From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Michael Neuling To: michael@ellerman.id.au Subject: Re: [PATCH] powerpc: Dynamically allocate pacas In-reply-to: <1264632445.6352.6.camel@concordia> References: <4389.1264575576@neuling.org> <1264632445.6352.6.camel@concordia> Date: Thu, 28 Jan 2010 09:57:33 +1030 Message-ID: <8748.1264634853@neuling.org> Cc: linuxppc-dev@ozlabs.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , > > > 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 > > > Signed-off-by: Michael Ellerman > >=20 > > > >=20 > > > --- a/arch/powerpc/kernel/setup-common.c > > > +++ b/arch/powerpc/kernel/setup-common.c > > > @@ -493,6 +493,8 @@ void __init smp_setup_cpu_maps(void) > > > * here will have to be reworked > > > */ > > > cpu_init_thread_core_maps(nthreads); > > > + > > > + free_unused_pacas(); > >=20 > > This is still barfing for me on 32bit. > > Darn, what config? I built at least one :) I think I used mpc86xx_defconfig. > > Putting an #include at the top of setup-common.c fixes it. > > Gah, I saw it was coming via somewhere else but decided not to add it, > wrong decision :) IMHO, if it's used we should put it in. Otherwise some other random include file will remove it and break us. Mikey