Re: [PATCH RFC] mm/madvise: implement MADV_STOCKPILE (kswapd from user space)

From: Michal Hocko
Date: Mon May 27 2019 - 10:15:42 EST

[Cc linux-api. Please always cc this list when proposing a new user
visible api. Keeping the rest of the email intact for reference]

On Mon 27-05-19 13:05:58, Konstantin Khlebnikov wrote:
> Memory cgroup has no background memory reclaimer. Reclaiming after passing
> high-limit blocks task because works synchronously in task-work.
>
> This implements manual kswapd-style memory reclaim initiated by userspace.
> It reclaims both physical memory and cgroup pages. It works in context of
> task who calls syscall madvise thus cpu time is accounted correctly.
>
> Interface:
>
> ret = madvise(ptr, size, MADV_STOCKPILE)
>
> Returns:
> 0 - ok, free memory >= size
> -EINVAL - not supported
> -ENOMEM - not enough memory/cgroup limit
> -EINTR - interrupted by pending signal
> -EAGAIN - cannot reclaim enough memory
>
> Argument 'size' is interpreted size of required free memory.
> Implementation triggers direct reclaim until amount of free memory is
> lower than that size. Argument 'ptr' could points to vma for specifying
> numa allocation policy, right now should be NULL.
>
> Usage scenario: independent thread or standalone daemon estimates rate of
> allocations and calls MADV_STOCKPILE in loop to prepare free pages.
> Thus fast path avoids allocation latency induced by direct reclaim.
>
> We are using this embedded into memory allocator based on MADV_FREE.
>
>
> Demonstration in memory cgroup with limit 1G:
>
> touch zero
> truncate -s 5G zero
>
> Without stockpile:
>
> perf stat -e vmscan:* md5sum zero
>
> Performance counter stats for 'md5sum zero':
>
> 0 vmscan:mm_vmscan_kswapd_sleep
> 0 vmscan:mm_vmscan_kswapd_wake
> 0 vmscan:mm_vmscan_wakeup_kswapd
> 0 vmscan:mm_vmscan_direct_reclaim_begin
> 10147 vmscan:mm_vmscan_memcg_reclaim_begin
> 0 vmscan:mm_vmscan_memcg_softlimit_reclaim_begin
> 0 vmscan:mm_vmscan_direct_reclaim_end
> 10147 vmscan:mm_vmscan_memcg_reclaim_end
> 0 vmscan:mm_vmscan_memcg_softlimit_reclaim_end
> 99910 vmscan:mm_shrink_slab_start
> 99910 vmscan:mm_shrink_slab_end
> 39654 vmscan:mm_vmscan_lru_isolate
> 0 vmscan:mm_vmscan_writepage
> 39652 vmscan:mm_vmscan_lru_shrink_inactive
> 2 vmscan:mm_vmscan_lru_shrink_active
> 19982 vmscan:mm_vmscan_inactive_list_is_low
>
> 10.886832585 seconds time elapsed
>
> 8.928366000 seconds user
> 1.935212000 seconds sys
>
> With stockpile:
>
> stockpile 100 10 & # up to 100M every 10ms
> perf stat -e vmscan:* md5sum zero
>
> Performance counter stats for 'md5sum zero':
>
> 0 vmscan:mm_vmscan_kswapd_sleep
> 0 vmscan:mm_vmscan_kswapd_wake
> 0 vmscan:mm_vmscan_wakeup_kswapd
> 0 vmscan:mm_vmscan_direct_reclaim_begin
> 0 vmscan:mm_vmscan_memcg_reclaim_begin
> 0 vmscan:mm_vmscan_memcg_softlimit_reclaim_begin
> 0 vmscan:mm_vmscan_direct_reclaim_end
> 0 vmscan:mm_vmscan_memcg_reclaim_end
> 0 vmscan:mm_vmscan_memcg_softlimit_reclaim_end
> 0 vmscan:mm_shrink_slab_start
> 0 vmscan:mm_shrink_slab_end
> 0 vmscan:mm_vmscan_lru_isolate
