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authorAnil S Keshavamurthy <anil.s.keshavamurthy@intel.com>2006-06-26 03:25:25 -0400
committerLinus Torvalds <torvalds@g5.osdl.org>2006-06-26 12:58:22 -0400
commit1bd858a507937cef6e8ca5efc6820a5744e73683 (patch)
tree2c935864cb3375c16aa7a2fd84d797aca78afd14
parent36721656776f177280ccb50477a02e86e6444292 (diff)
[PATCH] Notify page fault call chain for x86_64
Currently in the do_page_fault() code path, we call notify_die(DIE_PAGE_FAULT, ...) to notify the page fault. Since notify_die() is highly overloaded, this page fault notification is currently being sent to all the components registered with register_die_notification() which uses the same die_chain to loop for all the registered components which is unnecessary. In order to optimize the do_page_fault() code path, this critical page fault notification is now moved to different call chain and the test results showed great improvements. And the kprobes which is interested in this notifications, now registers onto this new call chain only when it need to, i.e Kprobes now registers for page fault notification only when their are an active probes and unregisters from this page fault notification when no probes are active. I have incorporated all the feedback given by Ananth and Keith and everyone, and thanks for all the review feedback. This patch: Overloading of page fault notification with the notify_die() has performance issues(since the only interested components for page fault is kprobes and/or kdb) and hence this patch introduces the new notifier call chain exclusively for page fault notifications their by avoiding notifying unnecessary components in the do_page_fault() code path. Signed-off-by: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
-rw-r--r--arch/x86_64/mm/fault.c39
-rw-r--r--include/asm-x86_64/kdebug.h2
2 files changed, 39 insertions, 2 deletions
diff --git a/arch/x86_64/mm/fault.c b/arch/x86_64/mm/fault.c
index 55250593d8c9..0803d3858af1 100644
--- a/arch/x86_64/mm/fault.c
+++ b/arch/x86_64/mm/fault.c
@@ -41,6 +41,41 @@
41#define PF_RSVD (1<<3) 41#define PF_RSVD (1<<3)
42#define PF_INSTR (1<<4) 42#define PF_INSTR (1<<4)
43 43
44#ifdef CONFIG_KPROBES
45ATOMIC_NOTIFIER_HEAD(notify_page_fault_chain);
46
47/* Hook to register for page fault notifications */
48int register_page_fault_notifier(struct notifier_block *nb)
49{
50 vmalloc_sync_all();
51 return atomic_notifier_chain_register(&notify_page_fault_chain, nb);
52}
53
54int unregister_page_fault_notifier(struct notifier_block *nb)
55{
56 return atomic_notifier_chain_unregister(&notify_page_fault_chain, nb);
57}
58
59static inline int notify_page_fault(enum die_val val, const char *str,
60 struct pt_regs *regs, long err, int trap, int sig)
61{
62 struct die_args args = {
63 .regs = regs,
64 .str = str,
65 .err = err,
66 .trapnr = trap,
67 .signr = sig
68 };
69 return atomic_notifier_call_chain(&notify_page_fault_chain, val, &args);
70}
71#else
72static inline int notify_page_fault(enum die_val val, const char *str,
73 struct pt_regs *regs, long err, int trap, int sig)
74{
75 return NOTIFY_DONE;
76}
77#endif
78
44void bust_spinlocks(int yes) 79void bust_spinlocks(int yes)
45{ 80{
46 int loglevel_save = console_loglevel; 81 int loglevel_save = console_loglevel;
@@ -348,7 +383,7 @@ asmlinkage void __kprobes do_page_fault(struct pt_regs *regs,
348 if (vmalloc_fault(address) >= 0) 383 if (vmalloc_fault(address) >= 0)
349 return; 384 return;
350 } 385 }
351 if (notify_die(DIE_PAGE_FAULT, "page fault", regs, error_code, 14, 386 if (notify_page_fault(DIE_PAGE_FAULT, "page fault", regs, error_code, 14,
352 SIGSEGV) == NOTIFY_STOP) 387 SIGSEGV) == NOTIFY_STOP)
353 return; 388 return;
354 /* 389 /*
@@ -358,7 +393,7 @@ asmlinkage void __kprobes do_page_fault(struct pt_regs *regs,
358 goto bad_area_nosemaphore; 393 goto bad_area_nosemaphore;
359 } 394 }
360 395
361 if (notify_die(DIE_PAGE_FAULT, "page fault", regs, error_code, 14, 396 if (notify_page_fault(DIE_PAGE_FAULT, "page fault", regs, error_code, 14,
362 SIGSEGV) == NOTIFY_STOP) 397 SIGSEGV) == NOTIFY_STOP)
363 return; 398 return;
364 399
diff --git a/include/asm-x86_64/kdebug.h b/include/asm-x86_64/kdebug.h
index cf795631d9b4..cd52c7f33bca 100644
--- a/include/asm-x86_64/kdebug.h
+++ b/include/asm-x86_64/kdebug.h
@@ -15,6 +15,8 @@ struct die_args {
15 15
16extern int register_die_notifier(struct notifier_block *); 16extern int register_die_notifier(struct notifier_block *);
17extern int unregister_die_notifier(struct notifier_block *); 17extern int unregister_die_notifier(struct notifier_block *);
18extern int register_page_fault_notifier(struct notifier_block *);
19extern int unregister_page_fault_notifier(struct notifier_block *);
18extern struct atomic_notifier_head die_chain; 20extern struct atomic_notifier_head die_chain;
19 21
20/* Grossly misnamed. */ 22/* Grossly misnamed. */