Re: choice of i386 vs amd64 guest

2016-10-18 Thread Nicolas Gilles 
On Tue, Oct 18, 2016 at 10:41 AM, Victor Sudakov  wrote:
> Paul Vixie wrote:
>>
>> >
>> > When I must run several FreeBSD guests in bhyve, should I prefer i386
>> > or amd64 guests provided a guest will never need more than 2-3 GB of
>> > RAM?
>>
>> if you're running bind9, the sizeof(void *) will dominate your heap
>> size, and a 32-bit guest will be better overall, given that you don't
>> need the larger addressing size.
>
> Those guests will be running web servers mostly.
>
>>
>> for everything else, the larger register set on amd64 will matter more,
>> and you should probably use a 64-bit guest.
>
> There is an opinion that 64-bit systems use up more resources than
> 32-bit ones for the same tasks, it that not true?
>

Yes, in fact, it's not an opinion, it's a fact, the "issue" is that in
amd64 pointers
are 64bits wide, so take up twice as much space in memory as they would
on 32-bit mode. So if your workload/datastructures are mainly manipulating
lots of pointers you will see higher memory usage. On the other hand 64bit
has larger register set and guaranteed presence of SSE2 instructions
making it more suitable where more computations are taking place.

> --
> Victor Sudakov,  VAS4-RIPE, VAS47-RIPN
> sip:suda...@sibptus.tomsk.ru
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Re: choice of i386 vs amd64 guest

2016-10-18 Thread Victor Sudakov 
Paul Vixie wrote:
> 
> > 
> > When I must run several FreeBSD guests in bhyve, should I prefer i386
> > or amd64 guests provided a guest will never need more than 2-3 GB of
> > RAM? 
> 
> if you're running bind9, the sizeof(void *) will dominate your heap
> size, and a 32-bit guest will be better overall, given that you don't
> need the larger addressing size.

Those guests will be running web servers mostly.

> 
> for everything else, the larger register set on amd64 will matter more,
> and you should probably use a 64-bit guest.

There is an opinion that 64-bit systems use up more resources than
32-bit ones for the same tasks, it that not true?

-- 
Victor Sudakov,  VAS4-RIPE, VAS47-RIPN
sip:suda...@sibptus.tomsk.ru
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Re: choice of i386 vs amd64 guest

2016-10-17 Thread Paul Vixie 


Victor Sudakov wrote:
> Colleagues,
> 
> When I must run several FreeBSD guests in bhyve, should I prefer i386
> or amd64 guests provided a guest will never need more than 2-3 GB of
> RAM? 

if you're running bind9, the sizeof(void *) will dominate your heap
size, and a 32-bit guest will be better overall, given that you don't
need the larger addressing size.

for everything else, the larger register set on amd64 will matter more,
and you should probably use a 64-bit guest.

-- 
P Vixie

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