MAXFILES in subr_param.c

[Ivan Voras]

Dag-Erling Smørgrav wrote:
> Ivan Voras <ivoras at freebsd.org> writes:
>> I'm looking at kern/subr_param.c:
>>
>>  72 #ifndef MAXFILES
>>  73 #define MAXFILES (maxproc * 2)
>>  74 #endif
>>
>> Shouldn't this be at least maxproc*3, for stdin,out,err for every proc?
> 
> Even maxproc * 3 won't be enough, unless none of your processes actually
> do anything. 
> It's just an arbitrary value, based on the assumption that
> you will never have maxproc concurrent processes anyway.

Ok.

> 
>> Also, it looks like MAXFILES is used only once, and in a bit funny way:
>>
>> 238         maxfiles = MAXFILES;
>> 239         TUNABLE_INT_FETCH("kern.maxfiles", &maxfiles);
>> 240         maxprocperuid = (maxproc * 9) / 10;
>> 241         maxfilesperproc = (maxfiles * 9) / 10;
> 
> What's funny about it?

MAXFILES is a macro used only once, where it resolves to (maxproc*2).
It's not technically incorrect, but it looks like it adds noise.

>> Historical reasons?
> 
> To a certain degree, yes; MAXFILES used to be a static limit which you
> could only change in your kernel config.  It is now a loader tunable
> (though you can still change the default in your kernel config), so the
> MAXFILES macro was replaced with a maxfiles variable wherever it is
> used, and the former is now only used to initialize the latter.

Ok.

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