[M3devel] user threads

[Olaf Wagner]

Quoting Tony Hosking <hosking at cs.purdue.edu>:

> On 30 Apr 2009, at 04:46, Mika Nystrom wrote:
>
>> But what Jay has pointed out is that what I labeled as "kernel
>> threads" in the attached table aren't kernel threads at all but
>> libc_r threads, which provide the same facilities (as far as I know)
>> as M3's "user threads".  In this case M3's user threads are simply
>> superior to what the system provides.  Much superior.
>
> Ah, understood.

Threading on FreeBSD has been a sad topic for many years.
Actually I think I was among the first who ever got a threading
library working on FreeBSD (was it still 1.5 or some 2.x?) for
the company I worked for in the 1990s (Point-of-Sale applications).
Unfortunately, that system was never sold nor could it be released
as open source. There was no official FreeBSD thread support then.

Later official solutions were always wanting in functionality or
performance. I think in FreeBSD 6 there are not less than three
different implementations, all of which have some advantages and
disadvantages. But M3 threads were always much faster than any
of the FreeBSD libraries. I think the situation may have got better
in FreeBSD 7, but I haven't really tried that.

>> I think if possible "M3 user threads" should definitely be the
>> default on FreeBSD4 and earlier, rather than "system user threads".
>
> Fair enough.  Old thread libraries were pretty substandard.

Indeed. And that's exactly why I'm still a `fan' of the M3 threads
and think they should not be abandoned and be available for certain
applications.

Sorry, I couldn't resist to comment on this again :-)

I'll return to serious work now and will not feed the M3 mail
flood (which is really a good thing as it shows the interest and
activity) any more,

Olaf
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