Could ARG_MAX be increased?

Ronald Klop ronald-freebsd8 at
Thu Sep 23 12:37:52 PDT 2004

On Fri, 24 Sep 2004 07:27:18 +1200, Juha Saarinen <juhasaarinen at>  

> On Thu, 23 Sep 2004 05:26:20 -0700, David G. Lawrence  
> <dg at> wrote:
>>    I feel compelled to respond since you mentioned me above and since I
>> wrote most of the code involved... :-)
>>    The main issue with increasing the size of ARG_MAX is that it will  
>> result
>> in more kernel virtual memory being reserved for temporary storage of  
>> the
>> args. This used to be a much larger problem when KVM was scarce, but  
>> less
>> of a problem now with 1GB or more of KVM. The args temporary space is
>> allocated out of exec_map (a submap of kernel_map), which is sized to be
>> about 16 * ARG_MAX. The '16' is to allow up to 16 processes to  
>> simultaneously
>> exec until additional execs are blocked waiting for KVM to become
>> available. Anyway, increasing ARG_MAX to 256K (roughly 4MB of KVM)  
>> should
>> be okay on most systems.

Can't it be made dependend on kern.maxusers which is dependend on the max  
amount of memory available? So people with low memory aren't wasting a lot  
of memory?


  Ronald Klop
  Amsterdam, The Netherlands

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