RE: [Xen-devel] increasing the number of guests (NR_DYNIRQS)

[Dan Magenheimer <dan.magenheimer@xxxxxxxxxx>]

IIRC from a preliminary investigation, there are some
memory allocations for which the size is determined by
multiplying by number of dynirqs.  I don't recall whether
this already results in a ("post-boottime") order>0 allocation,
but quadrupling the number might.

Not necessarily a big problem (yet), I'm just being
watchful to see that the fragmentation problem due to
dynamic order>0 allocations doesn't continue to get worse.

> -----Original Message-----
> From: Tim Post [mailto:echo@xxxxxxxxxxxx]
> Sent: Saturday, February 20, 2010 8:44 AM
> To: Keir Fraser
> Cc: Luke S Crawford; xen-devel@xxxxxxxxxxxxxxxxxxx
> Subject: Re: [Xen-devel] increasing the number of guests (NR_DYNIRQS)
> 
> On Sat, 2010-02-20 at 13:41 +0000, Keir Fraser wrote:
> > On 20/02/2010 11:54, "Tim Post" <echo@xxxxxxxxxxxx> wrote:
> >
> > >> #define NR_DYNIRQS           1024
> > >>
> > >> (it defaults to 256)
> > >
> > > I've done the same thing several times without breaking anything.
> What I
> > > could not see is how much more expensive 1024 is than 256. Like
> you, I
> > > had hosts with guests way north of 200 that did very little, so ...
> >
> > Yeah, could even just change to 1024 statically. I don't think it's
> very
> > expensive.
> >
> >  -- Keir
> 
> I think xenstat is capped way below that, so changing this is probably
> going to require some love there too, else xentop might not show all
> guests.
> 
> 
> AFAIK, it was 256, ICBW, I'll check when I get back to my desk. I
> mention it so this doesn't go in without checking.
> 
> Cheers,
> --Tim
> 
> 
> 
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