Ubuntu
multipath-tools package

Default multipath policy is round-robin, shows considerably worse read throughput compared to using service-time

Bug #1634161 reported by bugproxy
14
This bug affects 1 person
Affects Status Importance Assigned to Milestone
Ubuntu on IBM z Systems
Fix Released
Low
Dragan S.
multipath-tools (Ubuntu)
Fix Released
Low
Mathieu Trudel-Lapierre
Ubuntu ubuntu-17.03
Xenial
Won't Fix
Undecided
Unassigned

Bug Description

---Problem Description---
Default multipath policy is round-robin, shows considerably worse read throughput compared to using service-time
Contact Information = Barbara Mundle, <email address hidden>
---uname output---
4.4.0-21-generic
Machine Type = z systems: Type 2964, Model 701 NC9
---Debugger---
A debugger is not configured
---Steps to Reproduce---
 Conducting throughput measurements with both policies shows the difference

Userspace tool common name: multipath-tools
The userspace tool has the following bit modes: 64-bit
Userspace rpm: multipath-tools_0.5.0+git1.656f8865-5ubuntu2.2_s390x.deb
Userspace tool obtained from project website: na

*Additional Instructions for Barbara Mundle, <email address hidden>:
-Attach ltrace and strace of userspace application.

Throughput numbers with FIO for sequential read (in KBPS) with multipath policies service.time/round-robin (varying with number of jobs from 1 - 64):

          service-time round-robin

1 3193030 2917220
2 5248430 5020375
4 8453570 6438140
8 9708690 6444175
16 9712100 6448080
32 9714035 6450905
64 9718355 6461650

bugproxy (bugproxy)
tags: added: architecture-s39064 bugnameltc-147635 severity-high targetmilestone-inin---
Changed in ubuntu:
assignee: nobody → Skipper Bug Screeners (skipper-screen-team)
affects: ubuntu → multipath-tools (Ubuntu)
bugproxy (bugproxy)
tags: added: targetmilestone-inin16041
removed: targetmilestone-inin---
Frank Heimes (fheimes)
Changed in ubuntu-z-systems:
assignee: nobody → Dragan S. (dragan-s)
Revision history for this message
Christian Ehrhardt  (paelzer) wrote :

FYI the minimal bits I checked in the background when we talked about it yesterday.

Done in debian/patches/path_selector.patch

Related Changelog:
  * debian/patches/path_selector.patch: switch the default path selector
    back to round-robin while service-time isn't available to the installer
    multipath-modules.

Likely starts by fully understanding the old dependencies that got to the decision to add that.

Revision history for this message
Dimitri John Ledkov (xnox) wrote :

I wonder if we can check if this is still the case; and if we can build round-robin udeb yet service-time deb.
Furthermore, it might make sense to make sure relevant kernel modules are available as udebs.

Changed in multipath-tools (Ubuntu):
assignee: Skipper Bug Screeners (skipper-screen-team) → Dimitri John Ledkov (xnox)
status: New → Confirmed
milestone: none → later
importance: Undecided → Low
Frank Heimes (fheimes)
Changed in ubuntu-z-systems:
status: New → Confirmed
importance: Undecided → Low
Revision history for this message
Dimitri John Ledkov (xnox) wrote :

dm-service-time.ko is provided in the multipath-modules at least in xenial-release and up.

Revision history for this message
Dimitri John Ledkov (xnox) wrote :

(and round-robin too)

Changed in multipath-tools (Ubuntu):
milestone: later → ubuntu-17.05
Mathieu Trudel-Lapierre (cyphermox)
Changed in multipath-tools (Ubuntu):
assignee: Dimitri John Ledkov (xnox) → Mathieu Trudel-Lapierre (cyphermox)
status: Confirmed → In Progress
milestone: ubuntu-17.05 → ubuntu-17.03
Frank Heimes (fheimes)
Changed in ubuntu-z-systems:
status: Confirmed → In Progress
Revision history for this message
Launchpad Janitor (janitor) wrote :

This bug was fixed in the package multipath-tools - 0.6.4-3ubuntu2

---------------
multipath-tools (0.6.4-3ubuntu2) zesty; urgency=medium

  * debian/initramfs/hooks:
    - Remove old dm-emc module; it hasn't been in kernel since 2.6.27.
    - Add dm-queue-length: users may want to change from the default selector
      and should be able to do so. (LP: #1673350)
  * debian/patches/path_selector.patch, debian/patches/series: remove
    path_selector.patch to get back to the "right" default selector of
    service-time, which has been included in the kernel module packages for
    a while now and has better throughput than round-robin. It's also the
    default upstream. (LP: #1634161)

 -- Mathieu Trudel-Lapierre <email address hidden> Fri, 17 Mar 2017 09:37:36 -0400

Changed in multipath-tools (Ubuntu):
status: In Progress → Fix Released
Revision history for this message
bugproxy (bugproxy) wrote : Comment bridged from LTC Bugzilla

------- Comment From <email address hidden> 2017-03-27 09:20 EDT-------
Verified on zesty (multipath-tools 0.6.4-3ubuntu2), same test, SUT and setup yields the following numbers with service-time now:

1 3189380
2 5274685
4 8448605
8 9700985
16 9712040
32 9714795
64 9717725

Thanks a lot!

Frank Heimes (fheimes)
Changed in ubuntu-z-systems:
status: In Progress → Fix Released
Revision history for this message
bugproxy (bugproxy) wrote :

------- Comment From <email address hidden> 2017-04-11 08:40 EDT-------
IBM Bugzilla status -> closed . Verified

Revision history for this message
Dimitri John Ledkov (xnox) wrote :

cypthermox, were you planning to SRU this into xenial - or should the xenial task be closed?

Changed in multipath-tools (Ubuntu Xenial):
assignee: nobody → Mathieu Trudel-Lapierre (cyphermox)
Mathieu Trudel-Lapierre (cyphermox)
Changed in multipath-tools (Ubuntu Xenial):
assignee: Mathieu Trudel-Lapierre (cyphermox) → nobody
tags: added: rls-x-incoming
Dimitri John Ledkov (xnox)
Changed in multipath-tools (Ubuntu Xenial):
status: New → Won't Fix
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