From: ebiederm@xmission.com (Eric W. Biederman)
To: Thomas Gleixner <tglx@linutronix.de>
Cc: LKML <linux-kernel@vger.kernel.org>,
linux-arch@vger.kernel.org, Linus Torvalds <torvalds@osdl.org>,
Andrew Morton <akpm@linux-foundation.org>,
x86@kernel.org, Peter Zijlstra <peterz@infradead.org>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Paul Mundt <lethal@linux-sh.org>,
Russell King <linux@arm.linux.org.uk>,
David Woodhouse <dwmw2@infradead.org>,
Jesse Barnes <jbarnes@virtuousgeek.org>,
Yinghai Lu <yinghai@kernel.org>,
Grant Likely <grant.likely@secretlab.ca>
Subject: Re: [patch 00/47] Sparse irq rework
Date: Sun, 03 Oct 2010 18:13:15 -0700 [thread overview]
Message-ID: <m11v8692vo.fsf@fess.ebiederm.org> (raw)
In-Reply-To: <alpine.LFD.2.00.1010032034420.14550@localhost6.localdomain6> (Thomas Gleixner's message of "Sun, 3 Oct 2010 21:16:47 +0200 (CEST)")
Thomas Gleixner <tglx@linutronix.de> writes:
>> I don't know that I have a problem with this but I do have a problem
>> with using a bitmap. A lot of the kernels irq usage has been distored
>> because we use a compact array, that we cannot grow over time. Using a
>> bitmap here essentially removes 90% of the point of sparse irq. The
>> ability to remove a hard coded NR_IRQS from the kernel.
>
> Well, lets look at some (un)realistic numbers:
>
> Assume 16k cores and 32 irqs / core. That's 512k interrupts and
> requires a 64k bitmap.
>
> If we hit that limit, then we have some other more serious problems to
> solve.
Possibly.
Fundamentally keeping NR_IRQS anywhere I see as a problem, and it
really disturbs me. Even nr_irqs I see as pretty fishy.
Looking at this objectively I see a bitmap sized to the formula
32*NR_CPUS with NR_CPUS expected to double every 18-24 months.
Which means in a decade our worst case will be 2M not 64k.
Can we please build this with scalable interfaces so we don't have to do
this again in a couple of years, and so we don't have to have little
machines paying the price for big machines, and so that big machines
aren't hamstrung because of data structures built for little machines.
Perhaps this just requires using ida instead of a bitmap.
I really think it is a mistake to use an irq number outside of the
functions in interrupt.h that go to the drivers and the userspace
display functions.
Eric
next prev parent reply other threads:[~2010-10-04 1:13 UTC|newest]
Thread overview: 111+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-09-30 23:14 [patch 00/47] Sparse irq rework Thomas Gleixner
2010-09-30 23:14 ` [patch 01/47] x86: Plug memory leak in sparse irq Thomas Gleixner
2010-09-30 23:14 ` [patch 02/47] x86: Hpet: Fix bogus error check in hpet_assign_irq() Thomas Gleixner
2010-09-30 23:14 ` [patch 03/47] genirq: Provide status modifier Thomas Gleixner
2010-09-30 23:14 ` [patch 04/47] arm: Use irq " Thomas Gleixner
2010-09-30 23:14 ` [patch 05/47] genirq-sanitize-irq-data-accessors.patch Thomas Gleixner
2010-09-30 23:15 ` [patch 06/47] genirq: Distangle kernel/irq/handle.c Thomas Gleixner
