On Mon, 15 Jun 2020 19:19:17 -0400 Peter Xu <[email protected]> wrote:
> On Mon, Jun 15, 2020 at 03:32:40PM -0700, Linus Torvalds wrote: > > On Mon, Jun 15, 2020 at 3:16 PM Peter Xu <[email protected]> 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. Could create a new header file mm_fault.h which includes mm.h and perf_event.h. A later cleanup could move other fault-related things into that header and add the appropriate inclusions into files which use these things. btw, I think mm_account_fault() might be a better name for this function. And some (kerneldoc) documentation would be nice. Although this function is pretty self-evident. > > > > 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? Let's not add an unneeded export. If someone for some reason needs it later, it can be added then.
