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Message-ID: <Y4i+6bjLGy/GF7uM@dhcp22.suse.cz>
Date: Thu, 1 Dec 2022 15:49:13 +0100
From: Michal Hocko <mhocko@...e.com>
To: Mina Almasry <almasrymina@...gle.com>
Cc: Huang Ying <ying.huang@...el.com>,
Yang Shi <yang.shi@...ux.alibaba.com>,
Yosry Ahmed <yosryahmed@...gle.com>,
Tim Chen <tim.c.chen@...ux.intel.com>, weixugc@...gle.com,
shakeelb@...gle.com, gthelen@...gle.com, fvdl@...gle.com,
Tejun Heo <tj@...nel.org>, Zefan Li <lizefan.x@...edance.com>,
Johannes Weiner <hannes@...xchg.org>,
Jonathan Corbet <corbet@....net>,
Roman Gushchin <roman.gushchin@...ux.dev>,
Muchun Song <songmuchun@...edance.com>,
Andrew Morton <akpm@...ux-foundation.org>,
cgroups@...r.kernel.org, linux-doc@...r.kernel.org,
linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [RFC PATCH v2] mm: Add nodes= arg to memory.reclaim
On Tue 29-11-22 18:03:27, Mina Almasry wrote:
> The nodes= arg instructs the kernel to only scan the given nodes for
> proactive reclaim. For example use cases, consider a 2 tier memory system:
>
> nodes 0,1 -> top tier
> nodes 2,3 -> second tier
>
> $ echo "1m nodes=0" > memory.reclaim
>
> This instructs the kernel to attempt to reclaim 1m memory from node 0.
> Since node 0 is a top tier node, demotion will be attempted first. This
> is useful to direct proactive reclaim to specific nodes that are under
> pressure.
>
> $ echo "1m nodes=2,3" > memory.reclaim
>
> This instructs the kernel to attempt to reclaim 1m memory in the second tier,
> since this tier of memory has no demotion targets the memory will be
> reclaimed.
>
> $ echo "1m nodes=0,1" > memory.reclaim
>
> Instructs the kernel to reclaim memory from the top tier nodes, which can
> be desirable according to the userspace policy if there is pressure on
> the top tiers. Since these nodes have demotion targets, the kernel will
> attempt demotion first.
>
> Since commit 3f1509c57b1b ("Revert "mm/vmscan: never demote for memcg
> reclaim""), the proactive reclaim interface memory.reclaim does both
> reclaim and demotion. Reclaim and demotion incur different latency costs
> to the jobs in the cgroup. Demoted memory would still be addressable
> by the userspace at a higher latency, but reclaimed memory would need to
> incur a pagefault.
>
> The 'nodes' arg is useful to allow the userspace to control demotion
> and reclaim independently according to its policy: if the memory.reclaim
> is called on a node with demotion targets, it will attempt demotion first;
> if it is called on a node without demotion targets, it will only attempt
> reclaim.
>
> Signed-off-by: Mina Almasry <almasrymina@...gle.com>
Thanks for making this per node rather than tier based. This is a more
generic interface.
Acked-by: Michal Hocko <mhocko@...e.com>
Thanks!
> ---
> Documentation/admin-guide/cgroup-v2.rst | 15 +++---
> include/linux/swap.h | 3 +-
> mm/memcontrol.c | 67 ++++++++++++++++++++-----
> mm/vmscan.c | 4 +-
> 4 files changed, 68 insertions(+), 21 deletions(-)
>
> diff --git a/Documentation/admin-guide/cgroup-v2.rst b/Documentation/admin-guide/cgroup-v2.rst
> index 74cec76be9f2..ac5fcbcd5ae6 100644
> --- a/Documentation/admin-guide/cgroup-v2.rst
> +++ b/Documentation/admin-guide/cgroup-v2.rst
> @@ -1245,17 +1245,13 @@ PAGE_SIZE multiple when read back.
> This is a simple interface to trigger memory reclaim in the
> target cgroup.
>
> - This file accepts a single key, the number of bytes to reclaim.
> - No nested keys are currently supported.
> + This file accepts a string which contains the number of bytes to
> + reclaim.
>
> Example::
>
> echo "1G" > memory.reclaim
>
> - The interface can be later extended with nested keys to
> - configure the reclaim behavior. For example, specify the
> - type of memory to reclaim from (anon, file, ..).
> -
> Please note that the kernel can over or under reclaim from
> the target cgroup. If less bytes are reclaimed than the
> specified amount, -EAGAIN is returned.
> @@ -1267,6 +1263,13 @@ PAGE_SIZE multiple when read back.
> This means that the networking layer will not adapt based on
> reclaim induced by memory.reclaim.
