[PATCH 1/1] mm: add swapiness= arg to memory.reclaim

Dan Schatzberg
2023-11-30T15:38:29Z

Allow proactive reclaimers to submit an additional swappiness=<val>
argument to memory.reclaim. This overrides the global or per-memcg
swappiness setting for that reclaim attempt.

For example:

echo "2M swappiness=0" > /sys/fs/cgroup/memory.reclaim

will perform reclaim on the rootcg with a swappiness setting of 0 (no
swap) regardless of the vm.swappiness sysctl setting.

Signed-off-by: Dan Schatzberg <schatzberg.dan@gmail.com>
---
include/linux/swap.h | 3 ++-
mm/memcontrol.c | 55 +++++++++++++++++++++++++++++++++++---------
mm/vmscan.c | 13 +++++++++--
3 files changed, 57 insertions(+), 14 deletions(-)

diff --git a/include/linux/swap.h b/include/linux/swap.h
index f6dd6575b905..c6e309199f10 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -410,7 +410,8 @@ extern unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
extern unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *memcg,
unsigned long nr_pages,
gfp_t gfp_mask,
- unsigned int reclaim_options);
+ unsigned int reclaim_options,
+ int *swappiness);
extern unsigned long mem_cgroup_shrink_node(struct mem_cgroup *mem,
gfp_t gfp_mask, bool noswap,
pg_data_t *pgdat,
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 1c1061df9cd1..ba1c89455ab0 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -63,6 +63,7 @@
#include <linux/resume_user_mode.h>
#include <linux/psi.h>
#include <linux/seq_buf.h>
+#include <linux/parser.h>
#include <linux/sched/isolation.h>
#include "internal.h"
#include <net/sock.h>
@@ -2449,7 +2450,7 @@ static unsigned long reclaim_high(struct mem_cgroup *memcg,
psi_memstall_enter(&pflags);
nr_reclaimed += try_to_free_mem_cgroup_pages(memcg, nr_pages,
gfp_mask,
- MEMCG_RECLAIM_MAY_SWAP);
+ MEMCG_RECLAIM_MAY_SWAP, NULL);
psi_memstall_leave(&pflags);
} while ((memcg = parent_mem_cgroup(memcg)) &&
!mem_cgroup_is_root(memcg));
@@ -2740,7 +2741,7 @@ static int try_charge_memcg(struct mem_cgroup *memcg, gfp_t gfp_mask,

psi_memstall_enter(&pflags);
nr_reclaimed = try_to_free_mem_cgroup_pages(mem_over_limit, nr_pages,
- gfp_mask, reclaim_options);
+ gfp_mask, reclaim_options, NULL);
psi_memstall_leave(&pflags);

if (mem_cgroup_margin(mem_over_limit) >= nr_pages)
@@ -3660,7 +3661,7 @@ static int mem_cgroup_resize_max(struct mem_cgroup *memcg,
}

if (!try_to_free_mem_cgroup_pages(memcg, 1, GFP_KERNEL,
- memsw ? 0 : MEMCG_RECLAIM_MAY_SWAP)) {
+ memsw ? 0 : MEMCG_RECLAIM_MAY_SWAP, NULL)) {
ret = -EBUSY;
break;
}
@@ -3774,7 +3775,7 @@ static int mem_cgroup_force_empty(struct mem_cgroup *memcg)
return -EINTR;

if (!try_to_free_mem_cgroup_pages(memcg, 1, GFP_KERNEL,
- MEMCG_RECLAIM_MAY_SWAP))
+ MEMCG_RECLAIM_MAY_SWAP, NULL))
nr_retries--;
}

@@ -6720,7 +6721,7 @@ static ssize_t memory_high_write(struct kernfs_open_file *of,
}

reclaimed = try_to_free_mem_cgroup_pages(memcg, nr_pages - high,
- GFP_KERNEL, MEMCG_RECLAIM_MAY_SWAP);
+ GFP_KERNEL, MEMCG_RECLAIM_MAY_SWAP, NULL);

if (!reclaimed && !nr_retries--)
break;
@@ -6769,7 +6770,7 @@ static ssize_t memory_max_write(struct kernfs_open_file *of,

if (nr_reclaims) {
if (!try_to_free_mem_cgroup_pages(memcg, nr_pages - max,
- GFP_KERNEL, MEMCG_RECLAIM_MAY_SWAP))
+ GFP_KERNEL, MEMCG_RECLAIM_MAY_SWAP, NULL))
nr_reclaims--;
continue;
}
@@ -6895,6 +6896,16 @@ static ssize_t memory_oom_group_write(struct kernfs_open_file *of,
return nbytes;
}

