Re: Time to bump default VM_SWZONE_SIZE_MAX?


On 08/24/12 07:13, John Baldwin wrote:=0D
> On Friday, August 24, 2012 8:45:43 am Dag-Erling Sm=C3=B8rgrav wrote:=0D
>> John Baldwin <jhb@freebsd.org> writes:=0D
>>> Note that on i386 you can't get more than 4GB of RAM without PAE, and i=
f you=0D
>>> have any modern x86 box with > 4GB of RAM, you are most likely running =
amd64=0D
>>> on it, not i386.  I think i386 would be fine to just keep the limit it =
had.=0D
>>=0D
>> The limit we had was insufficient for 8 GB of swap.=0D
> =0D
> In absolute or practical terms?  Not all swap blocks are fully utilized. =
 At=0D
> Y! the install script we used would compute the maximum theoretical swap =
zone=0D
> needed and then cut it in half, and this worked quite well.  Also, keep i=
n mind,=0D
> this is for i386, not amd64.  At this point i386 is going to be used on s=
maller=0D
> systems (e.g. netbooks, etc.), not servers that have lots of swap.=0D
=0D
I'd like to see i386 bumped slightly, just so that the rule of "allocate sw=
ap=0D
space equal to max(RAM, min(2*RAM, 8 GB))" (which I've seen in lots of plac=
es)=0D
is more likely to be safe.  If I'm understanding things correctly, bumping =
from=0D
32 MB up to 34.5 MB should give us a theoretical 16 GiB or a "safe" 8 GiB l=
imit=0D
on swap usage (2^17 structures which are 276 bytes each on i386).=0D
=0D
But I agree that the real issue was with amd64, not i386.=0D
=0D
-- =0D
Colin Percival=0D
Security Officer Emeritus, FreeBSD | The power to serve=0D
Founder, Tarsnap | www.tarsnap.com | Online backups for the truly paranoid=
=0D

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