From: Alexander Graf <agraf@suse.de>
To: Liu ping fan <kernelfans@gmail.com>
Cc: kvm-devel <kvm@vger.kernel.org>,
kvm-ppc <kvm-ppc@vger.kernel.org>,
Paul Mackerras <paulus@samba.org>,
"Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>,
linuxppc-dev@lists.ozlabs.org, Alexander Graf <agraf@suse.com>
Subject: Re: [PATCH v2] powernv: kvm: make _PAGE_NUMA take effect
Date: Thu, 10 Apr 2014 12:02:34 +0200 [thread overview]
Message-ID: <53466C3A.5070204@suse.de> (raw)
In-Reply-To: <CAFgQCTtbxRYMBVQL5Fw0254sFAZ_HSzkAfiH0ppNXacRSmxu-w@mail.gmail.com>
On 10.04.14 05:28, Liu ping fan wrote:
> On Mon, Apr 7, 2014 at 4:36 PM, Alexander Graf <agraf@suse.de> wrote:
>> On 07.04.14 09:42, Aneesh Kumar K.V wrote:
>>> Alexander Graf <agraf@suse.com> writes:
>>>
>>>> On 03.04.14 04:36, Liu ping fan wrote:
>>>>> Hi Alex, could you help to pick up this patch? since v3.14 kernel can
>>>>> enable numa fault for powerpc.
>>>> What bad happens without this patch? We map a page even though it was
>>>> declared to get NUMA migrated? What happens next?
>>> Nothing much, we won't be properly accounting the numa access in the
>>> host. What we want to achieve is to convert a guest access of the page to
>>> a host fault so that we can do proper numa access accounting in the
>>> host. This would enable us to migrate the page to the correct numa
>>> node.
>>
>> Ok, so no breakages, just less performance. I wouldn't consider it stable
>> material then :).
>>
> Sorry to reply late, since I am half out of office during this period.
> I am puzzling about you reply. Without this patch, the guest can
> NOT sense the numa changes and ask host to put the pages in right
> place. So the pages which is used by guest will be always misplaced.
> The numa-fault method is inspired by real requirement to improve
> performance, so we should also consider the performance drop of guest.
> Right?
The patch will get into Linux, I just consider a non-working new feature
not a regression that warrants us to CC stable@vger :). After all
performance shouldn't be worse than without the numa migration feature,
correct?
Alex
prev parent reply other threads:[~2014-04-10 10:02 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-01-21 8:15 [PATCH v2] powernv: kvm: make _PAGE_NUMA take effect Liu Ping Fan
2014-01-21 9:42 ` Aneesh Kumar K.V
2014-01-27 9:11 ` Alexander Graf
2014-01-27 10:28 ` Aneesh Kumar K.V
2014-01-27 10:42 ` Alexander Graf
2014-01-27 15:57 ` Aneesh Kumar K.V
2014-01-27 10:41 ` Paul Mackerras
2014-04-03 2:36 ` Liu ping fan
2014-04-03 11:36 ` Alexander Graf
2014-04-03 11:38 ` Alexander Graf
2014-04-03 11:43 ` Alexander Graf
2014-04-07 7:42 ` Aneesh Kumar K.V
2014-04-07 8:36 ` Alexander Graf
2014-04-10 3:28 ` Liu ping fan
2014-04-10 10:02 ` Alexander Graf [this message]
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