Commit aec103bf authored Dec 13, 2007 by de Dinechin, Christophe (Integrity VM) Committed by Tony Luck Dec 18, 2007

[IA64] Avoid unnecessary TLB flushes when allocating memory



Improve performance of memory allocations on ia64 by avoiding a global TLB
purge to purge a single page from the file cache. This happens whenever we
evict a page from the buffer cache to make room for some other allocation.

Test case: Run 'find /usr -type f | xargs cat > /dev/null' in the
background to fill the buffer cache, then run something that uses memory,
e.g. 'gmake -j50 install'. Instrumentation showed that the number of
global TLB purges went from a few millions down to about 170 over a 12
hours run of the above.

The performance impact is particularly noticeable under virtualization,
because a virtual TLB is generally both larger and slower to purge than
a physical one.

Signed-off-by: Christophe de Dinechin <ddd@hp.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>

parent 3cdc7fc7

arch/ia64/mm/tlb.c

+15 −3

Original line number	Diff line number	Diff line
		@@ -10,6 +10,7 @@
		* IPI based ptc implementation and A-step IPI implementation.
		* 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
		*/
		#include <linux/module.h>
		#include <linux/init.h>
		@@ -89,10 +90,17 @@ ia64_global_tlb_purge (struct mm_struct *mm, unsigned long start,
		{
		static DEFINE_SPINLOCK(ptcg_lock);

		if (mm != current->active_mm \|\| !current->mm) {
		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. */
		spin_lock(&ptcg_lock);
		@@ -107,6 +115,10 @@ ia64_global_tlb_purge (struct mm_struct *mm, unsigned long start,
		} while (start < end);
		}
		spin_unlock(&ptcg_lock);

		if (mm != active_mm) {
		activate_context(active_mm);
		}
		}

		void