Messages in this thread | | | Subject | Re: [PATCH 3/4] kernel/fork: switch vmapped stack callation to __vmalloc_area() | From | Konstantin Khlebnikov <> | Date | Tue, 23 Jan 2018 16:57:21 +0300 |
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# stress-ng --clone 100 -t 10s --metrics-brief at 32-core machine shows boost 35000 -> 36000 bogo ops
Patch 4/4 is a kind of RFC. Actually per-cpu cache of preallocated stacks works faster than buddy allocator thus performance boots for it happens only at completely insane rate of clones.
On 23.01.2018 13:55, Konstantin Khlebnikov wrote: > This gives as pointer vm_struct without calling find_vm_area(). > > And fix comment about that task holds cache of vm area: this cache used > for retrieving actual stack pages, freeing is done by vfree_deferred(). > > Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru> > --- > kernel/fork.c | 37 +++++++++++++++---------------------- > 1 file changed, 15 insertions(+), 22 deletions(-) > > diff --git a/kernel/fork.c b/kernel/fork.c > index 2295fc69717f..457c9151f3c8 100644 > --- a/kernel/fork.c > +++ b/kernel/fork.c > @@ -204,39 +204,32 @@ static int free_vm_stack_cache(unsigned int cpu) > static unsigned long *alloc_thread_stack_node(struct task_struct *tsk, int node) > { > #ifdef CONFIG_VMAP_STACK > - void *stack; > + struct vm_struct *stack; > int i; > > for (i = 0; i < NR_CACHED_STACKS; i++) { > - struct vm_struct *s; > - > - s = this_cpu_xchg(cached_stacks[i], NULL); > - > - if (!s) > + stack = this_cpu_xchg(cached_stacks[i], NULL); > + if (!stack) > continue; > > #ifdef CONFIG_DEBUG_KMEMLEAK > /* Clear stale pointers from reused stack. */ > - memset(s->addr, 0, THREAD_SIZE); > + memset(stack->addr, 0, THREAD_SIZE); > #endif > - tsk->stack_vm_area = s; > - return s->addr; > + tsk->stack_vm_area = stack; > + return stack->addr; > } > > - stack = __vmalloc_node_range(THREAD_SIZE, THREAD_ALIGN, > - VMALLOC_START, VMALLOC_END, > - THREADINFO_GFP, > - PAGE_KERNEL, > - 0, node, __builtin_return_address(0)); > + stack = __vmalloc_area(THREAD_SIZE, THREAD_ALIGN, > + VMALLOC_START, VMALLOC_END, > + THREADINFO_GFP, PAGE_KERNEL, > + 0, node, __builtin_return_address(0)); > + if (unlikely(!stack)) > + return NULL; > > - /* > - * We can't call find_vm_area() in interrupt context, and > - * free_thread_stack() can be called in interrupt context, > - * so cache the vm_struct. > - */ > - if (stack) > - tsk->stack_vm_area = find_vm_area(stack); > - return stack; > + /* Cache the vm_struct for stack to page conversions. */ > + tsk->stack_vm_area = stack; > + return stack->addr; > #else > struct page *page = alloc_pages_node(node, THREADINFO_GFP, > THREAD_SIZE_ORDER); >
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