* Linux/x86's _PAGE_SWP_SOFT_DIRTY definition
@ 2013-08-21 7:42 Jan Beulich
2013-08-21 10:50 ` Konrad Rzeszutek Wilk
2013-08-21 11:47 ` David Vrabel
0 siblings, 2 replies; 6+ messages in thread
From: Jan Beulich @ 2013-08-21 7:42 UTC (permalink / raw)
To: David Vrabel, Boris Ostrovsky, Konrad Rzeszutek Wilk; +Cc: xen-devel
All,
was anyone of you involved in the recent (rc5->rc6) changes here?
I'm asking because this new definition conflicts with _PAGE_PAT,
which is unused only for native Linux (and I continue to not really
understand their motivation to restrict themselves to just the four
most trivial memory types).
Jan
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: Linux/x86's _PAGE_SWP_SOFT_DIRTY definition
2013-08-21 7:42 Linux/x86's _PAGE_SWP_SOFT_DIRTY definition Jan Beulich
@ 2013-08-21 10:50 ` Konrad Rzeszutek Wilk
2013-08-21 11:45 ` Jan Beulich
2013-08-21 11:47 ` David Vrabel
1 sibling, 1 reply; 6+ messages in thread
From: Konrad Rzeszutek Wilk @ 2013-08-21 10:50 UTC (permalink / raw)
To: Jan Beulich, David Vrabel, Boris Ostrovsky; +Cc: xen-devel
Jan Beulich <JBeulich@suse.com> wrote:
>All,
>
>was anyone of you involved in the recent (rc5->rc6) changes here?
>I'm asking because this new definition conflicts with _PAGE_PAT,
>which is unused only for native Linux (and I continue to not really
>understand their motivation to restrict themselves to just the four
>most trivial memory types).
>
>Jan
I have not. Does it cause regressions?
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: Linux/x86's _PAGE_SWP_SOFT_DIRTY definition
2013-08-21 10:50 ` Konrad Rzeszutek Wilk
@ 2013-08-21 11:45 ` Jan Beulich
0 siblings, 0 replies; 6+ messages in thread
From: Jan Beulich @ 2013-08-21 11:45 UTC (permalink / raw)
To: Konrad Rzeszutek Wilk; +Cc: xen-devel, Boris Ostrovsky, David Vrabel
>>> On 21.08.13 at 12:50, Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> wrote:
> Jan Beulich <JBeulich@suse.com> wrote:
>>was anyone of you involved in the recent (rc5->rc6) changes here?
>>I'm asking because this new definition conflicts with _PAGE_PAT,
>>which is unused only for native Linux (and I continue to not really
>>understand their motivation to restrict themselves to just the four
>>most trivial memory types).
>
> I have not. Does it cause regressions?
Afaict it obviously will; luckily I noticed it while merging, so I didn't
get to the point where any problem would be noticed.
Jan
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: Linux/x86's _PAGE_SWP_SOFT_DIRTY definition
2013-08-21 7:42 Linux/x86's _PAGE_SWP_SOFT_DIRTY definition Jan Beulich
2013-08-21 10:50 ` Konrad Rzeszutek Wilk
@ 2013-08-21 11:47 ` David Vrabel
2013-08-21 11:58 ` Konrad Rzeszutek Wilk
1 sibling, 1 reply; 6+ messages in thread
From: David Vrabel @ 2013-08-21 11:47 UTC (permalink / raw)
To: Jan Beulich; +Cc: xen-devel, Boris Ostrovsky
On 21/08/13 08:42, Jan Beulich wrote:
> All,
>
> was anyone of you involved in the recent (rc5->rc6) changes here?
> I'm asking because this new definition conflicts with _PAGE_PAT,
> which is unused only for native Linux (and I continue to not really
> understand their motivation to restrict themselves to just the four
> most trivial memory types).
I was not aware of it and that just looks broken -- not just Xen but it
looks like it wouldn't work with (transparent) huge pages either.
The soft dirty tracking was introduced (in 3.11-rc1) by 0f8975ec4 (mm:
soft-dirty bits for user memory changes tracking) and the problematic
patch adding the conflicting PTE bit is 179ef71cb (mm: save soft-dirty
bits on swapped pages).
