrote:
Am 29.06.2011 14:06, schrieb Anthony Liguori:
On 06/29/2011 06:59 AM, Kevin Wolf wrote:
Hi,
I think we have touched this topic before during some IRC discussions or
somewhere deep in a mailing list thread, but I think it hasn't been
discussed on the li
On 06/29/2011 06:59 AM, Kevin Wolf wrote:
Hi,
I think we have touched this topic before during some IRC discussions or
somewhere deep in a mailing list thread, but I think it hasn't been
discussed on the list.
Our default cache mode of cache=writethrough is extremely conservative
and provides a
On 06/29/2011 06:59 AM, Kevin Wolf wrote:
Hi,
I think we have touched this topic before during some IRC discussions or
somewhere deep in a mailing list thread, but I think it hasn't been
discussed on the list.
Our default cache mode of cache=writethrough is extremely conservative
and provides a
On 29.06.2011, at 13:59, Kevin Wolf wrote:
> Hi,
>
> I think we have touched this topic before during some IRC discussions or
> somewhere deep in a mailing list thread, but I think it hasn't been
> discussed on the list.
>
> Our default cache mode of cache=writethrough is extremely conservative
Hi,
I think we have touched this topic before during some IRC discussions or
somewhere deep in a mailing list thread, but I think it hasn't been
discussed on the list.
Our default cache mode of cache=writethrough is extremely conservative
and provides absolute safety at the cost of performance, a
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