[Xen-devel] [PATCH] x86: add perf counter for pointless updates of writable pages through a hypercall

["Jan Beulich" <jbeulich@xxxxxxxxxx>]

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxxxx>

Index: 2008-06-12/xen/arch/x86/mm.c
===================================================================
--- 2008-06-12.orig/xen/arch/x86/mm.c   2008-06-12 09:04:50.000000000 +0200
+++ 2008-06-12/xen/arch/x86/mm.c        2008-06-12 09:08:36.000000000 +0200
@@ -2606,6 +2606,8 @@ int do_mmu_update(
                 if ( unlikely(!get_page_type(page, PGT_writable_page)) )
                     break;
 
+                perfc_incr(writable_mmu_updates);
+
                 okay = paging_write_guest_entry(v, va, req.val, _mfn(mfn));
 
                 put_page_type(page);
Index: 2008-06-12/xen/include/asm-x86/perfc_defn.h
===================================================================
--- 2008-06-12.orig/xen/include/asm-x86/perfc_defn.h    2008-06-10 
18:00:41.000000000 +0200
+++ 2008-06-12/xen/include/asm-x86/perfc_defn.h 2008-06-12 09:08:36.000000000 
+0200
@@ -23,6 +23,7 @@ PERFCOUNTER(calls_to_mmuext_op,         
 PERFCOUNTER(num_mmuext_ops,             "mmuext ops")
 PERFCOUNTER(calls_to_mmu_update,        "calls to mmu_update")
 PERFCOUNTER(num_page_updates,           "page updates")
+PERFCOUNTER(writable_mmu_updates,       "mmu_update-s of writable pages")
 PERFCOUNTER(calls_to_update_va,         "calls to update_va_map")
 PERFCOUNTER(page_faults,            "page faults")
 PERFCOUNTER(copy_user_faults,       "copy_user faults")




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