Re: DSA concerns for jessie architectures - mips/mipsel

Hi,

>>>>> "Steven" == Steven Chamberlain <[email protected]> writes:

> Hi,
> On 27/09/13 16:23, Graham Whaley wrote:
>> I wish to work with you to remedy some of the listed issues. I've
>> started working with MIPS hardware vendors on availability and
>> pricing of hardware.

> I've wondered if SMP Loongson systems are anywhere to be found:
> http://bbs.lemote.com/viewthread.php?tid=43118

There seem to be Loongson-3A motherboards available, according to:

https://groups.google.com/forum/#!searchin/loongson-dev/loongson$20mini-itx/loongson-dev/twzd5TBz_1k/U6MXpHrEbKAJ

> But I don't see Loongson 3A being an option until at the very least
> jessie kernels support it and are stable with all cores in use.  This
> is just my opinion though and I can't speak for DSA.

I don't see why the kernel being available with Debian should be
important WRT porterboxes.  Stability: didn't know that the 3A have
stability problems.

>> 3) speed. I see 'mips' (but not mipsel in particular) listed as 'too
>> slow'. Sure, Can somebody point me at some indication of the minimum
>> requirement here (not that I'm particularly aiming at the minimum, I
>> just wish to ensure we reach it :-). And, is this just pure
>> single-multi-core/thread-machine speed, or is it a solvable problem
>> by using multiple machines if necessary ?

> On mipsel at least, I recall that libreoffice, openjdk-7, webkit
> seemed to have some difficulty building.  Each source package is built
> on a single machine only, and the current machines are limited to <= 1
> GiB RAM I think so I expect heavy swapping takes place.

I wonder whether it's <= or < 1 GB?  Do the 1 GB machines really have
swapping problems?  More than 2 GB userspace virtual memory per process
aren't (currently) possible on mips32 AFAIR.  If some packages hit that
limit during compilation, we're doomed.

[..]

> I suspect that might refer to this, quoting from OpenBSD[0] :

>> Unfortunately, most of the Loongson 2F-based hardware available at
>> that time suffers from serious problems in the processor's branch
>> prediction logic, causing the system to freeze, for which errata
>> information only exists in the Chinese documentation (chapter 15,
>> missing from the English translation), the only English language
>> information being an e-mail[1] on a toolchain mailing-list.

> [0]: http://www.openbsd.org/loongson.html [1]:
> https://sourceware.org/ml/binutils/2009-11/msg00387.html

AFAIR newer silicon contains fixes for these issues.  My Loongson2f
still seems to have these bugs, as it deadlocks when run with kernels
that don't implement the workarounds.

[..]
> Maybe the existing boxes were not affected, but it was a concern about
> acquiring newer Loongson 2F hardware?

Just a single data point: I'm running a Fuloong 6004 with 1GB RAM
(upgraded) and 750 GB disk (also upgraded) 24/7 and don't experience
more than about 1 deadlock/year.  This system is quite busy although I
assume a build server will take much more load.  The system currently
runs Debian Squeeze with a self-compiled kernel, though the kernel from
backports should perform comparably.

cheers,

David
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