rfi-flush: Switch to new linear fallback flush

Bug #1744173 reported by bugproxy on 2018-01-18
8
This bug affects 1 person
Affects Status Importance Assigned to Milestone
The Ubuntu-power-systems project
High
Canonical Kernel Team
linux (Ubuntu)
High
Canonical Kernel Team
Xenial
High
Joseph Salisbury
Artful
High
Joseph Salisbury

Bug Description

[Impact]
Change flush method from "congruence-first with dependencies" to "linear with no dependencies", which increases flush performance by 8x on P8, and
3x on P9. Measured with null syscall loop, which will have the flush area in the L2 cache.

The flush also becomes simpler and more adaptable to different cache
geometries.

[Test Case]
TBD.

[Regression Potential]
The risk is deemed low since the changes are confined to POWER only and the provided test kernels have been tested by IBM.

bugproxy (bugproxy) on 2018-01-18
tags: added: architecture-ppc64le bugnameltc-163715 severity-medium targetmilestone-inin1710
Changed in ubuntu:
assignee: nobody → Ubuntu on IBM Power Systems Bug Triage (ubuntu-power-triage)

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[This is an automated message. I apologize if it reached you inappropriately; please just reply to this message indicating so.]

tags: added: bot-comment

------- Comment (attachment only) From <email address hidden> 2018-01-19 07:39 EDT-------

Changed in ubuntu-power-systems:
importance: Undecided → Medium
assignee: nobody → Canonical Kernel Team (canonical-kernel-team)
tags: added: triage-g
affects: ubuntu → linux (Ubuntu)

------- Comment From <email address hidden> 2018-01-19 09:33 EDT-------
Canonical, please target this one for Xenial GA (4.4) also, please.
This also affects Xenial and I am attaching the backport of the fix for Xenial

------- Comment (attachment only) From <email address hidden> 2018-01-19 09:34 EDT-------

Changed in ubuntu-power-systems:
status: New → Triaged
Manoj Iyer (manjo) on 2018-01-22
Changed in linux (Ubuntu):
assignee: Ubuntu on IBM Power Systems Bug Triage (ubuntu-power-triage) → Canonical Kernel Team (canonical-kernel-team)
Changed in linux (Ubuntu Xenial):
assignee: nobody → Canonical Kernel Team (canonical-kernel-team)
Changed in linux (Ubuntu):
importance: Undecided → Medium
Changed in linux (Ubuntu Xenial):
importance: Undecided → Medium
tags: added: kernel-da-key
Changed in linux (Ubuntu):
status: New → Triaged
Changed in linux (Ubuntu Xenial):
status: New → Triaged
Manoj Iyer (manjo) on 2018-02-12
tags: added: triage-a
removed: triage-g
Andrew Cloke (andrew-cloke) wrote :

Hi Breno, this bug is currently marked with a "medium" priority. Should that prioritisation be reviewed? Thanks, Andy.

Breno Leitão (breno-leitao) wrote :

Yes, Andy. This is part of the Meltdown patchset. It is very important to have it integrated, as, it increase the flush performance in 8x on a POWER8.

Changed in ubuntu-power-systems:
importance: Medium → High
Manoj Iyer (manjo) on 2018-03-05
Changed in linux (Ubuntu Xenial):
importance: Medium → High
Changed in linux (Ubuntu):
importance: Medium → High
Changed in linux (Ubuntu Artful):
status: New → Triaged
importance: Undecided → High
assignee: nobody → Canonical Kernel Team (canonical-kernel-team)

------- Comment (attachment only) From <email address hidden> 2018-01-19 07:39 EDT-------

I built Xenial and Artful test kernels with the patch sets provided in comments #2 and #4. The test kernels can be downloaded from:

http://kernel.ubuntu.com/~jsalisbury/lp1744173

Can you test this kernel and see if it resolves this bug?

Note, to test this kernel, you need to install both the linux-image and linux-image-extra .deb packages.

Thanks in advance!

Manoj Iyer (manjo) on 2018-04-05
Changed in linux (Ubuntu Artful):
status: Triaged → Incomplete
Breno Leitão (breno-leitao) wrote :

hi Joseph,

I tested on both versions and the kernel solves the problem:

== Xenial ==
# uname -a
Linux 1604 4.4.0-116-generic #140~lp1744174 SMP Tue Mar 6 14:15:54 UTC 2018 ppc64le ppc64le ppc64le GNU/Linux

== Artful ==
# uname -a
Linux 1710 4.13.0-36-generic #40~lp1744173 SMP Tue Mar 6 14:17:17 UTC 2018 ppc64le ppc64le ppc64le GNU/Linux

The patches can make the official tree in my opinion.

PS: You look the kernel version, it has the extesion ~lpXXXXXX, one refers to lp1744173 and the other one to lp1744174, but I understand it was a typo, and both refers to the same fix (lp1744173), right?

Thanks!

Joseph Salisbury (jsalisbury) wrote :

You are correct. The xenial kernel name had a type in it. Sorry about that.