2010-09-30 23:15 ` [patch 07/47] genirq: Remove early_init_irq_lock_class() Thomas Gleixner
2010-09-30 23:15 ` [patch 08/47] genirq: Move core only inlines to kernel/irq Thomas Gleixner
2010-09-30 23:15 ` [patch 09/47] isdn: hisax: Replace the bogus access to irq stats Thomas Gleixner
2010-09-30 23:15 ` [patch 10/47] genirq: Remove export of kstat_irqs_cpu Thomas Gleixner
2010-09-30 23:15 ` [patch 11/47] genirq: Provide default irq init flags Thomas Gleixner
2010-09-30 23:15 ` [patch 12/47] arm: Use ARCH_IRQ_INIT_FLAGS Thomas Gleixner
2010-09-30 23:15 ` [patch 13/47] powerpc: " Thomas Gleixner
2010-09-30 23:15 ` [patch 14/47] genirq: Implement a sane sparse_irq allocator Thomas Gleixner
2010-10-01 5:28 ` Yinghai Lu
2010-10-01 20:36 ` Thomas Gleixner
2010-09-30 23:15 ` [patch 15/47] genirq: Prepare proc for real sparse irq support Thomas Gleixner
2010-09-30 23:15 ` [patch 16/47] genirq: Implement sane enumeration Thomas Gleixner
2010-10-03 10:55 ` Grant Likely
2010-09-30 23:15 ` [patch 17/47] genirq-update-kerneldoc.patch Thomas Gleixner
2010-09-30 23:16 ` [patch 18/47] genirq: Use sane sparse allocator Thomas Gleixner
2010-09-30 23:16 ` [patch 19/47] genirq: Query arch for number of early descriptors Thomas Gleixner
2010-09-30 23:16 ` [patch 20/47] x86: Remove useless reinitialization of irq descriptors Thomas Gleixner
2010-10-03 15:21 ` Eric W. Biederman
2010-10-03 18:26 ` Thomas Gleixner
2010-09-30 23:16 ` [patch 21/47] x86: Sanitize apb timer interrupt handling Thomas Gleixner
2010-09-30 23:16 ` [patch 22/47] x86: lguest: Convert to new irq chip functions Thomas Gleixner
2010-09-30 23:16 ` [patch 23/47] x86: Cleanup visws interrupt handling Thomas Gleixner
2010-09-30 23:16 ` [patch 24/47] x86: i8259: Convert to new irq_chip functions Thomas Gleixner
2010-09-30 23:16 ` [patch 25/47] x86: Cleanup io_apic Thomas Gleixner
2010-09-30 23:16 ` [patch 26/47] x86: io_apic: Convert startup to new irq_chip function Thomas Gleixner
2010-09-30 23:16 ` [patch 27/47] x86: ioapic: Convert mask " Thomas Gleixner
2010-09-30 23:16 ` [patch 28/47] x86: ioapic/hpet: Convert to new chip functions Thomas Gleixner
2010-09-30 23:16 ` [patch 29/47] pci: Convert msi to new irq_chip functions Thomas Gleixner
2010-10-11 17:09 ` Jesse Barnes
2010-09-30 23:16 ` [patch 30/47] dmar: Convert to new irq chip functions Thomas Gleixner
2010-09-30 23:17 ` [patch 31/47] ht: Convert to new irq_chip functions Thomas Gleixner
2010-09-30 23:17 ` [patch 32/47] x86: ioapic: Clean up the direct access to irq_desc Thomas Gleixner
2010-09-30 23:17 ` [patch 33/47] pci: Cleanup the irq_desc mess in msi Thomas Gleixner
2010-10-11 17:08 ` Jesse Barnes
2010-09-30 23:17 ` [patch 34/47] x86: ioapic: Convert irq affinity to new chip functions Thomas Gleixner
2010-09-30 23:17 ` [patch 35/47] x86: ioapic: Cleanup some more Thomas Gleixner
2010-09-30 23:17 ` [patch 36/47] x86: ioapic: Cleanup sparse irq code Thomas Gleixner