+enum {
+ MEMORY_RECLAIM_SWAPPINESS = 0,
+ MEMORY_RECLAIM_NULL,
+};
+
+static const match_table_t if_tokens = {
+ { MEMORY_RECLAIM_SWAPPINESS, "swappiness=%d"},
+ { MEMORY_RECLAIM_NULL, NULL },
+};
+
static ssize_t memory_reclaim(struct kernfs_open_file *of, char *buf,
size_t nbytes, loff_t off)
{
@@ -6902,12 +6913,33 @@ static ssize_t memory_reclaim(struct kernfs_open_file *of, char *buf,
unsigned int nr_retries = MAX_RECLAIM_RETRIES;
unsigned long nr_to_reclaim, nr_reclaimed = 0;
unsigned int reclaim_options;
- int err;
+ char *old_buf, *start;
+ substring_t args[MAX_OPT_ARGS];
+ int swappiness = -1;

buf = strstrip(buf);
- err = page_counter_memparse(buf, "", &nr_to_reclaim);
- if (err)
- return err;
+
+ old_buf = buf;
+ nr_to_reclaim = memparse(buf, &buf) / PAGE_SIZE;
+ if (buf == old_buf)
+ return -EINVAL;
+
+ buf = strstrip(buf);
+
+ while ((start = strsep(&buf, " ")) != NULL) {
+ if (!strlen(start))
+ continue;
+ switch (match_token(start, if_tokens, args)) {
+ case MEMORY_RECLAIM_SWAPPINESS:
+ if (match_int(&args[0], &swappiness))
+ return -EINVAL;
+ if (swappiness < 0 || swappiness > 200)
+ return -EINVAL;
+ break;
+ default:
+ return -EINVAL;
+ }
+ }

reclaim_options = MEMCG_RECLAIM_MAY_SWAP | MEMCG_RECLAIM_PROACTIVE;
while (nr_reclaimed < nr_to_reclaim) {
@@ -6926,7 +6958,8 @@ static ssize_t memory_reclaim(struct kernfs_open_file *of, char *buf,

reclaimed = try_to_free_mem_cgroup_pages(memcg,
min(nr_to_reclaim - nr_reclaimed, SWAP_CLUSTER_MAX),
- GFP_KERNEL, reclaim_options);
+ GFP_KERNEL, reclaim_options,
+ swappiness == -1 ? NULL : &swappiness);

if (!reclaimed && !nr_retries--)
return -EAGAIN;
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 506f8220c5fe..546704ea01e1 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -136,6 +136,9 @@ struct scan_control {
/* Always discard instead of demoting to lower tier memory */
unsigned int no_demotion:1;

+ /* Swappiness value for reclaim, if NULL use memcg/global value */
+ int *swappiness;
+
/* Allocation order */
s8 order;

@@ -2327,7 +2330,8 @@ static void get_scan_count(struct lruvec *lruvec, struct scan_control *sc,
struct pglist_data *pgdat = lruvec_pgdat(lruvec);
struct mem_cgroup *memcg = lruvec_memcg(lruvec);
unsigned long anon_cost, file_cost, total_cost;
- int swappiness = mem_cgroup_swappiness(memcg);
+ int swappiness = sc->swappiness ?
+ *sc->swappiness : mem_cgroup_swappiness(memcg);
u64 fraction[ANON_AND_FILE];
u64 denominator = 0; /* gcc */
enum scan_balance scan_balance;
@@ -2608,6 +2612,9 @@ static int get_swappiness(struct lruvec *lruvec, struct scan_control *sc)
mem_cgroup_get_nr_swap_pages(memcg) < MIN_LRU_BATCH)
return 0;

+ if (sc->swappiness)
+ return *sc->swappiness;
+
return mem_cgroup_swappiness(memcg);
}

@@ -6433,7 +6440,8 @@ unsigned long mem_cgroup_shrink_node(struct mem_cgroup *memcg,
unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *memcg,
unsigned long nr_pages,
gfp_t gfp_mask,
- unsigned int reclaim_options)
+ unsigned int reclaim_options,
+ int *swappiness)
{
unsigned long nr_reclaimed;
unsigned int noreclaim_flag;
@@ -6448,6 +6456,7 @@ unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *memcg,
.may_unmap = 1,
.may_swap = !!(reclaim_options & MEMCG_RECLAIM_MAY_SWAP),
.proactive = !!(reclaim_options & MEMCG_RECLAIM_PROACTIVE),
+ .swappiness = swappiness,
};
/*
* Traverse the ZONELIST_FALLBACK zonelist of the current node to put
--
2.34.1