Thursday, May 8, 2014

Arm builder updates

Debian has recently received a donation of 8 build machines from Marvell. The new machines come with Quad core MV78460 Armada XP CPU's, DDR3 DIMM slot so we can plug in more memory, and speedy sata ports. They replace the well served Marvell MV78200 based builders - ones that have been building debian armel since 2009. We are planning a more detailed announcement, but I'll provide a quick summary:

The speed increase provided by MV78460 can viewed by comparing build times on selected builds since early april:

Qemu build times.

We can now build Qemu in 2h instead of 16h -8x faster than before! Certainly a substantial improvement, so impressive kit from Marvell! But not all packages gain this amount of speedup:

webkitgtk build times.

This example, webkitgtk, builds barely 3x faster. The explanation is found from debian/rules of webkitgkt:

# Parallel builds are unstable, see #714072 and #722520
# ifneq (,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
#   NUMJOBS = $(patsubst parallel=%,%,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
# endif
The old builders are single-core[1], so the regardless of parallel building, you can easily max out the cpu. New builders will use only 1 of 4 cores without parallel build support in debian/rules.

During this buildd cpu usage graph, we see most time only one CPU is consumed. So for fast package build times.. make sure your packages supports parallel building.

For developers, is porter machine with Armada XP. It has schroot's for both armel and armhf. set "DEB_BUILD_OPTIONS=parallel=4" and off you go.

Finally I'd like to thank Thomas Petazzoni, Maen Suleiman, Hector Oron, Steve McIntyre, Adam Conrad and Jon Ward for making the upgrade happen.

Meanwhile, we have unrelated trouble - a bunch of disks have broken within a few days apart. I take the warranty just run out...

[1] only from Linux's point of view. - mv78200 has actually 2 cores, just not SMP or coherent. You could run an RTOS on the other core while you run Linux on the other.

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