KAMEZAWA Hiroyuki wrote:
> One aspect of difference in reclaim logic between global lru and memcg is
> * global LRU triggers memory reclaim at memory shortage.
> * memcg LRU triggers memory reclaim at excess of usage.
>
> Then, global LRU _know_ which node we should start reclaim from.
> * start from a node at memory shortage or
> * start from a node where memory allocation is waiting
>
> WRT memcg, it's difficult to find where we should start because
> there is no memory shortage and LRU is splitted.
> (But per-zone-LRU is definitely necessary for scalability.)
>
> This patch tries to deteremine a node for starting recalim by checking
> ratio of inactive pages/active pages in a node. And trying to avoid starting
> from a node with relatively small usage.
> Better algorithm is welcome.
>
> Singed-off-by: KAMEZAWA Hiruyuki <[EMAIL PROTECTED]>
>
> Index: mm-2.6.26-rc2-mm1/mm/memcontrol.c
> ===================================================================
> --- mm-2.6.26-rc2-mm1.orig/mm/memcontrol.c
> +++ mm-2.6.26-rc2-mm1/mm/memcontrol.c
> @@ -578,7 +578,7 @@ retry:
> if (state == RES_OVER_LIMIT) {
> if (!(gfp_mask & __GFP_WAIT))
> goto out;
> - if (try_to_free_mem_cgroup_pages(mem, gfp_mask))
> + if (try_to_free_mem_cgroup_pages(mem, -1, gfp_mask))
> goto retry;
> /*
> * try_to_free_mem_cgroup_pages() might not give us a
> @@ -801,7 +801,7 @@ int mem_cgroup_shrink_usage(struct mm_st
> rcu_read_unlock();
>
> do {
> - progress = try_to_free_mem_cgroup_pages(mem, gfp_mask);
> + progress = try_to_free_mem_cgroup_pages(mem, -1, gfp_mask);
> } while (!progress && --retry);
>
> if (!retry)
> @@ -814,7 +814,7 @@ static void mem_cgroup_drop_all_pages(st
> {
> int progress;
> while (!res_counter_empty(&mem->res)) {
> - progress = try_to_free_mem_cgroup_pages(mem,
> + progress = try_to_free_mem_cgroup_pages(mem, -1,
> GFP_HIGHUSER_MOVABLE);
> if (!progress) /* we did as much as possible */
> break;
> @@ -912,6 +912,62 @@ out:
> /*
> * background reclaim daemon.
> */
> +
> +#ifdef CONFIG_NUMA
> +/*
> + * Because memory controller's memory reclaim doesn't come from memory
> shortage,
> + * we cannot know which node should be reclaimed in an easy way.
> + * This routine select a node with inactive pages to be a node for starting
> + * scanning.
> + */
> +int __select_best_node(struct mem_cgroup *mem)
> +{
> + int nid;
> + int best_node = -1;
> + unsigned long highest_inactive_ratio = 0;
> + unsigned long active, inactive, inactive_ratio, total, threshold, flags;
> + struct mem_cgroup_per_zone *mz;
> + int zid;
> +
> + /*
> + * When a node's memory usage is smaller than
> + * total_usage/num_of_node * 75%, we don't select the node
> + */
> + total = mem->res.usage >> PAGE_SHIFT;
> + threshold = (total / num_node_state(N_HIGH_MEMORY)) * 3 / 4;
> +
> + /*
> + * See nodemask.h, N_HIGH_MEMORY means that a node has memory
> + * can be used for user's memory.(i.e. not means HIGHMEM).
> + */
> + for_each_node_state(nid, N_HIGH_MEMORY) {
> + active = 0;
> + inactive = 0;
> +
> + for (zid = 0; zid < MAX_NR_ZONES; zid++) {
> + mz = mem_cgroup_zoneinfo(mem, nid, zid);
> + spin_lock_irqsave(&mz->lru_lock, flags);
> + active += MEM_CGROUP_ZSTAT(mz, MEM_CGROUP_ZSTAT_ACTIVE);
> + inactive +=
> + MEM_CGROUP_ZSTAT(mz, MEM_CGROUP_ZSTAT_INACTIVE);
> + spin_unlock_irqrestore(&mz->lru_lock, flags);
> + }
> +
> + if (active + inactive < threshold)
> + continue;
> + inactive_ratio = (inactive * 100) / (active + 1);
> + if (inactive_ratio > highest_inactive_ratio)
> + best_node = nid;
Shouldn't we update highest_inactive_ration here?
> + }
> + return best_node;
> +}
> +#else
> +int __select_best_node(struct mem_cgroup *mem)
> +{
> + return 0;
> +}
> +#endif
> +
> static int mem_cgroup_reclaim_daemon(void *data)
> {
> DEFINE_WAIT(wait);
> @@ -935,13 +991,9 @@ static int mem_cgroup_reclaim_daemon(voi
> continue;
> }
> finish_wait(&mem->daemon.waitq, &wait);
> - /*
> - * memory resource controller doesn't see NUMA memory usage
> - * balancing, becasue we cannot know what balancing is good.
> - * TODO: some annotation or heuristics to detect which node
> - * we should start reclaim from.
> - */
> - ret = try_to_free_mem_cgroup_pages(mem, GFP_HIGHUSER_MOVABLE);
> +
> + ret = try_to_free_mem_cgroup_pages(mem,
> + __select_best_node(mem), GFP_HIGHUSER_MOVABLE);
>
> yield();
> }
> Index: mm-2.6.26-rc2-mm1/mm/vmscan.c
> ===================================================================
> --- mm-2.6.26-rc2-mm1.orig/mm/vmscan.c
> +++ mm-2.6.26-rc2-mm1/mm/vmscan.c
> @@ -1429,7 +1429,7 @@ unsigned long try_to_free_pages(struct z
> #ifdef CONFIG_CGROUP_MEM_RES_CTLR
>
> unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem_cont,
> - gfp_t gfp_mask)
> + int nid, gfp_t gfp_mask)
> {
> struct scan_control sc = {
> .may_writepage = !laptop_mode,
> @@ -1442,9 +1442,11 @@ unsigned long try_to_free_mem_cgroup_pag
> };
> struct zonelist *zonelist;
>
> + if (nid == -1)
> + nid = numa_node_id();
> sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
> (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK);
> - zonelist = NODE_DATA(numa_node_id())->node_zonelists;
> + zonelist = NODE_DATA(nid)->node_zonelists;
> return do_try_to_free_pages(zonelist, &sc);
> }
> #endif
> Index: mm-2.6.26-rc2-mm1/include/linux/swap.h
> ===================================================================
> --- mm-2.6.26-rc2-mm1.orig/include/linux/swap.h
> +++ mm-2.6.26-rc2-mm1/include/linux/swap.h
> @@ -184,7 +184,7 @@ extern void swap_setup(void);
> extern unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
> gfp_t gfp_mask);
> extern unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem,
> - gfp_t gfp_mask);
> + int nid, gfp_t gfp_mask);
> extern int __isolate_lru_page(struct page *page, int mode);
> extern unsigned long shrink_all_memory(unsigned long nr_pages);
> extern int vm_swappiness;
>
--
Warm Regards,
Balbir Singh
Linux Technology Center
IBM, ISTL
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