Linaro Linux

Performance regression between 2.6.35 and 3.0

Bug #831683 reported by Michael Hope
10
This bug affects 1 person
Affects Status Importance Assigned to Milestone
Linaro Linux
Triaged
Low
Amit Kucheria

Bug Description

Using the current git head, CPU bound tests like CoreMark run at 78 % of the speed of a 2.6.35 kernel.

The .config, branches and refs of the 2.6.35 kernel are here:
 http://bazaar.launchpad.net/~michaelh1/+junk/hardware/files/head:/ursa/r2/

which is basically kernel-ubuntu from dev.omapzoom.org.

This is with linux-linaro-3.0 v3.0.3-751-gdbf7603. The .config of the 3.0 kernel is attached. It's from hwpack_linaro-panda_20110821-0 with the ethernet driver and EXT4 linked in.

This is on an A2 PandaBoard running Natty. The board is perfectly stable under 2.6.35.

Revision history for this message
Michael Hope (michaelh1) wrote :
Revision history for this message
Michael Hope (michaelh1) wrote :

/proc/cpuinfo reads ~1500 BogoMips vs ~2000 on the earlier kernel as well.

Revision history for this message
Michael Hope (michaelh1) wrote :

Adding 'nosmp' to the kernel command line has no effect on the CoreMark score.

Revision history for this message
Rajendra Nayak (rnayak) wrote :

The difference in BogoMips, I guess is due to the different bootlaoders used with the .35 kernel and the 3.0 one.
I see in the Bootlogs attached that SPL is used with the 3.0 kernel, and FWIK SPL configures the MPU on OMAP4 to
be at 792 Mhz (100% OPP) and the x-loader that would have been used with the .35 kernel was instead configuring the
MPU at overdrive (1Ghz) and so the performance drop is probably expected.

Linus Walleij (triad)
Changed in linux-linaro:
assignee: nobody → Amit Kucheria (amitk)
status: New → Triaged
Jakub Pavelek (jakub-pavelek)
Changed in linux-linaro:
importance: Undecided → Low
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