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[46.139.12.213]) by smtp.gmail.com with ESMTPSA id y125sm16675618wmc.39.2019.04.21.11.28.44 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Sun, 21 Apr 2019 11:28:45 -0700 (PDT) Date: Sun, 21 Apr 2019 20:28:42 +0200 From: Ingo Molnar To: Alexey Dobriyan Cc: tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, hpa@zytor.com, linux-kernel@vger.kernel.org, x86@kernel.org Subject: Re: [PATCH] x86_64: uninline TASK_SIZE Message-ID: <20190421182842.GD35603@gmail.com> References: <20190421160600.GA31092@avx2> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190421160600.GA31092@avx2> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Alexey Dobriyan 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 > --- > > 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 > +#include > +#include > + > +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