From: Michael Neuling <mikey@neuling.org>
To: michael@ellerman.id.au
Cc: linuxppc-dev@ozlabs.org
Subject: Re: [RFC/PATCH] powerpc: Dynamically allocate pacas
Date: Wed, 27 Jan 2010 13:40:44 +1030 [thread overview]
Message-ID: <16692.1264561844@neuling.org> (raw)
In-Reply-To: <1264561612.14310.15.camel@concordia>
> On Fri, 2010-01-22 at 16:19 +1300, Michael Neuling wrote:
> >=20
> > In message <39fb8f1aeab9940b86c940b9a5f8e6bd41ec316c.1263368253.git.micha=
> el@ell
> > erman.id.au> you wrote:
> > > On 64-bit kernels we currently have a 512 byte struct paca_struct for
> > > each cpu (usually just called "the paca"). Currently they are staticall=
> y
> > > allocated, which means a kernel built for a large number of cpus will
> > > waste a lot of space if it's booted on a machine with few cpus.
> > >=20
> > > We can avoid that by only allocating the number of pacas we need at
> > > boot. However this is complicated by the fact that we need to access
> > > the paca before we know how many cpus there are in the system.
> > >=20
> > > The solution is to dynamically allocate enough space for NR_CPUS pacas,
> > > but then later in boot when we know how many cpus we have, we free any
> > > unused pacas.
> > >=20
> > > Lightly booted on Legacy iSeries & pSeries LPAR.
> >=20
> > This is broken on 32bit CPUs. Dies at compile time with
> > mpc86xx_defconfig. No paca on 32bit :-(
>
> Bah, who really uses 32-bit anyway ..
Hehe, that's coming from the guy who tested it on iSeries... :-P
Mikey
prev parent reply other threads:[~2010-01-27 3:10 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-01-13 7:37 [RFC/PATCH] powerpc: Dynamically allocate pacas Michael Ellerman
2010-01-14 0:26 ` Michael Neuling
2010-01-14 0:30 ` Michael Ellerman
2010-01-22 3:19 ` Michael Neuling
2010-01-27 3:06 ` Michael Ellerman
2010-01-27 3:10 ` Michael Neuling [this message]
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