Performance tuning: single threaded userspace does not benefit from speculative page faults, so we turn them off to avoid any related (small) extra overheads. Signed-off-by: Michel Lespinasse <michel@xxxxxxxxxxxxxx> --- arch/x86/mm/fault.c | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c index 463061186827..b5c21585e35f 100644 --- a/arch/x86/mm/fault.c +++ b/arch/x86/mm/fault.c @@ -1321,6 +1321,14 @@ void do_user_addr_fault(struct pt_regs *regs, #endif #ifdef CONFIG_SPECULATIVE_PAGE_FAULT + + /* + * No need to try speculative faults for kernel or + * single threaded user space. + */ + if (!(flags & FAULT_FLAG_USER) || atomic_read(&mm->mm_users) == 1) + goto no_spf; + count_vm_event(SPF_ATTEMPT); seq = mmap_seq_read_start(mm); if (seq & 1) @@ -1353,7 +1361,9 @@ void do_user_addr_fault(struct pt_regs *regs, spf_abort: count_vm_event(SPF_ABORT); -#endif +no_spf: + +#endif /* CONFIG_SPECULATIVE_PAGE_FAULT */ /* * Kernel-mode access to the user address space should only occur -- 2.20.1
