On Mon, Jun 15, 2020 at 03:32:40PM -0700, Linus Torvalds wrote: > On Mon, Jun 15, 2020 at 3:16 PM Peter Xu <pet...@redhat.com> wrote: > > > > Provide this helper for doing memory page fault accounting across archs. It > > can be defined unconditionally because perf_sw_event() is always defined, > > and > > perf_sw_event() will be a no-op if !CONFIG_PERF_EVENTS. > > Well, the downside is that now it forces a separate I$ miss and all > those extra arguments because it's a out-of-line function and the > compiler won't see that they all go away. > > Yeah, maybe some day maybe we'll have LTO and these kinds of things > will not matter. And maybe they already don't. But it seems kind of > sad to basically force non-optimal code generation from this series.
I tried to make it static inline firstly in linux/mm.h, however it'll need to have linux/mm.h include linux/perf_event.h which seems to have created a loop dependency of headers. I verified current code will at least generate inlined functions too for x86 (no mm_fault_accounting() in "objdump -t vmlinux") with gcc10. Another alternative is to make it a macro, it's just that I feel the function definition is a bit cleaner. Any further suggestions welcomed too. > > Why would you export the symbol, btw? Page fault handling is never a module. I followed handle_mm_fault() which is exported too, since potentially mm_fault_accounting() should always be called in the same context of handle_mm_fault(). Or do you prefer me to drop it? Thanks, -- Peter Xu
