From 385ea910fc28f0e46c72669a260e44d4f3f37d9e Mon Sep 17 00:00:00 2001 From: Samuel Williams Date: Tue, 16 Jul 2019 16:00:35 +1200 Subject: Add `struct fiber_pool {int free_stacks;}` to control usage of madvise. `madvise(free)` and similar operations are good because they avoid swap usage by clearing the dirty bit on memory pages which are mapped but no longer needed. However, there is some performance penalty if there is no memory pressure. Therefore, we do it by default, but it can be avoided. --- cont.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) (limited to 'cont.c') diff --git a/cont.c b/cont.c index 938db70122..16e8d7c33d 100644 --- a/cont.c +++ b/cont.c @@ -157,6 +157,9 @@ struct fiber_pool { // The initial number of stacks to allocate. size_t initial_count; + // Whether to madvise(free) the stack or not: + int free_stacks; + // The number of stacks that have been used in this pool. size_t used; @@ -479,6 +482,7 @@ fiber_pool_initialize(struct fiber_pool * fiber_pool, size_t size, size_t count, fiber_pool->size = ((size / RB_PAGE_SIZE) + 1) * RB_PAGE_SIZE; fiber_pool->count = 0; fiber_pool->initial_count = count; + fiber_pool->free_stacks = 1; fiber_pool->used = 0; fiber_pool->vm_stack_size = vm_stack_size; @@ -612,7 +616,12 @@ fiber_pool_stack_release(struct fiber_pool_stack * stack) { // Release address space and/or dirty memory: if (stack->allocation->used == 0) { fiber_pool_allocation_free(stack->allocation); - } else { + } else if (stack->pool->free_stacks) { + fiber_pool_stack_free(stack); + } +#else + // This is entirely optional, but clears the dirty flag from the stack memory, so it won't get swapped to disk when there is memory pressure: + if (stack->pool->free_stacks) { fiber_pool_stack_free(stack); } #endif -- cgit v1.2.3