The patch below improves performance when the system is under memory
pressure, by avoiding a TLB purge (broadcast on all processors) just to
purge a single page. This case is frequently seen when the system tries
to evict buffer cache memory to make room for something else.
An easy reproducer is to run 'find /usr -type f | xargs cat > /dev/null'
to fill the buffer cache on a more or less continuous basis, while doing
a gmake -j50 install on a 4-way box to keep allocating memory.
Instrumentation showed that the number of global TLB purges went from a
few millions down to about 170 over a 12 hours run.
Opinions?
Regards,
Christophe
diff -Naur linux-2.6.20.3/arch/ia64/mm/tlb.c
linux-2.6.20.3-ptce-avoidance/arch/ia64/mm/tlb.c
--- linux-2.6.20.3/arch/ia64/mm/tlb.c 2007-03-13 19:27:08.000000000
+0100
+++ linux-2.6.20.3-ptce-avoidance/arch/ia64/mm/tlb.c 2007-03-14
23:32:59.000000000 +0100
@@ -10,6 +10,7 @@
* IPI based ptc implementation and A-step IPI
implementation.
* Rohit Seth <rohit.seth@xxxxxxxxx>
* Ken Chen <kenneth.w.chen@xxxxxxxxx>
+ * Christophe de Dinechin <ddd@xxxxxx>: Avoid ptc.e on memory
allocation
*/
#include <linux/module.h>
#include <linux/init.h>
@@ -89,9 +90,16 @@
{
static DEFINE_SPINLOCK(ptcg_lock);
- if (mm != current->active_mm || !current->mm) {
- flush_tlb_all();
- return;
+ struct mm_struct *active_mm = current->active_mm;
+
+ if (mm != active_mm) {
+ /* Restore region IDs for mm */
+ if (mm && active_mm) {
+ activate_context(mm);
+ } else {
+ flush_tlb_all();
+ return;
+ }
}
/* HW requires global serialization of ptc.ga. */
@@ -107,6 +115,10 @@
} while (start < end);
}
spin_unlock(&ptcg_lock);
+
+ if (mm != active_mm) {
+ activate_context(active_mm);
+ }
}
void
-
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