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authorNatalie Protasevich <Natalie.Protasevich@unisys.com>2005-06-23 00:08:41 -0700
committerLinus Torvalds <torvalds@ppc970.osdl.org>2005-06-23 09:45:13 -0700
commit701067c4661ebcdc155cc8f696acb24c016c058b (patch)
treec3566fe8dd278707273480c2ecc653bd6d291705
parent32ecd42b6f94d3ee320a22827b46bd19ccf924e5 (diff)
downloadblackbird-op-linux-701067c4661ebcdc155cc8f696acb24c016c058b.tar.gz
blackbird-op-linux-701067c4661ebcdc155cc8f696acb24c016c058b.zip
[PATCH] x86_64: avoid wasting IRQs
I suggest to change the way IRQs are handed out to PCI devices. Currently, each I/O APIC pin gets associated with an IRQ, no matter if the pin is used or not. It is expected that each pin can potentually be engaged by a device inserted into the corresponding PCI slot. However, this imposes severe limitation on systems that have designs that employ many I/O APICs, only utilizing couple lines of each, such as P64H2 chipset. It is used in ES7000, and currently, there is no way to boot the system with more that 9 I/O APICs. The simple change below allows to boot a system with say 64 (or more) I/O APICs, each providing 1 slot, which otherwise impossible because of the IRQ gaps created for unused lines on each I/O APIC. It does not resolve the problem with number of devices that exceeds number of possible IRQs, but eases up a tension for IRQs on any large system with potentually large number of devices. I only implemented this for the ACPI boot, since if the system is this big and using newer chipsets it is probably (better be!) an ACPI based system :). The change is completely "mechanical" and does not alter any internal structures or interrupt model/implementation. The patch works for both i386 and x86_64 archs. It works with MSIs just fine, and should not intervene with implementations like shared vectors, when they get worked out and incorporated. To illustrate, below is the interrupt distribution for 2-cell ES7000 with 20 I/O APICs, and an Ethernet card in the last slot, which should be eth1 and which was not configured because its IRQ exceeded allowable number (it actially turned out huge - 480!): zorro-tb2:~ # cat /proc/interrupts CPU0 CPU1 CPU2 CPU3 CPU4 CPU5 CPU6 CPU7 0: 65716 30012 30007 30002 30009 30010 30010 30010 IO-APIC-edge timer 4: 373 0 725 280 0 0 0 0 IO-APIC-edge serial 8: 0 0 0 0 0 0 0 0 IO-APIC-edge rtc 9: 0 0 0 0 0 0 0 0 IO-APIC-level acpi 14: 39 3 0 0 0 0 0 0 IO-APIC-edge ide0 16: 108 13 0 0 0 0 0 0 IO-APIC-level uhci_hcd:usb1 18: 0 0 0 0 0 0 0 0 IO-APIC-level uhci_hcd:usb3 19: 15 0 0 0 0 0 0 0 IO-APIC-level uhci_hcd:usb2 23: 3 0 0 0 0 0 0 0 IO-APIC-level ehci_hcd:usb4 96: 4240 397 18 0 0 0 0 0 IO-APIC-level aic7xxx 97: 15 0 0 0 0 0 0 0 IO-APIC-level aic7xxx 192: 847 0 0 0 0 0 0 0 IO-APIC-level eth0 NMI: 0 0 0 0 0 0 0 0 LOC: 273423 274528 272829 274228 274092 273761 273827 273694 ERR: 7 MIS: 0 Even though the system doesn't have that many devices, some don't get enabled only because of IRQ numbering model. This is the IRQ picture after the patch was applied: zorro-tb2:~ # cat /proc/interrupts CPU0 CPU1 CPU2 CPU3 CPU4 CPU5 CPU6 CPU7 0: 44169 10004 10004 10001 10004 10003 10004 6135 IO-APIC-edge timer 4: 345 0 0 0 0 244 0 0 IO-APIC-edge serial 8: 0 0 0 0 0 0 0 0 IO-APIC-edge rtc 9: 0 0 0 0 0 0 0 0 IO-APIC-level acpi 14: 39 0 3 0 0 0 0 0 IO-APIC-edge ide0 17: 4425 0 9 0 0 0 0 0 IO-APIC-level aic7xxx 18: 15 0 0 0 0 0 0 0 IO-APIC-level aic7xxx, uhci_hcd:usb3 21: 231 0 0 0 0 0 0 0 IO-APIC-level uhci_hcd:usb1 22: 26 0 0 0 0 0 0 0 IO-APIC-level uhci_hcd:usb2 23: 3 0 0 0 0 0 0 0 IO-APIC-level ehci_hcd:usb4 24: 348 0 0 0 0 0 0 0 IO-APIC-level eth0 25: 6 192 0 0 0 0 0 0 IO-APIC-level eth1 NMI: 0 0 0 0 0 0 0 0 LOC: 107981 107636 108899 108698 108489 108326 108331 108254 ERR: 7 MIS: 0 Not only we see the card in the last I/O APIC, but we are not even close to using up available IRQs, since we didn't waste any. Signed-off-by: Natalie Protasevich <Natalie.Protasevich@unisys.com> Acked-by: Andi Kleen <ak@suse.de> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat
-rw-r--r--arch/x86_64/kernel/mpparse.c21
1 files changed, 20 insertions, 1 deletions
diff --git a/arch/x86_64/kernel/mpparse.c b/arch/x86_64/kernel/mpparse.c
index ed6a5588146d..9c5aa2a790c7 100644
--- a/arch/x86_64/kernel/mpparse.c
+++ b/arch/x86_64/kernel/mpparse.c
@@ -906,11 +906,20 @@ void __init mp_config_acpi_legacy_irqs (void)
return;
}
+#define MAX_GSI_NUM 4096
+
int mp_register_gsi(u32 gsi, int edge_level, int active_high_low)
{
int ioapic = -1;
int ioapic_pin = 0;
int idx, bit = 0;
+ static int pci_irq = 16;
+ /*
+ * Mapping between Global System Interrupts, which
+ * represent all possible interrupts, to the IRQs
+ * assigned to actual devices.
+ */
+ static int gsi_to_irq[MAX_GSI_NUM];
if (acpi_irq_model != ACPI_IRQ_MODEL_IOAPIC)
return gsi;
@@ -945,11 +954,21 @@ int mp_register_gsi(u32 gsi, int edge_level, int active_high_low)
if ((1<<bit) & mp_ioapic_routing[ioapic].pin_programmed[idx]) {
Dprintk(KERN_DEBUG "Pin %d-%d already programmed\n",
mp_ioapic_routing[ioapic].apic_id, ioapic_pin);
- return gsi;
+ return gsi_to_irq[gsi];
}
mp_ioapic_routing[ioapic].pin_programmed[idx] |= (1<<bit);
+ if (edge_level) {
+ /*
+ * For PCI devices assign IRQs in order, avoiding gaps
+ * due to unused I/O APIC pins.
+ */
+ int irq = gsi;
+ gsi = pci_irq++;
+ gsi_to_irq[irq] = gsi;
+ }
+
io_apic_set_pci_routing(ioapic, ioapic_pin, gsi,
edge_level == ACPI_EDGE_SENSITIVE ? 0 : 1,
active_high_low == ACPI_ACTIVE_HIGH ? 0 : 1);
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