[PATCH 05/17] x86, mpx: trace when MPX is zapping pages

Dave Hansen
2015-03-26T18:33:33Z

From: Dave Hansen <dave.hansen@linux.intel.com>

When MPX can not free an entire bounds table, it will instead
try to zap unused parts of a bounds table to free the backing
memory. This decreases Rss (resident set) without decreasing
the virtual space allocated for bounds tables.

Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
---

b/arch/x86/include/asm/trace/mpx.h | 22 ++++++++++++++++++++++
b/arch/x86/mm/mpx.c | 1 +
2 files changed, 23 insertions(+)

diff -puN arch/x86/include/asm/trace/mpx.h~mpx-trace_unmap_zap arch/x86/include/asm/trace/mpx.h
--- a/arch/x86/include/asm/trace/mpx.h~mpx-trace_unmap_zap 2015-03-26 11:27:06.279273832 -0700
+++ b/arch/x86/include/asm/trace/mpx.h 2015-03-26 11:27:06.283274012 -0700
@@ -53,6 +53,28 @@ TRACE_EVENT(bounds_exception_mpx,
__entry->bndstatus)
);

+TRACE_EVENT(mpx_unmap_zap,
+
+ TP_PROTO(unsigned long start,
+ unsigned long end),
+ TP_ARGS(start, end),
+
+ TP_STRUCT__entry(
+ __field(unsigned long, start)
+ __field(unsigned long, end)
+ ),
+
+ TP_fast_assign(
+ __entry->start = start;
+ __entry->end = end;
+ ),
+
+ TP_printk("0x%p -> 0x%p",
+ (void *)__entry->start,
+ (void *)__entry->end
+ )
+);
+
#else

/*
diff -puN arch/x86/mm/mpx.c~mpx-trace_unmap_zap arch/x86/mm/mpx.c
--- a/arch/x86/mm/mpx.c~mpx-trace_unmap_zap 2015-03-26 11:27:06.280273877 -0700
+++ b/arch/x86/mm/mpx.c 2015-03-26 11:27:06.284274058 -0700
@@ -670,6 +670,7 @@ static int zap_bt_entries(struct mm_stru

len = min(vma->vm_end, end) - addr;
zap_page_range(vma, addr, len, NULL);
+ trace_mpx_unmap_zap(addr, addr+len);

vma = vma->vm_next;
addr = vma->vm_start;
_