> 0 vmscan:mm_vmscan_writepage
> 0 vmscan:mm_vmscan_lru_shrink_inactive
> 0 vmscan:mm_vmscan_lru_shrink_active
> 0 vmscan:mm_vmscan_inactive_list_is_low
>
> 10.469776675 seconds time elapsed
>
> 8.976261000 seconds user
> 1.491378000 seconds sys
>
> Signed-off-by: Konstantin Khlebnikov <khlebnikov@xxxxxxxxxxxxxx>
> ---
> include/linux/memcontrol.h | 6 +++++
> include/uapi/asm-generic/mman-common.h | 2 ++
> mm/madvise.c | 39 ++++++++++++++++++++++++++++++
> mm/memcontrol.c | 41 ++++++++++++++++++++++++++++++++
> tools/vm/Makefile | 2 +-
> tools/vm/stockpile.c | 30 +++++++++++++++++++++++
> 6 files changed, 119 insertions(+), 1 deletion(-)
> create mode 100644 tools/vm/stockpile.c
>
> diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
> index bc74d6a4407c..25325f18ad55 100644
> --- a/include/linux/memcontrol.h
> +++ b/include/linux/memcontrol.h
> @@ -517,6 +517,7 @@ unsigned long mem_cgroup_get_zone_lru_size(struct lruvec *lruvec,
> }
>
> void mem_cgroup_handle_over_high(void);
> +int mem_cgroup_stockpile(unsigned long goal_pages);
>
> unsigned long mem_cgroup_get_max(struct mem_cgroup *memcg);
>
> @@ -968,6 +969,11 @@ static inline void mem_cgroup_handle_over_high(void)
> {
> }
>
> +static inline int mem_cgroup_stockpile(unsigned long goal_page)
> +{
> + return 0;
> +}
> +
> static inline void mem_cgroup_enter_user_fault(void)
> {
> }
> diff --git a/include/uapi/asm-generic/mman-common.h b/include/uapi/asm-generic/mman-common.h
> index abd238d0f7a4..675145864fee 100644
> --- a/include/uapi/asm-generic/mman-common.h
> +++ b/include/uapi/asm-generic/mman-common.h
> @@ -64,6 +64,8 @@
> #define MADV_WIPEONFORK 18 /* Zero memory on fork, child only */
> #define MADV_KEEPONFORK 19 /* Undo MADV_WIPEONFORK */
>
> +#define MADV_STOCKPILE 20 /* stockpile free pages */
> +
> /* compatibility flags */
> #define MAP_FILE 0
>
> diff --git a/mm/madvise.c b/mm/madvise.c
> index 628022e674a7..f908b08ecc9f 100644
> --- a/mm/madvise.c
> +++ b/mm/madvise.c
> @@ -686,6 +686,41 @@ static int madvise_inject_error(int behavior,
> }
> #endif
>
> +static long madvise_stockpile(unsigned long start, size_t len)
> +{
> + unsigned long goal_pages, progress;
> + struct zonelist *zonelist;
> + int ret;
> +
> + if (start)
> + return -EINVAL;
> +
> + goal_pages = len >> PAGE_SHIFT;
> +
> + if (goal_pages > totalram_pages() - totalreserve_pages)
> + return -ENOMEM;
> +
> + ret = mem_cgroup_stockpile(goal_pages);
> + if (ret)
> + return ret;
> +
> + /* TODO: use vma mempolicy */
> + zonelist = node_zonelist(numa_node_id(), GFP_HIGHUSER);
> +
> + while (global_zone_page_state(NR_FREE_PAGES) <
> + goal_pages + totalreserve_pages) {
> +
> + if (signal_pending(current))
> + return -EINTR;
> +
> + progress = try_to_free_pages(zonelist, 0, GFP_HIGHUSER, NULL);
> + if (!progress)
> + return -EAGAIN;
> + }
> +
> + return 0;
> +}
> +
> static long
> madvise_vma(struct vm_area_struct *vma, struct vm_area_struct **prev,
> unsigned long start, unsigned long end, int behavior)
> @@ -728,6 +763,7 @@ madvise_behavior_valid(int behavior)
> case MADV_DODUMP:
