From: Milton Miller <miltonm@bga•com>
To: michael@ellerman•id.au
Cc: ppcdev <linuxppc-dev@ozlabs•org>,
Paul Mackerras <paulus@samba•org>,
Anton Blanchard <anton@samba•org>,
fastboot@lists•osdl.org
Subject: Re: [PATCH] Fix interrupt distribution in ppc970
Date: Tue, 10 Apr 2007 11:59:28 -0500 [thread overview]
Message-ID: <eeb3b19029c753682f476e97dcfaa820@bga.com> (raw)
In-Reply-To: <1176188763.9836.16.camel@concordia.ozlabs.ibm.com>
On Apr 10, 2007, at 2:06 AM, Michael Ellerman wrote:
> On Mon, 2007-04-09 at 14:27 +0530, Mohan Kumar M wrote:
>> On Wed, Mar 07, 2007 at 11:52:32AM +0100, Michael Ellerman wrote:
>>> There's already maxcpus in init/main.c, that would probably be
>>> better,
>>> though still ugly.
>>>
>> Based on Mike's suggestions, I modified the patch. The attached patch
>> refers max_cpus variable to check whether the kernel is booted with
>> maxcpus=1 parameter and if maxcpus=1 is specified the patch assigns
>> only
>> the current boot cpu to be the default distribution server.
>
> So the core of the problem is that if we haven't onlined all cpus then
> we can't use the default_distrib_server value given to us by firmware,
> because some of the cpus in that queue won't be online.
>
> We can detect this situation by comparing the number of cpus that are
> online vs the number that are present (not possible). This might even
> work if you boot with maxcpus=1 and then hotplug the rest in.
>
> How about this:
>
> Index: powerpc/arch/powerpc/platforms/pseries/xics.c
> ===================================================================
> --- powerpc.orig/arch/powerpc/platforms/pseries/xics.c
> +++ powerpc/arch/powerpc/platforms/pseries/xics.c
> @@ -167,7 +167,10 @@ static int get_irq_server(unsigned int v
> return default_server;
>
> if (cpus_equal(cpumask, CPU_MASK_ALL)) {
> - server = default_distrib_server;
> + if (num_online_cpus() == num_present_cpus())
> + server = default_distrib_server;
> + else
> + server = default_server;
> } else {
> cpus_and(tmp, cpu_online_map, cpumask);
This means we are doing population counts of two masks, when we really
just care that they are the same. How about using
cpus_equal(cpu_online_mask, cpu_present_mask)?
>
> @@ -415,7 +418,10 @@ static void xics_set_affinity(unsigned i
>
> /* For the moment only implement delivery to all cpus or one cpu */
> if (cpus_equal(cpumask, CPU_MASK_ALL)) {
> - newmask = default_distrib_server;
> + if (num_online_cpus() == num_present_cpus())
> + newmask = default_distrib_server;
> + else
> + newmask = default_server;
> } else {
> cpus_and(tmp, cpu_online_map, cpumask);
> if (cpus_empty(tmp))
This shows how close these two functions are. The difference is
what happens when cpus_empty is true -- we default in one and
ignore in the other.
How about adding another arg to get_server, that says to fail
or default for the empty case, with failure being -1?
I'll try to code this up, but it might be a day or two until i get
the time.
milton
next prev parent reply other threads:[~2007-04-10 16:59 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-12-08 4:55 [PATCH] Fix interrupt distribution in ppc970 Mohan Kumar M
2006-12-18 4:37 ` Paul Mackerras
2006-12-18 5:14 ` Mohan Kumar M
2006-12-18 10:57 ` Mohan Kumar M
2007-01-02 11:42 ` [Fastboot] " Mohan Kumar M
2007-01-02 15:07 ` Doug Maxey
2007-03-06 13:57 ` Mohan Kumar M
2007-03-06 14:16 ` Michael Ellerman
2007-03-06 16:55 ` Mohan Kumar M
2007-03-06 17:37 ` Michael Ellerman
2007-03-07 4:53 ` Mohan Kumar M
2007-03-07 10:52 ` Michael Ellerman
2007-04-09 8:57 ` Mohan Kumar M
2007-04-10 7:06 ` Michael Ellerman
2007-04-10 12:54 ` Mohan Kumar M
2007-04-10 16:59 ` Milton Miller [this message]
2007-04-11 1:16 ` Michael Ellerman
2007-04-19 11:52 ` Mohan Kumar M
2007-04-20 5:45 ` Milton Miller
2007-04-26 9:24 ` Mohan Kumar M
2007-04-26 14:42 ` Milton Miller
2007-05-03 14:47 ` Mohan Kumar M
2007-05-06 6:52 ` Milton Miller
2007-06-04 10:54 ` Mohan Kumar M
2007-06-06 9:43 ` Milton Miller
2007-06-06 11:31 ` Mohan Kumar M
2007-06-11 1:58 ` Milton Miller
2007-06-11 18:07 ` Mohan Kumar M
2007-06-12 14:51 ` Mohan Kumar M
2007-06-15 16:35 ` Milton Miller
2007-03-07 6:06 ` [Fastboot] " Vivek Goyal
2007-03-07 10:46 ` Michael Ellerman
2007-03-06 22:05 ` Nathan Lynch
2007-03-07 5:01 ` Mohan Kumar M
2007-03-07 8:52 ` Benjamin Herrenschmidt
2007-03-07 9:10 ` Mohan Kumar M
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