> 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 v7..v6:
> 1. change based on KAMAZAWA's patchset. Each memcg reclaims now reclaims
> SWAP_CLUSTER_MAX of pages and putback the memcg to the tail of list.
> memcg-kswapd will visit memcgs in round-robin manner and reduce usages.
>
> changelog v6..v5:
> 1. add mem_cgroup_zone_reclaimable_pages()
> 2. fix some comment style.
>
> 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.
>
> 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 <yinghan@xxxxxxxxxx>
> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
> ---
> include/linux/memcontrol.h | 9 +++
> mm/memcontrol.c | 18 +++++++
> mm/vmscan.c | 118 ++++++++++++++++++++++++++++++++++++++++++++
> 3 files changed, 145 insertions(+), 0 deletions(-)
>
> diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
> index 7444738..39eade6 100644
> --- a/include/linux/memcontrol.h
> +++ b/include/linux/memcontrol.h
> @@ -115,6 +115,8 @@ extern void mem_cgroup_end_migration(struct mem_cgroup *mem,
> */
> int mem_cgroup_inactive_anon_is_low(struct mem_cgroup *memcg);
> int mem_cgroup_inactive_file_is_low(struct mem_cgroup *memcg);
> +unsigned long mem_cgroup_zone_reclaimable_pages(struct mem_cgroup *memcg,
> + struct zone *zone);
> unsigned long mem_cgroup_zone_nr_pages(struct mem_cgroup *memcg,
> struct zone *zone,
> enum lru_list lru);
> @@ -311,6 +313,13 @@ mem_cgroup_inactive_file_is_low(struct mem_cgroup *memcg)
> }
>
> static inline unsigned long
> +mem_cgroup_zone_reclaimable_pages(struct mem_cgroup *memcg,
> + struct zone *zone)
> +{
> + return 0;
> +}
> +
> +static inline unsigned long
> mem_cgroup_zone_nr_pages(struct mem_cgroup *memcg, struct zone *zone,
> enum lru_list lru)
> {
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 4696fd8..41eaa62 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -1105,6 +1105,24 @@ int mem_cgroup_inactive_file_is_low(struct mem_cgroup *memcg)
> return (active > inactive);
> }
>
> +unsigned long mem_cgroup_zone_reclaimable_pages(struct mem_cgroup *memcg,
> + struct zone *zone)
> +{
> + int nr;
> + int nid = zone_to_nid(zone);
> + int zid = zone_idx(zone);
> + struct mem_cgroup_per_zone *mz = mem_cgroup_zoneinfo(memcg, nid, zid);
> +
> + nr = MEM_CGROUP_ZSTAT(mz, NR_ACTIVE_FILE) +
> + MEM_CGROUP_ZSTAT(mz, NR_INACTIVE_FILE);
> +
> + if (nr_swap_pages > 0)
> + nr += MEM_CGROUP_ZSTAT(mz, NR_ACTIVE_ANON) +
> + MEM_CGROUP_ZSTAT(mz, NR_INACTIVE_ANON);
> +
> + return nr;
> +}
> +
> unsigned long mem_cgroup_zone_nr_pages(struct mem_cgroup *memcg,
> struct zone *zone,
> enum lru_list lru)
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 63c557e..ba03a10 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -47,6 +47,8 @@
>
> #include <linux/swapops.h>
>
> +#include <linux/res_counter.h>
> +
> #include "internal.h"
>
> #define CREATE_TRACE_POINTS
> @@ -111,6 +113,8 @@ struct scan_control {
> * are scanned.
> */
> nodemask_t *nodemask;
> +
> + int priority;
> };
Bah!
If you need sc.priority, you have to make cleanup patch at first. and
all current reclaim path have to use sc.priority. Please don't increase
unnecessary mess.
>
> #define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru))
> @@ -2620,10 +2624,124 @@ 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 shrink_memcg_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;
unnecessary local variables. we can keep smaller stack.
> +
> + /*
> + * 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;
> +
> + scan = mem_cgroup_zone_reclaimable_pages(mem_cont, zone);
> + if (!scan)
> + 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;
please make helper function for may_writepage. iow, don't cut-n-paste.
> +/*
> + * Per cgroup background reclaim.
> + * TODO: Take off the order since memcg always do order 0
> + */
> +static unsigned long shrink_mem_cgroup(struct mem_cgroup *mem_cont, int order)
> +{
> + int i, nid, priority, 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,
No. memcg has per-memcg swappiness. Please don't use global swappiness value.
> + .order = order,
> + .mem_cgroup = mem_cont,
> + };
> +
> + do_nodes = NODE_MASK_NONE;
> + sc.may_writepage = !laptop_mode;
> + sc.nr_reclaimed = 0;
this initialization move into sc static initializer. balance pgdat has
loop_again label and this doesn't.
> + total_scanned = 0;
> +
> + do_nodes = node_states[N_ONLINE];
Why do we need care memoryless node? N_HIGH_MEMORY is wrong?
> +
> + for (priority = DEF_PRIORITY;
> + (priority >= 0) && (sc.nr_to_reclaim > sc.nr_reclaimed);
> + priority--) {
bah. bad coding style...
> +
> + sc.priority = priority;
> + /* The swap token gets in the way of swapout... */
> + if (!priority)
> + disable_swap_token();
Why?
disable swap token mean "Please devest swap preventation privilege from
owner task. Instead we endure swap storm and performance hit".
However I doublt memcg memory shortage is good situation to make swap storm.
> +
> + for (loop = num_online_nodes();
> + (loop > 0) && !nodes_empty(do_nodes);
> + loop--) {
Why don't you use for_each_online_node()?
Maybe for_each_node_state(n, N_HIGH_MEMORY) is best option?
At least, find_next_bit() is efficient than bare loop?
> +
> + nid = mem_cgroup_select_victim_node(mem_cont,
> + &do_nodes);
> +
> + pgdat = NODE_DATA(nid);
> + shrink_memcg_node(pgdat, order, &sc);
> + total_scanned += sc.nr_scanned;
> +
> + for (i = pgdat->nr_zones - 1; i >= 0; i--) {
> + struct zone *zone = pgdat->node_zones + i;
> +
> + if (populated_zone(zone))
> + break;
> + }
memory less node check is here. but we can check it before.
> + if (i < 0)
> + node_clear(nid, do_nodes);
> +
> + if (mem_cgroup_watermark_ok(mem_cont,
> + CHARGE_WMARK_HIGH))
> + goto out;
> + }
> +
> + if (total_scanned && priority < DEF_PRIORITY - 2)
> + congestion_wait(WRITE, HZ/10);
> + }
> +out:
> + return sc.nr_reclaimed;
> +}
> +#else
> static unsigned long shrink_mem_cgroup(struct mem_cgroup *mem_cont, int order)
> {
> return 0;
> }
> +#endif
>
> /*
> * The background pageout daemon, started as a kernel thread
> --
> 1.7.3.1
>
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