[IA64] Multiple outstanding ptc.g instruction support
According to SDM2.2, Itanium supports multiple outstanding ptc.g instructions.
But current kernel function ia64_global_tlb_purge() uses a spinlock to serialize
ptc.g instructions issued by multiple processors. This serialization might have
scalability issue on a big SMP machine where many processors could purge TLB
in parallel.
The patch fixes this problem by issuing multiple ptc.g instructions in
ia64_global_tlb_purge(). It also adds support for the "PALO" table to get
a platform view of the max number of outstanding ptc.g instructions (which
may be different from the processor view found from PAL_VM_SUMMARY).
PALO specification can be found at: http://www.dig64.org/home/DIG64_PALO_R1_0.pdf
spinaphore implementation by Matthew Wilcox.
Signed-off-by: Fenghua Yu <fenghua.yu@intel.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
diff --git a/arch/ia64/mm/tlb.c b/arch/ia64/mm/tlb.c
index 655da24..d41d607 100644
--- a/arch/ia64/mm/tlb.c
+++ b/arch/ia64/mm/tlb.c
@@ -11,6 +11,9 @@
* Rohit Seth <rohit.seth@intel.com>
* Ken Chen <kenneth.w.chen@intel.com>
* Christophe de Dinechin <ddd@hp.com>: Avoid ptc.e on memory allocation
+ * Copyright (C) 2007 Intel Corp
+ * Fenghua Yu <fenghua.yu@intel.com>
+ * Add multiple ptc.g/ptc.ga instruction support in global tlb purge.
*/
#include <linux/module.h>
#include <linux/init.h>
@@ -26,6 +29,7 @@
#include <asm/pal.h>
#include <asm/tlbflush.h>
#include <asm/dma.h>
+#include <asm/sal.h>
static struct {
unsigned long mask; /* mask of supported purge page-sizes */
@@ -84,14 +88,104 @@
local_flush_tlb_all();
}
+/*
+ * Implement "spinaphores" ... like counting semaphores, but they
+ * spin instead of sleeping. If there are ever any other users for
+ * this primitive it can be moved up to a spinaphore.h header.
+ */
+struct spinaphore {
+ atomic_t cur;
+};
+
+static inline void spinaphore_init(struct spinaphore *ss, int val)
+{
+ atomic_set(&ss->cur, val);
+}
+
+static inline void down_spin(struct spinaphore *ss)
+{
+ while (unlikely(!atomic_add_unless(&ss->cur, -1, 0)))
+ while (atomic_read(&ss->cur) == 0)
+ cpu_relax();
+}
+
+static inline void up_spin(struct spinaphore *ss)
+{
+ atomic_add(1, &ss->cur);
+}
+
+static struct spinaphore ptcg_sem;
+static u16 nptcg = 1;
+static int need_ptcg_sem = 1;
+static int toolatetochangeptcgsem = 0;
+
+/*
+ * Maximum number of simultaneous ptc.g purges in the system can
+ * be defined by PAL_VM_SUMMARY (in which case we should take
+ * the smallest value for any cpu in the system) or by the PAL
+ * override table (in which case we should ignore the value from
+ * PAL_VM_SUMMARY).
+ *
+ * Complicating the logic here is the fact that num_possible_cpus()
+ * isn't fully setup until we start bringing cpus online.
+ */
+void
+setup_ptcg_sem(int max_purges, int from_palo)
+{
+ static int have_palo;
+ static int firstcpu = 1;
+
+ if (toolatetochangeptcgsem) {
+ BUG_ON(max_purges < nptcg);
+ return;
+ }
+
+ if (from_palo) {
+ have_palo = 1;
+
+ /* In PALO max_purges == 0 really means it! */
+ if (max_purges == 0)
+ panic("Whoa! Platform does not support global TLB purges.\n");
+ nptcg = max_purges;
+ if (nptcg == PALO_MAX_TLB_PURGES) {
+ need_ptcg_sem = 0;
+ return;
+ }
+ goto resetsema;
+ }
+ if (have_palo) {
+ if (nptcg != PALO_MAX_TLB_PURGES)
+ need_ptcg_sem = (num_possible_cpus() > nptcg);
+ return;
+ }
+
+ /* In PAL_VM_SUMMARY max_purges == 0 actually means 1 */
+ if (max_purges == 0) max_purges = 1;
+
+ if (firstcpu) {
+ nptcg = max_purges;
+ firstcpu = 0;
+ }
+ if (max_purges < nptcg)
+ nptcg = max_purges;
+ if (nptcg == PAL_MAX_PURGES) {
+ need_ptcg_sem = 0;
+ return;
+ } else
+ need_ptcg_sem = (num_possible_cpus() > nptcg);
+
+resetsema:
+ spinaphore_init(&ptcg_sem, max_purges);
+}
+
void
ia64_global_tlb_purge (struct mm_struct *mm, unsigned long start,
unsigned long end, unsigned long nbits)
{
- static DEFINE_SPINLOCK(ptcg_lock);
-
struct mm_struct *active_mm = current->active_mm;
+ toolatetochangeptcgsem = 1;
+
if (mm != active_mm) {
/* Restore region IDs for mm */
if (mm && active_mm) {
@@ -102,19 +196,20 @@
}
}
- /* HW requires global serialization of ptc.ga. */
- spin_lock(&ptcg_lock);
- {
- do {
- /*
- * Flush ALAT entries also.
- */
- ia64_ptcga(start, (nbits<<2));
- ia64_srlz_i();
- start += (1UL << nbits);
- } while (start < end);
- }
- spin_unlock(&ptcg_lock);
+ if (need_ptcg_sem)
+ down_spin(&ptcg_sem);
+
+ do {
+ /*
+ * Flush ALAT entries also.
+ */
+ ia64_ptcga(start, (nbits << 2));
+ ia64_srlz_i();
+ start += (1UL << nbits);
+ } while (start < end);
+
+ if (need_ptcg_sem)
+ up_spin(&ptcg_sem);
if (mm != active_mm) {
activate_context(active_mm);