On Thu, Apr 14, 2011 at 6:11 PM, KAMEZAWA Hiroyuki < kamezawa.hiroyu@jp.fujitsu.com> wrote: > On Thu, 14 Apr 2011 15:54:25 -0700 > 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 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 | 161 > +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ > > 1 files changed, 161 insertions(+), 0 deletions(-) > > > > diff --git a/mm/vmscan.c b/mm/vmscan.c > > index 4deb9c8..b8345d2 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)) > > @@ -2632,11 +2636,168 @@ 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; > > + > > + /* > > + * Now scan the zone in the dma->highmem direction, and we scan > > + * every zones for each node. > > + * > > + * We do this because the page allocator works in the opposite > > + * direction. This prevents the page allocator from allocating > > + * pages behind kswapd's direction of progress, which would > > + * cause too much scanning of the lower zones. > > + */ > > I guess this comment is a cut-n-paste from global kswapd. It works when > alloc_page() stalls....hmm, I'd like to think whether dma->highmem > direction > is good in this case. > This is a legacy comment and the actual logic of zone balancing has been removed from this patch. > > As you know, memcg works against user's memory, memory should be in highmem > zone. > Memcg-kswapd is not for memory-shortage, but for voluntary page dropping by > _user_. > in some sense, yes. but it would also related to memory-shortage on fully packed machines. > > If this memcg-kswapd drops pages from lower zones first, ah, ok, it's good > for > the system because memcg's pages should be on higher zone if we have free > memory. > > So, I think the reason for dma->highmem is different from global kswapd. > yes. I agree that the logic of dma->highmem ordering is not exactly the same from per-memcg kswapd and per-node kswapd. But still the page allocation happens on the other side, and this is still good for the system as you pointed out. > > > > > > + for (i = 0; i < pgdat->nr_zones; i++) { > > + struct zone *zone = pgdat->node_zones + i; > > + > > + if (!populated_zone(zone)) > > + continue; > > + > > + 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; > > + } > > + } > > + > > + sc->nr_scanned = total_scanned; > > + return; > > +} > > + > > +/* > > + * 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 = ULONG_MAX, > > + .swappiness = vm_swappiness, > > + .order = order, > > + .mem_cgroup = mem_cont, > > + }; > > + > > +loop_again: > > + do_nodes = NODE_MASK_NONE; > > + sc.may_writepage = !laptop_mode; > > I think may_writepage should start from '0' always. We're not sure > the system is in memory shortage...we just want to release memory > volunatary. write_page will add huge costs, I guess. > > For exmaple, > sc.may_writepage = !!loop > may be better for memcg. > > BTW, you set nr_to_reclaim as ULONG_MAX here and doesn't modify it later. > > I think you should add some logic to fix it to right value. > > For example, before calling shrink_zone(), > > sc->nr_to_reclaim = min(SWAP_CLUSETR_MAX, memcg_usage_in_this_zone() / > 100); # 1% in this zone. > > if we love 'fair pressure for each zone'. > Hmm. I don't get it. Leaving the nr_to_reclaim to be ULONG_MAX in kswapd case which is intended to add equal memory pressure for each zone. So in the shrink_zone, we won't bail out in the following condition: >-------while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_FILE] || > >------->------->------->------->-------nr[LRU_INACTIVE_FILE]) { > >------->-------if (nr_reclaimed >= nr_to_reclaim && priority < DEF_PRIORITY) >------->------->-------break; } > > --Ying > > > > > > + 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 > > + * 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 > > + * one reclaimable zone > > + */ > > + for (i = pgdat->nr_zones - 1; i >= 0; i--) { > > + struct zone *zone = pgdat->node_zones + i; > > + > > + if (!populated_zone(zone)) > > + continue; > > How about checking whether memcg has pages on this node ? > > > + } > > + 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; > > + } > > + } > > + > > + /* All the nodes are unreclaimable, kswapd is done */ > > + if (nodes_empty(do_nodes)) { > > + wmark_ok = true; > > + goto out; > > + } > > Can this happen ? > > > > + > > + 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 > > > > > Thanks, > -Kame > >