>
> + This file also allows the user to specify the nodes to reclaim from,
> + via the 'nodes=' key, example::
> +
> + echo "1G nodes=0,1" > memory.reclaim
> +
> + The above instructs the kernel to reclaim memory from nodes 0,1.
> +
> memory.peak
> A read-only single value file which exists on non-root
> cgroups.
> diff --git a/include/linux/swap.h b/include/linux/swap.h
> index b61e2007d156..f542c114dffd 100644
> --- a/include/linux/swap.h
> +++ b/include/linux/swap.h
> @@ -419,7 +419,8 @@ 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,
> + nodemask_t nodemask);
> 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 23750cec0036..a0d7850173a9 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 "internal.h"
> #include <net/sock.h>
> #include <net/ip.h>
> @@ -2392,7 +2393,8 @@ 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,
> + NODE_MASK_ALL);
> psi_memstall_leave(&pflags);
> } while ((memcg = parent_mem_cgroup(memcg)) &&
> !mem_cgroup_is_root(memcg));
> @@ -2683,7 +2685,8 @@ 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,
> + NODE_MASK_ALL);
> psi_memstall_leave(&pflags);
>
> if (mem_cgroup_margin(mem_over_limit) >= nr_pages)
> @@ -3503,7 +3506,8 @@ 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,
> + NODE_MASK_ALL)) {
> ret = -EBUSY;
> break;
> }
> @@ -3614,7 +3618,8 @@ 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,
> + NODE_MASK_ALL))
> nr_retries--;
> }
>
> @@ -6407,7 +6412,8 @@ 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,
> + NODE_MASK_ALL);
>
> if (!reclaimed && !nr_retries--)
> break;
> @@ -6456,7 +6462,8 @@ 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,
> + NODE_MASK_ALL))
> nr_reclaims--;
> continue;
> }
> @@ -6579,21 +6586,54 @@ static ssize_t memory_oom_group_write(struct kernfs_open_file *of,
> return nbytes;
> }
>
> +enum {
> + MEMORY_RECLAIM_NODES = 0,
> + MEMORY_RECLAIM_NULL,
> +};
> +
> +static const match_table_t if_tokens = {
> + { MEMORY_RECLAIM_NODES, "nodes=%s" },
> + { MEMORY_RECLAIM_NULL, NULL },
> +};
> +
> static ssize_t memory_reclaim(struct kernfs_open_file *of, char *buf,
> size_t nbytes, loff_t off)
> {
> struct mem_cgroup *memcg = mem_cgroup_from_css(of_css(of));
> unsigned int nr_retries = MAX_RECLAIM_RETRIES;
> unsigned long nr_to_reclaim, nr_reclaimed = 0;
> - unsigned int reclaim_options;
> - int err;
> + unsigned int reclaim_options = MEMCG_RECLAIM_MAY_SWAP |
> + MEMCG_RECLAIM_PROACTIVE;
> + char *old_buf, *start;
> + substring_t args[MAX_OPT_ARGS];
> + int token;
> + char value[256];
> + nodemask_t nodemask = NODE_MASK_ALL;
>
> buf = strstrip(buf);
> - err = page_counter_memparse(buf, "", &nr_to_reclaim);
> - if (err)
> - return err;
>
> - reclaim_options = MEMCG_RECLAIM_MAY_SWAP | MEMCG_RECLAIM_PROACTIVE;
> + 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;
> + token = match_token(start, if_tokens, args);
> + match_strlcpy(value, args, sizeof(value));
> + switch (token) {
> + case MEMORY_RECLAIM_NODES:
> + if (nodelist_parse(value, nodemask) < 0)
> + return -EINVAL;
> + break;
> + default:
> + return -EINVAL;
> + }
> + }
> +
> while (nr_reclaimed < nr_to_reclaim) {
> unsigned long reclaimed;
>
> @@ -6610,7 +6650,8 @@ static ssize_t memory_reclaim(struct kernfs_open_file *of, char *buf,
>
> reclaimed = try_to_free_mem_cgroup_pages(memcg,
> nr_to_reclaim - nr_reclaimed,
> - GFP_KERNEL, reclaim_options);
> + GFP_KERNEL, reclaim_options,
> + nodemask);
>
> if (!reclaimed && !nr_retries--)
> return -EAGAIN;
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 7b8e8e43806b..23fc5b523764 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -6735,7 +6735,8 @@ 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,
> + nodemask_t nodemask)
> {
> unsigned long nr_reclaimed;
> unsigned int noreclaim_flag;
> @@ -6750,6 +6751,7 @@ 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),
> + .nodemask = &nodemask,
> };
> /*
> * Traverse the ZONELIST_FALLBACK zonelist of the current node to put
> --
> 2.38.1.584.g0f3c55d4c2-goog
--
Michal Hocko
SUSE Labs
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