> case MADV_WIPEONFORK:
> case MADV_KEEPONFORK:
> + case MADV_STOCKPILE:
> #ifdef CONFIG_MEMORY_FAILURE
> case MADV_SOFT_OFFLINE:
> case MADV_HWPOISON:
> @@ -834,6 +870,9 @@ SYSCALL_DEFINE3(madvise, unsigned long, start, size_t, len_in, int, behavior)
> return madvise_inject_error(behavior, start, start + len_in);
> #endif
>
> + if (behavior == MADV_STOCKPILE)
> + return madvise_stockpile(start, len);
> +
> write = madvise_need_mmap_write(behavior);
> if (write) {
> if (down_write_killable(&current->mm->mmap_sem))
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index e50a2db5b4ff..dc23dc6bbeb3 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -2276,6 +2276,47 @@ void mem_cgroup_handle_over_high(void)
> current->memcg_nr_pages_over_high = 0;
> }
>
> +int mem_cgroup_stockpile(unsigned long goal_pages)
> +{
> + int nr_retries = MEM_CGROUP_RECLAIM_RETRIES;
> + unsigned long limit, nr_free, progress;
> + struct mem_cgroup *memcg, *pos;
> + int ret = 0;
> +
> + pos = memcg = get_mem_cgroup_from_mm(current->mm);
> +
> +retry:
> + if (signal_pending(current)) {
> + ret = -EINTR;
> + goto out;
> + }
> +
> + limit = min(pos->memory.max, pos->high);
> + if (goal_pages > limit) {
> + ret = -ENOMEM;
> + goto out;
> + }
> +
> + nr_free = limit - page_counter_read(&pos->memory);
> + if ((long)nr_free < (long)goal_pages) {
> + progress = try_to_free_mem_cgroup_pages(pos,
> + goal_pages - nr_free, GFP_HIGHUSER, true);
> + if (progress || nr_retries--)
> + goto retry;
> + ret = -EAGAIN;
> + goto out;
> + }
> +
> + nr_retries = MEM_CGROUP_RECLAIM_RETRIES;
> + pos = parent_mem_cgroup(pos);
> + if (pos)
> + goto retry;
> +
> +out:
> + css_put(&memcg->css);
> + return ret;
> +}
> +
> static int try_charge(struct mem_cgroup *memcg, gfp_t gfp_mask,
> unsigned int nr_pages)
> {
> diff --git a/tools/vm/Makefile b/tools/vm/Makefile
> index 20f6cf04377f..e5b5bc0d9421 100644
> --- a/tools/vm/Makefile
> +++ b/tools/vm/Makefile
> @@ -1,7 +1,7 @@
> # SPDX-License-Identifier: GPL-2.0
> # Makefile for vm tools
> #
> -TARGETS=page-types slabinfo page_owner_sort
> +TARGETS=page-types slabinfo page_owner_sort stockpile
>
> LIB_DIR = ../lib/api
> LIBS = $(LIB_DIR)/libapi.a
> diff --git a/tools/vm/stockpile.c b/tools/vm/stockpile.c
> new file mode 100644
> index 000000000000..245e24f293ec
> --- /dev/null
> +++ b/tools/vm/stockpile.c
> @@ -0,0 +1,30 @@
> +// SPDX-License-Identifier: GPL-2.0
> +#include <sys/mman.h>
> +#include <stdlib.h>
> +#include <unistd.h>
> +#include <err.h>
> +#include <errno.h>
> +
> +#ifndef MADV_STOCKPILE
> +# define MADV_STOCKPILE 20
> +#endif
> +
> +int main(int argc, char **argv)
> +{
> + int interval;
> + size_t size;
> + int ret;
> +
> + if (argc != 3)
> + errx(1, "usage: %s <size_mb> <interval_ms>", argv[0]);
> +
> + size = atol(argv[1]) << 20;
> + interval = atoi(argv[2]) * 1000;
> +
> + while (1) {
> + ret = madvise(NULL, size, MADV_STOCKPILE);
> + if (ret && errno != EAGAIN)
> + err(2, "madvise(NULL, %zu, MADV_STOCKPILE)", size);
> + usleep(interval);
> + }
> +}
>

--
Michal Hocko
SUSE Labs