v5: * Fixed a typo introduced by v4 rebase * Removed redundant "#define CREATE_TRACE_POINTS" from architecture specifc gup.c
v4: * Adopted Steven's suggestion to use "unsigned int" for nr_pages to save space in ring buffer since it is unlikely to have more than 0xffffffff pages are touched by gup in one invoke * Remove unnecessray type cast
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.
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.