On April 21, 2019 11:28:42 AM PDT, Ingo Molnar <mi...@kernel.org> wrote: > >* Alexey Dobriyan <adobri...@gmail.com> wrote: > >> TASK_SIZE macro is quite deceptive: it looks like a constant but in >fact >> compiles to 50+ bytes. >> >> Space savings on x86_64 defconfig: >> >> add/remove: 1/0 grow/shrink: 3/24 up/down: 77/-2247 (-2170) >> Function old new delta >> _task_size - 52 +52 >> mpol_shared_policy_init 344 363 +19 >> shmem_get_unmapped_area 92 97 +5 >> __rseq_handle_notify_resume.cold 34 35 +1 >> copy_from_user_nmi 123 113 -10 >> mmap_address_hint_valid 92 56 -36 >> arch_get_unmapped_area_topdown 471 435 -36 >> tlb_gather_mmu 164 126 -38 >> hugetlb_get_unmapped_area 774 736 -38 >> __create_xol_area 497 458 -39 >> arch_tlb_gather_mmu 160 120 -40 >> setup_new_exec 380 336 -44 >> __x64_sys_mlockall 378 333 -45 >> __ia32_sys_mlockall 378 333 -45 >> tlb_flush_mmu 235 189 -46 >> unmap_page_range 2098 2048 -50 >> copy_mount_options 518 465 -53 >> __get_user_pages 1737 1675 -62 >> get_unmapped_area 270 204 -66 >> perf_prepare_sample 1176 1098 -78 >> perf_callchain_user 549 469 -80 >> mremap_to.isra 545 457 -88 >> arch_tlb_finish_mmu 394 305 -89 >> __do_munmap 1039 927 -112 >> elf_map 527 409 -118 >> prctl_set_mm 1509 1335 -174 >> __rseq_handle_notify_resume 1116 906 -210 >> load_elf_binary 11761 11111 -650 >> Total: Before=14121337, After=14119167, chg -0.02% >> >> Signed-off-by: Alexey Dobriyan <adobri...@gmail.com> >> --- >> >> arch/x86/include/asm/processor.h | 4 ++-- >> arch/x86/kernel/Makefile | 1 + >> arch/x86/kernel/task_size_64.c | 9 +++++++++ >> 3 files changed, 12 insertions(+), 2 deletions(-) >> >> --- a/arch/x86/include/asm/processor.h >> +++ b/arch/x86/include/asm/processor.h >> @@ -887,8 +887,8 @@ static inline void spin_lock_prefetch(const void >*x) >> >> #define TASK_SIZE_LOW (test_thread_flag(TIF_ADDR32) ? \ >> IA32_PAGE_OFFSET : DEFAULT_MAP_WINDOW) >> -#define TASK_SIZE (test_thread_flag(TIF_ADDR32) ? \ >> - IA32_PAGE_OFFSET : TASK_SIZE_MAX) >> +unsigned long _task_size(void); >> +#define TASK_SIZE _task_size() >> #define TASK_SIZE_OF(child) ((test_tsk_thread_flag(child, >TIF_ADDR32)) ? \ >> IA32_PAGE_OFFSET : TASK_SIZE_MAX) >> >> --- a/arch/x86/kernel/Makefile >> +++ b/arch/x86/kernel/Makefile >> @@ -46,6 +46,7 @@ CFLAGS_irq.o := -I$(src)/../include/asm/trace >> >> obj-y := process_$(BITS).o signal.o >> obj-$(CONFIG_COMPAT) += signal_compat.o >> +obj-$(CONFIG_X86_64) += task_size_64.o >> obj-y += traps.o idt.o irq.o irq_$(BITS).o >> dumpstack_$(BITS).o >> obj-y += time.o ioport.o dumpstack.o nmi.o >> obj-$(CONFIG_MODIFY_LDT_SYSCALL) += ldt.o >> new file mode 100644 >> --- /dev/null >> +++ b/arch/x86/kernel/task_size_64.c >> @@ -0,0 +1,9 @@ >> +#include <linux/export.h> >> +#include <linux/sched.h> >> +#include <linux/thread_info.h> >> + >> +unsigned long _task_size(void) >> +{ >> + return test_thread_flag(TIF_ADDR32) ? IA32_PAGE_OFFSET : >TASK_SIZE_MAX; >> +} >> +EXPORT_SYMBOL(_task_size); > >Good idea - but instead of adding yet another compilation unit, why not > >stick _task_size() into arch/x86/kernel/process_64.c, which is the >canonical place for process management related arch functions? > >Thanks, > > Ingo
Better yet... since TIF_ADDR32 isn't something that changes randomly, perhaps this should be a separate variable? -- Sent from my Android device with K-9 Mail. Please excuse my brevity.