linux-kernel - [PATCH] x86/irq: optimizing nr

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Message-ID: <498EA964.2070902@kernel.org>
Date:	Sun, 08 Feb 2009 01:44:04 -0800
From:	Yinghai Lu <yinghai@...nel.org>
To:	Ingo Molnar <mingo@...e.hu>, Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	Andrew Morton <akpm@...ux-foundation.org>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: [PATCH] x86/irq: optimizing nr_irqs -v2


Impact: more depend on cards to be used

depend on nr_irq_gsi more, and have a ratio for MSI

v2: make nr_irqs shoule less than NR_VECTORS * nr_cpu_ids
   aka if only one cpu, we only can support nr_irqs = NR_VECTORS

Signed-off-by: Yinghai Lu <yinghai@...nel.org>

---
 arch/x86/kernel/io_apic.c |   16 +++++++++++-----
 1 file changed, 11 insertions(+), 5 deletions(-)

Index: linux-2.6/arch/x86/kernel/io_apic.c
===================================================================
--- linux-2.6.orig/arch/x86/kernel/io_apic.c
+++ linux-2.6/arch/x86/kernel/io_apic.c
@@ -3482,9 +3482,9 @@ int arch_setup_msi_irqs(struct pci_dev *
 	sub_handle = 0;
 	list_for_each_entry(msidesc, &dev->msi_list, list) {
 		irq = create_irq_nr(irq_want);
-		irq_want++;
 		if (irq == 0)
 			return -1;
+		irq_want = irq + 1;
 #ifdef CONFIG_INTR_REMAP
 		if (!intr_remapping_enabled)
 			goto no_ir;
@@ -3838,11 +3838,17 @@ int __init arch_probe_nr_irqs(void)
 {
 	int nr;
 
-	nr = ((8 * nr_cpu_ids) > (32 * nr_ioapics) ?
-		(NR_VECTORS + (8 * nr_cpu_ids)) :
-		(NR_VECTORS + (32 * nr_ioapics)));
+	if (nr_irqs > (NR_VECTORS * nr_cpu_ids))
+		nr_irqs = NR_VECTORS * nr_cpu_ids;
 
-	if (nr < nr_irqs && nr > nr_irqs_gsi)
+	nr = nr_irqs_gsi + 8 * nr_cpu_ids;
+#if defined(CONFIG_PCI_MSI) || defined(CONFIG_HT_IRQ)
+	/*
+	 * for MSI and HT dyn irq
+	 */
+	nr += nr_irqs_gsi * 16;
+#endif
+	if (nr < nr_irqs)
 		nr_irqs = nr;
 
 	return 0;
--
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