[RFC V3] Add gup trace points support

From: Yang Shi
Date: Tue Dec 08 2015 - 14:59:59 EST



v3:
* Adopted suggestion from Dave Hansen to move the gup header include to the last
* Adopted comments from Steven:
- Use DECLARE_EVENT_CLASS and DEFINE_EVENT
- Just keep necessary TP_ARGS
* Moved archtichture specific fall-backable fast version trace point after the
do while loop since it may jump to the slow version.
* Not implement recording return value since Steven plans to have it in generic
tracing code

v2:
* Adopted commetns from Steven
- remove all reference to tsk->comm since it is unnecessary for non-sched
trace points
- reduce arguments for __get_user_pages trace point and update mm/gup.c
accordingly
* Added Ralf's acked-by for patch 4/7.

There is not content change for the trace points in arch specific mm/gup.c.


Some background about why I think this might be useful.

When I was profiling some hugetlb related program, I got page-faults event
doubled when hugetlb is enabled. When I looked into the code, I found page-faults
come from two places, do_page_fault and gup. So, I tried to figure out which
play a role (or both) in my use case. But I can't find existing finer tracing
event for sub page-faults in current mainline kernel.

So, I added the gup trace points support to have finer tracing events for
page-faults. The below events are added:

__get_user_pages
__get_user_pages_fast
fixup_user_fault

Both __get_user_pages and fixup_user_fault call handle_mm_fault.

Just added trace points to raw version __get_user_pages since all variants
will call it finally to do real work.

Although __get_user_pages_fast doesn't call handle_mm_fault, it might be useful
to have it to distinguish between slow and fast version.

Yang Shi (7):
trace/events: Add gup trace events
mm/gup: add gup trace points
x86: mm/gup: add gup trace points
mips: mm/gup: add gup trace points
s390: mm/gup: add gup trace points
sh: mm/gup: add gup trace points
sparc64: mm/gup: add gup trace points

arch/mips/mm/gup.c | 7 +++++++
arch/s390/mm/gup.c | 6 ++++++
arch/sh/mm/gup.c | 7 +++++++
arch/sparc/mm/gup.c | 7 +++++++
arch/x86/mm/gup.c | 7 +++++++
include/trace/events/gup.h | 63 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
mm/gup.c | 8 ++++++++
7 files changed, 105 insertions(+)
create mode 100644 include/trace/events/gup.h
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