On Sun, Apr 17, 2011 at 8:51 PM, Minchan Kim wrote: > On Sat, Apr 16, 2011 at 8:23 AM, Ying Han wrote: > > This is the main loop of per-memcg background reclaim which is > implemented in > > function balance_mem_cgroup_pgdat(). > > > > The function performs a priority loop similar to global reclaim. During > each > > iteration it invokes balance_pgdat_node() for all nodes on the system, > which > > is another new function performs background reclaim per node. After > reclaiming > > each node, it checks mem_cgroup_watermark_ok() and breaks the priority > loop if > > it returns true. > > > > changelog v5..v4: > > 1. remove duplicate check on nodes_empty() > > 2. add logic to check if the per-memcg lru is empty on the zone. > > 3. make per-memcg kswapd to reclaim SWAP_CLUSTER_MAX per zone. It make > senses > > since it helps to balance the pressure across zones within the memcg. > > > > changelog v4..v3: > > 1. split the select_victim_node and zone_unreclaimable to a seperate > patches > > 2. remove the logic tries to do zone balancing. > > > > changelog v3..v2: > > 1. change mz->all_unreclaimable to be boolean. > > 2. define ZONE_RECLAIMABLE_RATE macro shared by zone and per-memcg > reclaim. > > 3. some more clean-up. > > > > changelog v2..v1: > > 1. move the per-memcg per-zone clear_unreclaimable into uncharge stage. > > 2. shared the kswapd_run/kswapd_stop for per-memcg and global background > > reclaim. > > 3. name the per-memcg memcg as "memcg-id" (css->id). And the global > kswapd > > keeps the same name. > > 4. fix a race on kswapd_stop while the per-memcg-per-zone info could be > accessed > > after freeing. > > 5. add the fairness in zonelist where memcg remember the last zone > reclaimed > > from. > > > > Signed-off-by: Ying Han > > --- > > mm/vmscan.c | 157 > +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ > > 1 files changed, 157 insertions(+), 0 deletions(-) > > > > diff --git a/mm/vmscan.c b/mm/vmscan.c > > index 06036d2..39e6300 100644 > > --- a/mm/vmscan.c > > +++ b/mm/vmscan.c > > @@ -47,6 +47,8 @@ > > > > #include > > > > +#include > > + > > #include "internal.h" > > > > #define CREATE_TRACE_POINTS > > @@ -111,6 +113,8 @@ struct scan_control { > > * are scanned. > > */ > > nodemask_t *nodemask; > > + > > + int priority; > > }; > > > > #define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru)) > > @@ -2631,11 +2635,164 @@ static void kswapd_try_to_sleep(struct kswapd > *kswapd_p, int order, > > finish_wait(wait_h, &wait); > > } > > > > +#ifdef CONFIG_CGROUP_MEM_RES_CTLR > > +/* > > + * The function is used for per-memcg LRU. It scanns all the zones of > the > > + * node and returns the nr_scanned and nr_reclaimed. > > + */ > > +static void balance_pgdat_node(pg_data_t *pgdat, int order, > > + struct scan_control *sc) > > +{ > > + int i; > > + unsigned long total_scanned = 0; > > + struct mem_cgroup *mem_cont = sc->mem_cgroup; > > + int priority = sc->priority; > > + enum lru_list l; > > + > > + /* > > + * This dma->highmem order is consistant with global reclaim. > > + * We do this because the page allocator works in the opposite > > + * direction although memcg user pages are mostly allocated at > > + * highmem. > > + */ > > + for (i = 0; i < pgdat->nr_zones; i++) { > > + struct zone *zone = pgdat->node_zones + i; > > + unsigned long scan = 0; > > + > > + for_each_evictable_lru(l) > > + scan += mem_cgroup_zone_nr_pages(mem_cont, zone, > l); > > + > > + if (!populated_zone(zone) || !scan) > > + continue; > > Do we really need this double check? Isn't only _scan_ check enough? > yes. will change on next post. > And shouldn't we consider non-swap case? > good point. we don't need to count the anon lru in non-swap case. A new function will be added to count the memcg_zone_reclaimable per zone. > > > + > > + sc->nr_scanned = 0; > > + shrink_zone(priority, zone, sc); > > + total_scanned += sc->nr_scanned; > > + > > + /* > > + * If we've done a decent amount of scanning and > > + * the reclaim ratio is low, start doing writepage > > + * even in laptop mode > > + */ > > + if (total_scanned > SWAP_CLUSTER_MAX * 2 && > > + total_scanned > sc->nr_reclaimed + sc->nr_reclaimed / > 2) { > > + sc->may_writepage = 1; > > I don't want to add more random write any more although we don't have > a trouble of real memory shortage. > > Do you have any reason to reclaim memory urgently as writing dirty pages? > Maybe if we wait a little bit of time, flusher would write out the page. > We would like to reduce the writing dirty pages from page reclaim, especially from direct reclaim. AFAIK, the try_to_free_mem_cgroup_pages() still need to write dirty pages when there is a need. removing this from the per-memcg kswap will only add more pressure to the per-memcg direct reclaim, which seems to be worse. (stack overflow as one example which we would like to get rid of) > > > + } > > + } > > + > > + sc->nr_scanned = total_scanned; > > + return; > > unnecessary return. > > removed. > > +} > > + > > +/* > > + * Per cgroup background reclaim. > > + * TODO: Take off the order since memcg always do order 0 > > + */ > > +static unsigned long balance_mem_cgroup_pgdat(struct mem_cgroup > *mem_cont, > > + int order) > > +{ > > + int i, nid; > > + int start_node; > > + int priority; > > + bool wmark_ok; > > + int loop; > > + pg_data_t *pgdat; > > + nodemask_t do_nodes; > > + unsigned long total_scanned; > > + struct scan_control sc = { > > + .gfp_mask = GFP_KERNEL, > > + .may_unmap = 1, > > + .may_swap = 1, > > + .nr_to_reclaim = SWAP_CLUSTER_MAX, > > + .swappiness = vm_swappiness, > > + .order = order, > > + .mem_cgroup = mem_cont, > > + }; > > + > > +loop_again: > > + do_nodes = NODE_MASK_NONE; > > + sc.may_writepage = !laptop_mode; > > I think it depends on urgency(ie, priority, reclaim > ratio(#reclaim/#scanning) or something), not laptop_mode in case of > memcg. > As I said earlier,it wold be better to avoid random write. > I agree that we would like to avoid it. but not sure if we should remove it here, since it add more pressure to the direct reclaim case. > > > + sc.nr_reclaimed = 0; > > + total_scanned = 0; > > + > > + for (priority = DEF_PRIORITY; priority >= 0; priority--) { > > + sc.priority = priority; > > + wmark_ok = false; > > + loop = 0; > > + > > + /* The swap token gets in the way of swapout... */ > > + if (!priority) > > + disable_swap_token(); > > + > > + if (priority == DEF_PRIORITY) > > + do_nodes = node_states[N_ONLINE]; > > + > > + while (1) { > > + nid = mem_cgroup_select_victim_node(mem_cont, > > + &do_nodes); > > + > > + /* Indicate we have cycled the nodelist once > > Fix comment style. > Fixed. > > > + * TODO: we might add MAX_RECLAIM_LOOP for > preventing > > + * kswapd burning cpu cycles. > > + */ > > + if (loop == 0) { > > + start_node = nid; > > + loop++; > > + } else if (nid == start_node) > > + break; > > + > > + pgdat = NODE_DATA(nid); > > + balance_pgdat_node(pgdat, order, &sc); > > + total_scanned += sc.nr_scanned; > > + > > + /* Set the node which has at least > > Fix comment style. > > Fixed. > > + * one reclaimable zone > > + */ > > + for (i = pgdat->nr_zones - 1; i >= 0; i--) { > > + struct zone *zone = pgdat->node_zones + > i; > > + > > + if (!populated_zone(zone)) > > + continue; > > + } > > I can't understand your comment and logic. > The comment mentioned reclaimable zone but the logic checks just > populated_zone. What's meaning? > I will move the comment to another patch which adds the zone unreclaimable. --Ying > > > + if (i < 0) > > + node_clear(nid, do_nodes); > > + > > + if (mem_cgroup_watermark_ok(mem_cont, > > + > CHARGE_WMARK_HIGH)) { > > + wmark_ok = true; > > + goto out; > > + } > > + > > + if (nodes_empty(do_nodes)) { > > + wmark_ok = true; > > + goto out; > > + } > > + } > > + > > + if (total_scanned && priority < DEF_PRIORITY - 2) > > + congestion_wait(WRITE, HZ/10); > > + > > + if (sc.nr_reclaimed >= SWAP_CLUSTER_MAX) > > + break; > > + } > > +out: > > + if (!wmark_ok) { > > + cond_resched(); > > + > > + try_to_freeze(); > > + > > + goto loop_again; > > + } > > + > > + return sc.nr_reclaimed; > > +} > > +#else > > static unsigned long balance_mem_cgroup_pgdat(struct mem_cgroup > *mem_cont, > > int order) > > { > > return 0; > > } > > +#endif > > > > /* > > * The background pageout daemon, started as a kernel thread > > -- > > 1.7.3.1 > > > > > > > > -- > Kind regards, > Minchan Kim >