From 2a1dcb1f796ad37028df37d96fc7c5b6b1705a43 Mon Sep 17 00:00:00 2001 From: Dave Hansen Date: Sun, 7 Jun 2015 11:37:03 -0700 Subject: 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 Reviewed-by: Thomas Gleixner Cc: Andrew Morton Cc: Dave Hansen Cc: H. Peter Anvin Cc: Linus Torvalds Cc: Peter Zijlstra Link: http://lkml.kernel.org/r/20150607183703.B9D2468B@viggo.jf.intel.com Signed-off-by: Ingo Molnar --- arch/x86/mm/mpx.c | 2 ++ 1 file changed, 2 insertions(+) (limited to 'arch/x86/mm/mpx.c') diff --git a/arch/x86/mm/mpx.c b/arch/x86/mm/mpx.c index 75e5d7043f65..55729ee9263e 100644 --- a/arch/x86/mm/mpx.c +++ b/arch/x86/mm/mpx.c @@ -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 -- cgit 1.4.1