2010-09-30 23:17 ` [patch 37/47] x86: uv: Clean up the direct access to irq_desc Thomas Gleixner
2010-09-30 23:17 ` [patch 38/47] x86: Use sane enumeration Thomas Gleixner
2010-09-30 23:17 ` [patch 39/47] genirq: Remove arch_init_chip_data() Thomas Gleixner
2010-09-30 23:17 ` [patch 40/47] genirq: Sanitize dynamic irq handling Thomas Gleixner
2010-10-01 5:47 ` Yinghai Lu
2010-09-30 23:18 ` [patch 41/47] arm: davinci: Cleanup irq_desc access Thomas Gleixner
2010-09-30 23:18 ` [patch 42/47] genirq: Remove the now unused sparse irq leftovers Thomas Gleixner
2010-09-30 23:18 ` [patch 43/47] x86: xen: Sanitise sparse_irq handling Thomas Gleixner
2010-09-30 23:18 ` [patch 44/47] sh: Sanitize sparse irq Thomas Gleixner
2010-09-30 23:18 ` [patch 45/47] x86: lguest: Use new irq allocator Thomas Gleixner
2010-09-30 23:18 ` [patch 46/47] powerpc: " Thomas Gleixner
2010-10-01 0:42 ` Benjamin Herrenschmidt
2010-10-01 13:07 ` Thomas Gleixner
2010-10-01 20:46 ` Benjamin Herrenschmidt
2010-10-01 21:11 ` Grant Likely
2010-10-01 21:17 ` Benjamin Herrenschmidt
2010-10-03 16:53 ` Eric W. Biederman
2010-10-03 18:34 ` Thomas Gleixner
2010-10-03 20:04 ` Thomas Gleixner
2010-10-03 22:54 ` Benjamin Herrenschmidt
2010-10-04 0:15 ` Eric W. Biederman
2010-10-04 0:37 ` Benjamin Herrenschmidt
2010-10-04 16:46 ` Grant Likely
2010-09-30 23:18 ` [patch 47/47] genirq: Remove the old sparse irq allocator function Thomas Gleixner
2010-10-01 3:32 ` [patch 00/47] Sparse irq rework Linus Torvalds
2010-10-01 5:54 ` Yinghai Lu
2010-10-01 20:35 ` Thomas Gleixner
2010-10-03 11:23 ` Grant Likely
2010-10-03 11:29 ` Russell King - ARM Linux
2010-10-03 11:57 ` Grant Likely
2010-10-03 13:48 ` Thomas Gleixner
2010-10-05 10:22 ` Thomas Gleixner
2010-10-06 22:45 ` Yinghai Lu
2010-10-06 22:52 ` Thomas Gleixner
2010-10-06 23:37 ` Yinghai Lu
2010-10-07 0:16 ` Yinghai Lu
2010-10-07 4:01 ` Thomas Gleixner
2010-10-07 4:38 ` Yinghai Lu
2010-10-08 21:50 ` Thomas Gleixner
2010-10-08 21:54 ` Thomas Gleixner
2010-10-09 4:26 ` Yinghai Lu
2010-10-09 5:44 ` Yinghai Lu
2010-10-09 6:34 ` Thomas Gleixner
2010-10-09 7:08 ` Yinghai Lu
2010-10-09 12:08 ` Thomas Gleixner
2010-10-10 9:32 ` Thomas Gleixner
2010-10-10 13:30 ` Anca Emanuel
2010-10-11 2:20 ` Yinghai Lu
2010-10-11 3:50 ` Yinghai Lu
2010-10-11 8:16 ` Thomas Gleixner
2010-10-11 11:34 ` Benjamin Herrenschmidt
2010-10-11 16:19 ` Yinghai Lu
2010-10-12 20:23 ` [tip:irq/core] x86: Don't setup ioapic irq for sci twice tip-bot for Yinghai Lu
2010-10-09 6:10 ` [patch 00/47] Sparse irq rework Thomas Gleixner
2010-10-09 7:03 ` Yinghai Lu
2010-10-09 12:12 ` Thomas Gleixner
2010-10-10 2:32 ` Yinghai Lu
2010-10-10 5:11 ` Yinghai Lu
2010-10-10 8:20 ` Thomas Gleixner
2010-10-03 16:41 ` Eric W. Biederman
2010-10-03 19:16 ` Thomas Gleixner
2010-10-03 22:57 ` Benjamin Herrenschmidt
2010-10-04 16:31 ` Grant Likely
2010-10-04 0:49 ` Eric W. Biederman
2010-10-04 8:05 ` Thomas Gleixner
2010-10-04 1:13 ` Eric W. Biederman [this message]
2010-10-04 6:36 ` Ingo Molnar
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