(2014/08/26 14:30), Lucas De Marchi wrote: > On Mon, Aug 25, 2014 at 10:55:48AM +0000, Masami Hiramatsu wrote: >> Lock-up a module in kernel so that it is not removed unless >> forcibly unload. This is done by loading a module with >> MODULE_INIT_LOCKUP_MODULE flag (via finit_module). >> This speeds up try_module_get by skipping refcount inc/dec for >> the locked modules. >> >> Note that this flag requires to update libkmod to support it. > > Patches to kmod go to linux-modules@xxxxxxxxxxxxxxx OK, thanks. I'll send another series for it. > However I'm skeptical with the use case of this flag. Is this only so > that try_module_get() is a little bit faster? How much? For the performance side of refcounting, I guess it has no recognizable difference compared with current one. It may be a little faster than atomic_t ref-counter, and actual overhead will strongly depends on the hardware configuration. So, I can just drop this "lockup" patch from this series, if nobody complains about using atomic_t ref-counter instead of module_ref. I'd just like to get rid of the stop_machine() from unloading :) > Then this would depend on a flag the user passed to modprobe which means > only a few modules will use the flag. If you change the default > behavior in kmod to pass this flag always, then any module the user > wants to remove will need to be forcibly removed. I saw an environmental variable to control it (MODPROBE_OPTIONS). So if a user (e.g. systemtap :) ) want to make it removable, he/she can change the env-var before running the command. > > I'm leaving the rest of the patch here since I'm CC'ing linux-modules. > Thank you, -- Masami HIRAMATSU Software Platform Research Dept. Linux Technology Research Center Hitachi, Ltd., Yokohama Research Laboratory E-mail: masami.hiramatsu.pt@xxxxxxxxxxx -- To unsubscribe from this list: send the line "unsubscribe linux-modules" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
