parisc: Use per-pagetable spinlock

PA-RISC uses a global spinlock to protect pagetable updates in the TLB
fault handlers. When multiple cores are taking TLB faults simultaneously,
the cache line containing the spinlock becomes a bottleneck.

This patch embeds the spinlock in the top level page directory, so that
every process has its own lock. It improves performance by 30% when
doing parallel compilations.

At least on the N class systems, only one PxTLB inter processor
broadcast can be active at any one time on the Merced bus. If a Merced
bus is found, this patch serializes the TLB flushes with the
pa_tlb_flush_lock spinlock.

v1: Initial patch by Mikulas
v2: Added Merced detection by Helge
v3: Revised TLB serialization by Dave & Helge

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: John David Anglin <dave.anglin@bell.net>
Signed-off-by: Helge Deller <deller@gmx.de>

1 files changed, 7 insertions, 0 deletions

diff --git a/arch/parisc/kernel/inventory.c b/arch/parisc/kernel/inventory.c
index 35d05fdd7483..6f2d611347a1 100644
--- a/arch/parisc/kernel/inventory.c
+++ b/arch/parisc/kernel/inventory.c
@@ -31,6 +31,7 @@
 #include <asm/processor.h>
 #include <asm/page.h>
 #include <asm/parisc-device.h>
+#include <asm/tlbflush.h>
 
 /*
 ** Debug options
@@ -638,4 +639,10 @@ void __init do_device_inventory(void)
 	}
 	printk(KERN_INFO "Found devices:\n");
 	print_parisc_devices();
+
+#if defined(CONFIG_64BIT) && defined(CONFIG_SMP)
+	pa_serialize_tlb_flushes = machine_has_merced_bus();
+	if (pa_serialize_tlb_flushes)
+		pr_info("Merced bus found: Enable PxTLB serialization.\n");
+#endif
 }