What is a "sane" setting for maxdsize when running amd64? it seems many normal suggestions do not apply.

N. Harrington drumslayer2 at yahoo.com
Thu Aug 23 16:07:04 PDT 2007

--- JoaoBR <joao at matik.com.br> wrote:
> On Tuesday 21 August 2007 20:54:36 N. Harrington wrote:
> > Hello
> >  I feel stupid, but I am confused about kern.maxdsiz (or datasize via
> > limits command) on FreeBSD amd64.
> >
> >  I have seen many posts and suggestions to raise it to 1G. However it seems
> > this only applies to i386. By default, on servers I have with 4G of
> > physical memory, and 2X that of swap, I am showing a reported datasize
> > limit of 33554432KB. far in excess of even my physical and swap combined! I
> > have seen suggestions from mysql for maxdsize to be set to 1G. Obviously no
> > such problem with amd64?
> on amd64 when maxdsiz not set it stops at 512 limit but soon you set it to 1G  
> it appearently is able to use more  this is not the case on i386 - but I 
> would say don't worry about it
> on i386 your machine could hang at boot when setting maxdsiz higher than 
> installed physical memory but that never happened to me with amd64
> I have some server running squid for caching perfect with 4, 8 and 16G of RAM 
> I set maxdsiz do 3G on machines with 4Gigs of RAM but I do not run anything 
> else so then I adjust cache_mem with maximum_object_size_in_memory to use the 
> most possible amount of memory without doing swap. 
> anyway you set it in boot.loader there is no need to compile something into 
> the kernel
> -- 
> João
 Thanks everyone.

  I tried setting my maxd size to 3.5G on a machine with 4gigs ram. It caused squid to seem to rop
out on occasion. 
 It seems so odd that on i366, maxd size is so small that one likely needs to set it higher to
allow access to more memory. However on amd64, is such a high number that one would need to lower
it to prevent accessing too much memory?  Something really odd about that.

 I also found that I could even double the datasize / maxd size to 2X 33554432kB and it would boot
and run just fine on a machine with 8 gigs of ram. How weird is that! Did amd64 just cause this
setting to add 3 zero's? I can see the legacy documentation for i386 BSD and applications is going
to cause some weirdness and problems if not careful. 

 As for squid, just like Sendmail and Apache, yes there and plenty of "I do it better and I am
newer", alternatives out. But some things stay old favorites for a reason. I will take a look at
Varnish, but it seemed much less user friendly to me that squid and much much less feature laden.
Also, I saw no way to purge individual files from storage. (something I have to have) So it's
always nicer to know how to make things work with what one has or needs to use, rather than just
being told to use something else.

 I have over 30 machines with various configurations of squid in accelerator mode and most seem to
work fine. However I will say they do have a preference for running on (1) Single core cpu and
SCSI hard drives. On an average server with ~300G of disk, I have over 10M objects in storage. As
usual though, I am dealing with a program(squid) that seems to be, Linux first, it happens to also
run on FreeBSD second. Even though it seems many people seem to be using it with FreeBSD. 

 Squid has also been great for me to test/beatup on gjournal (which should be in 6 by now and be
available standard) and zfs.


The Large Print Giveth And The Small Print Taketh Away
 -- Anon

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