Changed in linux (Ubuntu Artful):
status: Incomplete → Triaged
status: Triaged → In Progress
Changed in linux (Ubuntu Xenial):
status: Triaged → In Progress
Changed in linux (Ubuntu):
status: Triaged → In Progress
Changed in linux (Ubuntu Xenial):
assignee: Canonical Kernel Team (canonical-kernel-team) → Joseph Salisbury (jsalisbury)
Changed in linux (Ubuntu Artful):
assignee: Canonical Kernel Team (canonical-kernel-team) → Joseph Salisbury (jsalisbury)
Changed in ubuntu-power-systems:
status: Triaged → In Progress
Breno Leitão (breno-leitao) wrote :

Hello Joseph,

Any update on this bug?

Juerg Haefliger (juergh) wrote :

Hi Breno,

Sorry for the late reply. Regarding Xenial, we updated the kernel to a later upstream stable version since you posted the patches. 4.4.0-123.147 from -proposed should be in sync with 4.4.128 now and your patches don't apply cleanly any longer. When updating to 4.4.117 we reverted a bunch of SAUCE rfi-flush patches and replaced them with the upstream versions. Is there a possibility that your patches are no longer required with those updates?

Thanks
...Juerg

Juerg Haefliger (juergh) on 2018-05-08
summary: - artful: rfi-flush: Switch to new linear fallback flush
+ rfi-flush: Switch to new linear fallback flush
Juerg Haefliger (juergh) on 2018-05-08
description: updated
Breno Leitão (breno-leitao) wrote :

Hi Juerg,

> When updating to 4.4.117 we reverted a bunch of SAUCE rfi-flush patches and replaced them with the
> upstream versions. Is there a possibility that your patches are no longer required with those updates?

None of these patches seems to be integrated int 4.4.0-124. So, we will need to backport them again. I will be working to get this done.

What about artful (kernel 4.13). Are the patches still applying?

------- Comment on attachment From <email address hidden> 2018-05-24 21:22 EDT-------

I have updated the patchset for Artful with master-next today and a single test of stress-ng.

Juerg Haefliger (juergh) on 2018-05-25
description: updated

------- Comment on attachment From <email address hidden> 2018-05-25 16:20 EDT-------

The previous update on xenial branch for stf barrier brought some base patches for rfi flush, set up to a minimal patchset at beginning with 16 and now 4 patches.

tags: added: triage-g
removed: triage-a
Juerg Haefliger (juergh) wrote :

For the latest xenial patchset: What's the purpose of patches 0001 & 0004??

------- Comment From <email address hidden> 2018-05-29 10:41 EDT-------
@juergh

I believe all of them in the xenial_wav2_patchet.tar.gz.

@brenohl

Any concern?

bugproxy (bugproxy) wrote :

------- Comment From <email address hidden> 2018-05-29 10:52 EDT-------
hi there,

I understand those two patches helped on the clean cherry pick of the other two. We might not need it if we decide to backport the other patches other than cleanly cherry pick .

Juerg Haefliger (juergh) wrote :

Thanks for the clarification, @brenohl. I decided to drop the two and adjust the patch that collided. See https://lists.ubuntu.com/archives/kernel-team/2018-May/092834.html.

Juerg Haefliger (juergh) on 2018-06-07
Changed in linux (Ubuntu Xenial):
status: In Progress → Fix Committed
Changed in linux (Ubuntu Artful):
status: In Progress → Fix Committed
Manoj Iyer (manjo) on 2018-06-11
Changed in ubuntu-power-systems:
status: In Progress → Fix Committed
Brad Figg (brad-figg) wrote :

This bug is awaiting verification that the kernel in -proposed solves the problem. Please test the kernel and update this bug with the results. If the problem is solved, change the tag 'verification-needed-artful' to 'verification-done-artful'. If the problem still exists, change the tag 'verification-needed-artful' to 'verification-failed-artful'.

If verification is not done by 5 working days from today, this fix will be dropped from the source code, and this bug will be closed.

See https://wiki.ubuntu.com/Testing/EnableProposed for documentation how to enable and use -proposed. Thank you!

tags: added: verification-needed-artful
Brad Figg (brad-figg) wrote :

This bug is awaiting verification that the kernel in -proposed solves the problem. Please test the kernel and update this bug with the results. If the problem is solved, change the tag 'verification-needed-xenial' to 'verification-done-xenial'. If the problem still exists, change the tag 'verification-needed-xenial' to 'verification-failed-xenial'.

If verification is not done by 5 working days from today, this fix will be dropped from the source code, and this bug will be closed.

See https://wiki.ubuntu.com/Testing/EnableProposed for documentation how to enable and use -proposed. Thank you!

tags: added: verification-needed-xenial
Changed in linux (Ubuntu):
status: In Progress → Fix Committed

Hello IBM,

Could you please verify the fix(es) with the Xenial and Artful kernels currently in -proposed?

Thank you.

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