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x86/mpx: Trace the attempts to find bounds tables 

There are two different events being traced here.  They are
doing similar things so share a trace "EVENT_CLASS" and are
presented together.

1. Trace when MPX is zapping pages "mpx_unmap_zap":

	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
	size) without decreasing the virtual space allocated
	for bounds tables.

2. Trace attempts to find bounds tables "mpx_unmap_search":

	This event traces any time we go looking to unmap a
	bounds table for a given virtual address range.  This is
	useful to ensure that the kernel actually "tried" to free
	a bounds table versus times it succeeded in finding one.

	It might try and fail if it realized that a table was
	shared with an adjacent VMA which is not being unmapped.

Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Dave Hansen <dave@sr71.net>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20150607183703.B9D2468B@viggo.jf.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Dave Hansen 2015-06-07 11:37:03 -07:00 committed by Ingo Molnar
parent 97efebf1bc
commit 2a1dcb1f79
2 changed files with 34 additions and 0 deletions
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32
arch/x86/include/asm/trace/mpx.h
View File

@ -63,6 +63,38 @@ TRACE_EVENT(bounds_exception_mpx,
__entry->bndstatus)
);
DECLARE_EVENT_CLASS(mpx_range_trace,
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
)
);
DEFINE_EVENT(mpx_range_trace, mpx_unmap_zap,
TP_PROTO(unsigned long start, unsigned long end),
TP_ARGS(start, end)
);
DEFINE_EVENT(mpx_range_trace, mpx_unmap_search,
TP_PROTO(unsigned long start, unsigned long end),
TP_ARGS(start, end)
);
#else
/*

2
arch/x86/mm/mpx.c
View File

@ -668,6 +668,7 @@ static int zap_bt_entries(struct mm_struct *mm,
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;
@ -840,6 +841,7 @@ static int mpx_unmap_tables(struct mm_struct *mm,
long __user *bd_entry, *bde_start, *bde_end;
unsigned long bt_addr;
trace_mpx_unmap_search(start, end);
/*
* "Edge" bounds tables are those which are being used by the region
* (start -> end), but that may be shared with adjacent areas. If they