Re: CVS commit: src

[yamt%mwd.biglobe.ne.jp@localhost (YAMAMOTO Takashi)]

> yamt%mwd.biglobe.ne.jp@localhost (YAMAMOTO Takashi) wrote:
> > > Sorry for late reply, let's figure out this. My points was:
> > > - Since MAXCPUS can only be increased, ABI would not be broken;
> > 
> > MAXCPUS can only be increased?  why?
> 
> In time we would like to support more processors, not vice-versa :)
> I guess you do not want to depend on such assumption?

i don't, unless there's a good reason to depend on it.

> > anyway it depends on what do you mean by "ABI would not be broken".
> > old schedctl binaries might not crash.  however they can't handle
> > the increased MAXCPUS properly.
> > <...>
> 
> True, this needs to be fixed...
> 
> > > - Why silent truncation is wrong in this case?
> > 
> > each truncated bits can be either 0 or 1.
> > how can you know which was intended?
> 
> In truncated part would be CPUs whose numbers are >= MAXCPUS. System does not
> support them, so it does not matter. Your concern is error instead silence?

of course, it matters.

- for get, it means showing a wrong bitmap.

- for set, it means saying a success while it actually (partially) failed.

i really don't understand why you don't consider them as bugs.

> > > Are you suggesting CPUSET_SIZE to not depend on MAXCPUS?
> > 
> > i'm suggesting to make it dynamic at least for userland programs.
> > 
> > - syscalls should not truncate bitmaps silently.  they should return
> >   appropriate errors.
> > 
> > - userland should not assume the size of cpuset_t.
> >   there should be a way for userland to query the bitmap size
> >   for "get" syscalls.  (probably like getsockopt)
> 
> OK, we can use syscall or perhaps sysconf(_SC_CPUSET_SIZE) for schedctl(8)
> and suggest to use that in manuals. However, I want to keep the compatibility
> with Linux, they use: sched_setaffinity(pid, sizeof(cpuset_t), &set);

while you can make it compatible, is there any reason to
make our native one (_sched_setaffinity) inherit the limitations?

iirc recent linux has a set of macros to allocate dynamic-sized cpusets.
can you check?

YAMAMOTO Takashi

> 
> -- 
> Best regards,
> Mindaugas
> www.NetBSD.org