David
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: Linux/x86's _PAGE_SWP_SOFT_DIRTY definition
2013-08-21 11:47 ` David Vrabel
@ 2013-08-21 11:58 ` Konrad Rzeszutek Wilk
2013-08-21 12:38 ` David Vrabel
0 siblings, 1 reply; 6+ messages in thread
From: Konrad Rzeszutek Wilk @ 2013-08-21 11:58 UTC (permalink / raw)
To: David Vrabel, Jan Beulich; +Cc: xen-devel, Boris Ostrovsky
David Vrabel <david.vrabel@citrix.com> wrote:
>On 21/08/13 08:42, Jan Beulich wrote:
>> All,
>>
>> was anyone of you involved in the recent (rc5->rc6) changes here?
>> I'm asking because this new definition conflicts with _PAGE_PAT,
>> which is unused only for native Linux (and I continue to not really
>> understand their motivation to restrict themselves to just the four
>> most trivial memory types).
>
>I was not aware of it and that just looks broken -- not just Xen but it
>looks like it wouldn't work with (transparent) huge pages either.
>
>The soft dirty tracking was introduced (in 3.11-rc1) by 0f8975ec4 (mm:
>soft-dirty bits for user memory changes tracking) and the problematic
>patch adding the conflicting PTE bit is 179ef71cb (mm: save soft-dirty
>bits on swapped pages).
>
>David
I am going to be in meetings most of today. David or Jan would you be OK emailing the folks who came up with the patch and the committeer to mention that it causes a regression?
And naturally test it first with a upstream kernel? I presume the regressions is in the form of pages of WB becoming WC and suddenly applications failing oddly?
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: Linux/x86's _PAGE_SWP_SOFT_DIRTY definition
2013-08-21 11:58 ` Konrad Rzeszutek Wilk
@ 2013-08-21 12:38 ` David Vrabel
0 siblings, 0 replies; 6+ messages in thread
From: David Vrabel @ 2013-08-21 12:38 UTC (permalink / raw)
To: Konrad Rzeszutek Wilk; +Cc: xen-devel, Boris Ostrovsky, Jan Beulich
On 21/08/13 12:58, Konrad Rzeszutek Wilk wrote:
> David Vrabel <david.vrabel@citrix.com> wrote:
>> On 21/08/13 08:42, Jan Beulich wrote:
>>> All,
>>>
>>> was anyone of you involved in the recent (rc5->rc6) changes here?
>>> I'm asking because this new definition conflicts with _PAGE_PAT,
>>> which is unused only for native Linux (and I continue to not really
>>> understand their motivation to restrict themselves to just the four
>>> most trivial memory types).
>>
>> I was not aware of it and that just looks broken -- not just Xen but it
>> looks like it wouldn't work with (transparent) huge pages either.
>>
>> The soft dirty tracking was introduced (in 3.11-rc1) by 0f8975ec4 (mm:
>> soft-dirty bits for user memory changes tracking) and the problematic
>> patch adding the conflicting PTE bit is 179ef71cb (mm: save soft-dirty
>> bits on swapped pages).
>>
>> David
>
> I am going to be in meetings most of today. David or Jan would you
> be OK emailing the folks who came up with the patch and the
> committeer to mention that it causes a regression?
>
> And naturally test it first with a upstream kernel? I presume the
> regressions is in the form of pages of WB becoming WC and suddenly
> applications failing oddly?
It's not clear how a test case to show the regression can be reliably
produced in a limited time. The failures from using WC instead of WB
will be pretty subtle.
David
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2013-08-21 12:38 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz follow: Atom feed
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2013-08-21 7:42 Linux/x86's _PAGE_SWP_SOFT_DIRTY definition Jan Beulich
2013-08-21 10:50 ` Konrad Rzeszutek Wilk
2013-08-21 11:45 ` Jan Beulich
2013-08-21 11:47 ` David Vrabel
2013-08-21 11:58 ` Konrad Rzeszutek Wilk
2013-08-21 12:38 ` David Vrabel
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