From: Anton Blanchard Date: Mon, 13 Jul 2009 20:53:53 +0000 (+0000) Subject: powerpc: Preload application text segment instead of TASK_UNMAPPED_BASE X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=de4376c2846bb5a8fc6fe8dbd0e4ff30905493e6;p=GitHub%2FLineageOS%2Fandroid_kernel_motorola_exynos9610.git powerpc: Preload application text segment instead of TASK_UNMAPPED_BASE TASK_UNMAPPED_BASE is not used with the new top down mmap layout. We can reuse this preload slot by loading in the segment at 0x10000000, where almost all PowerPC binaries are linked at. On a microbenchmark that bounces a token between two 64bit processes over pipes and calls gettimeofday each iteration (to access the VDSO), both the 32bit and 64bit context switch rate improves (tested on a 4GHz POWER6): 32bit: 273k/sec -> 283k/sec 64bit: 277k/sec -> 284k/sec Signed-off-by: Anton Blanchard Signed-off-by: Benjamin Herrenschmidt --- diff --git a/arch/powerpc/mm/slb.c b/arch/powerpc/mm/slb.c index 227056c21eee..6bc8b4aeba5c 100644 --- a/arch/powerpc/mm/slb.c +++ b/arch/powerpc/mm/slb.c @@ -184,7 +184,7 @@ void switch_slb(struct task_struct *tsk, struct mm_struct *mm) unsigned long slbie_data = 0; unsigned long pc = KSTK_EIP(tsk); unsigned long stack = KSTK_ESP(tsk); - unsigned long unmapped_base; + unsigned long exec_base; if (!cpu_has_feature(CPU_FTR_NO_SLBIE_B) && offset <= SLB_CACHE_ENTRIES) { @@ -212,14 +212,13 @@ void switch_slb(struct task_struct *tsk, struct mm_struct *mm) /* * preload some userspace segments into the SLB. + * Almost all 32 and 64bit PowerPC executables are linked at + * 0x10000000 so it makes sense to preload this segment. */ - if (test_tsk_thread_flag(tsk, TIF_32BIT)) - unmapped_base = TASK_UNMAPPED_BASE_USER32; - else - unmapped_base = TASK_UNMAPPED_BASE_USER64; + exec_base = 0x10000000; if (is_kernel_addr(pc) || is_kernel_addr(stack) || - is_kernel_addr(unmapped_base)) + is_kernel_addr(exec_base)) return; slb_allocate(pc); @@ -227,9 +226,9 @@ void switch_slb(struct task_struct *tsk, struct mm_struct *mm) if (!esids_match(pc, stack)) slb_allocate(stack); - if (!esids_match(pc, unmapped_base) && - !esids_match(stack, unmapped_base)) - slb_allocate(unmapped_base); + if (!esids_match(pc, exec_base) && + !esids_match(stack, exec_base)) + slb_allocate(exec_base); } static inline void patch_slb_encoding(unsigned int *insn_addr,