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Date: Tue, 29 Jul 2008 15:17:01 -0700
From: Mike Travis <travis@....com>
To: "Eric W. Biederman" <ebiederm@...ssion.com>
CC: Yinghai Lu <yhlu.kernel@...il.com>,
Dhaval Giani <dhaval@...ux.vnet.ibm.com>,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...e.hu>,
lkml <linux-kernel@...r.kernel.org>,
Jack Steiner <steiner@....com>, Alan Mayer <ajm@....com>,
Cliff Wickman <cpw@....com>
Subject: Re: kernel BUG at arch/x86/kernel/io_apic_64.c:357!
Eric W. Biederman wrote:
> "Yinghai Lu" <yhlu.kernel@...il.com> writes:
>
>> On Tue, Jul 29, 2008 at 11:35 AM, Yinghai Lu <yhlu.kernel@...il.com> wrote:
>>> On Tue, Jul 29, 2008 at 9:09 AM, Dhaval Giani <dhaval@...ux.vnet.ibm.com>
>> wrote:
>>>> Hi Ingo, Thomas,
>>>>
>>>> Hit this on 2.6.27-rc1
>>>>
>>>> (The kernel bug is at line 356 (Its 357 as I applied a debug patch to
>>>> print out the irq) (Full dmesg and .config attached)
>>> can you boot with "debug apic=verbose pci=routeirq"?
>> please try attached patch
I didn't follow this from the start but one reason why NR_IRQS based on
NR_CPUS is a bad idea, is the huge (nearly 300Mb) increase in memory usage
(that's mostly wasted.) I believe there's another patch coming real soon
now to make irq allocations dynamic. (I had also hoped to look closer at
your irq abstraction patch you sent a while back. Does that also address
this issue?)
But this would be a show stopper for SGI being able to ship systems if the
distros do not want to waste this much memory and won't set NR_CPUS=4096.
Thanks,
Mike
====== Data (-l 500)
1 - 4k-defconfig
2 - 4k-defconfig-tmp (has this patch)
.1. .2. ..final..
258048 +150994944 151252992 +58514% irq_desc(.data.cacheline_aligned)
231168 +135266304 135497472 +58514% irq_cfg(.data.read_mostly)
3584 +2097152 2100736 +58514% irq_lists(.bss)
2688 +2098048 2100736 +78052% irq_2_pin(.bss)
1792 +1048576 1050368 +58514% irq_timer_state(.bss)
968 +524288 525256 +54161% per_cpu__kstat(.data.percpu)
498248 +292029312 292527560 +58611% Totals
====== Sections (-l 500)
1 - 4k-defconfig
2 - 4k-defconfig-tmp
.1. .2. ..final..
10379571 +292028228 302407799 +2813% Total
1118924 +5242880 6361804 +468% .bss
742016 +150994944 151736960 +20349% .data.cacheline_aligned
274416 +135266304 135540720 +49292% .data.read_mostly
44928 +524288 569216 +1166% .data.percpu
12559855 +584056644 596616499 +4650% Totals
====== Text/Data ()
1 - 4k-defconfig
2 - 4k-defconfig-tmp
.1. .2. ..final..
1118208 +5242880 6361088 +468% BssSize
1232896 +524288 1757184 +42% InitSize
45056 +524288 569344 +1163% PerCPU
1077248 +286261248 287338496 +26573% OtherSize
3473408 +292552704 296026112 +8422% Totals
>
> Ugh. Yuck bleh nasty gag.
>
> Yes please try the YH's patch that should fix the worst of the
> problem.
>
> YH I think you have hit the root cause of the bug with NR_IRQS being
> defined a ridiculously low value on x86_64. At first glance your
> patch looks reasonable, I had to stop and look why it was needed. At
> second glance it looks like it doesn't go far enough.
>
> The commit that unified interrupt vector defines appears substantially
> fumbled. YH your description of why your patch is needed is not
> especially useful.
>
> To be perfectly clear. The maximum number of interrupts we can handle is:
> NR_CPUS*NR_VECTORS. Defining NR_IRQS to a lower value is essentially a
> hack to allows us to use less memory as we seldom push that limit.
>
> Further the only valid definition of NR_IRQ_VECTORS is NR_IRQS
> as we index it by irq. Which really means now that we are unifying
> the code we should simply kill NR_IRQ_VECTORS.
>
> I expect there is a lot more in that mess that can be cleaned up.
> Right now irq_vectors.h reads like nonsense to me. I will see if
> I can find some time soon to look into what we should be doing.
>
> Increasing the size of the next field in the irq_pin_list is a good
> idea. Frankly I think we never use the next field (especially on
> x86_64 and should just remove it) but I have not been brave enough
> to try.
>
> commit 9b7dc567d03d74a1fbae84e88949b6a60d922d82
> Author: Thomas Gleixner <tglx@...utronix.de>
> Date: Fri May 2 20:10:09 2008 +0200
>
> x86: unify interrupt vector defines
>
> The interrupt vector defines are copied 4 times around with minimal
> differences. Move them all into asm-x86/irq_vectors.h
>
> Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
> Signed-off-by: Ingo Molnar <mingo@...e.hu>
>
>> [PATCH] x86: 64bit support more than 256 irq
>>
>> because 64bit allow same vector for different cpu to serve different irq
>>
>> also change next in irq_pin_list from short to next. because for 4096 NR_IRQS
>> is 2^(5+12)+224.
>>
>> need to create that array dynamically later
>>
>> Signed-off-by: Yinghai Lu <yhlu.kernel@...il.com>
>>
>> ---
>> arch/x86/kernel/io_apic_64.c | 3 ++-
>> include/asm-x86/irq_vectors.h | 6 +++++-
>> 2 files changed, 7 insertions(+), 2 deletions(-)
>>
>> Index: linux-2.6/include/asm-x86/irq_vectors.h
>> ===================================================================
>> --- linux-2.6.orig/include/asm-x86/irq_vectors.h
>> +++ linux-2.6/include/asm-x86/irq_vectors.h
>> @@ -113,9 +113,13 @@
>>
>> # if defined(CONFIG_X86_IO_APIC) || defined(CONFIG_PARAVIRT) ||
>> defined(CONFIG_X86_VISWS)/include/asm-x86/irq_vectors.h
>>
>> +#ifdef CONFIG_X86_64
>> +# define NR_IRQS (32 * NR_CPUS + 224)
>> +#else
>> # define NR_IRQS 224
>> +#endif
>>
>> -# if (224 >= 32 * NR_CPUS)
>> +# if (NR_IRQS >= 32 * NR_CPUS)
>> # define NR_IRQ_VECTORS NR_IRQS
>> # else
>> # define NR_IRQ_VECTORS (32 * NR_CPUS)
>> Index: linux-2.6/arch/x86/kernel/io_apic_64.c
>> ===================================================================
>> --- linux-2.6.orig/arch/x86/kernel/io_apic_64.c
>> +++ linux-2.6/arch/x86/kernel/io_apic_64.c
>> @@ -140,7 +140,8 @@ DECLARE_BITMAP(mp_bus_not_pci, MAX_MP_BU
>> */
>>
>> static struct irq_pin_list {
>> - short apic, pin, next;
>> + short apic, pin;
>> + int next;
>> } irq_2_pin[PIN_MAP_SIZE];
>>
>> struct io_apic {
--
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