Re: [PATCH] mm, memcg: cg2 memory{.swap,}.peak write handlers

On Mon 04-12-23 14:41:56, David Finkel wrote:

Other mechanisms for querying the peak memory usage of either a process or v1 memory cgroup allow for resetting the high watermark. Restore parity with those mechanisms.

For example:

• Any write to memory.max_usage_in_bytes in a cgroup v1 mount resets the high watermark.
• writing "5" to the clear_refs pseudo-file in a processes's proc directory resets the peak RSS.

This change copies the cgroup v1 behavior so any write to the memory.peak and memory.swap.peak pseudo-files reset the high watermark to the current usage.

This behavior is particularly useful for work scheduling systems that need to track memory usage of worker processes/cgroups per-work-item. Since memory can't be squeezed like CPU can (the OOM-killer has opinions), these systems need to track the peak memory usage to compute system/container fullness when binpacking workitems.

I do not understand the OOM-killer reference here but I do understand that your worker reuses a cgroup and you want a peak memory consumption of a single run to better profile/configure the memcg configuration for the specific worker type. Correct?

Signed-off-by: David Finkel davidf@vimeo.com

Makes sense to me Acked-by: Michal Hocko mhocko@suse.com

Thanks!

---

Documentation/admin-guide/cgroup-v2.rst | 20 +++--- mm/memcontrol.c | 23 ++++++ .../selftests/cgroup/test_memcontrol.c | 72 ++++++++++++++++--- 3 files changed, 99 insertions(+), 16 deletions(-)

diff --git a/Documentation/admin-guide/cgroup-v2.rst b/Documentation/admin-guide/cgroup-v2.rst index 3f85254f3cef..95af0628dc44 100644 --- a/Documentation/admin-guide/cgroup-v2.rst +++ b/Documentation/admin-guide/cgroup-v2.rst @@ -1305,11 +1305,13 @@ PAGE_SIZE multiple when read back. reclaim induced by memory.reclaim. memory.peak

• A read-only single value file which exists on non-root
• cgroups.

• A read-write single value file which exists on non-root cgroups.
• The max memory usage recorded for the cgroup and its descendants since
• either the creation of the cgroup or the most recent reset.

• The max memory usage recorded for the cgroup and its
• descendants since the creation of the cgroup.

• Any non-empty write to this file resets it to the current memory usage.
• All content written is completely ignored.

memory.oom.group A read-write single value file which exists on non-root @@ -1626,11 +1628,13 @@ PAGE_SIZE multiple when read back. Healthy workloads are not expected to reach this limit. memory.swap.peak

• A read-only single value file which exists on non-root
• cgroups.

• A read-write single value file which exists on non-root cgroups.
• The max swap usage recorded for the cgroup and its descendants since
• the creation of the cgroup or the most recent reset.

• The max swap usage recorded for the cgroup and its
• descendants since the creation of the cgroup.

• Any non-empty write to this file resets it to the current swap usage.
• All content written is completely ignored.

memory.swap.max A read-write single value file which exists on non-root diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 1c1061df9cd1..b04af158922d 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -25,6 +25,7 @@

• Copyright (C) 2020 Alibaba, Inc, Alex Shi

*/ +#include <linux/cgroup-defs.h> #include <linux/page_counter.h> #include <linux/memcontrol.h> #include <linux/cgroup.h> @@ -6635,6 +6636,16 @@ static u64 memory_peak_read(struct cgroup_subsys_state *css, return (u64)memcg->memory.watermark * PAGE_SIZE; } +static ssize_t memory_peak_write(struct kernfs_open_file *of,

• 		 char *buf, size_t nbytes, loff_t off)
  

+{

• struct mem_cgroup *memcg = mem_cgroup_from_css(of_css(of));
• page_counter_reset_watermark(&memcg->memory);
• return nbytes;

+}

static int memory_min_show(struct seq_file *m, void *v) { return seq_puts_memcg_tunable(m, @@ -6947,6 +6958,7 @@ static struct cftype memory_files[] = { .name = "peak", .flags = CFTYPE_NOT_ON_ROOT, .read_u64 = memory_peak_read,

• .write = memory_peak_write,
  

  }, { .name = "min",

@@ -7917,6 +7929,16 @@ static u64 swap_peak_read(struct cgroup_subsys_state *css, return (u64)memcg->swap.watermark * PAGE_SIZE; } +static ssize_t swap_peak_write(struct kernfs_open_file *of,

• 		 char *buf, size_t nbytes, loff_t off)
  

+{

• struct mem_cgroup *memcg = mem_cgroup_from_css(of_css(of));
• page_counter_reset_watermark(&memcg->swap);
• return nbytes;

+}

static int swap_high_show(struct seq_file *m, void *v) { return seq_puts_memcg_tunable(m, @@ -7999,6 +8021,7 @@ static struct cftype swap_files[] = { .name = "swap.peak", .flags = CFTYPE_NOT_ON_ROOT, .read_u64 = swap_peak_read,

• .write = swap_peak_write,
  

  }, { .name = "swap.events",

diff --git a/tools/testing/selftests/cgroup/test_memcontrol.c b/tools/testing/selftests/cgroup/test_memcontrol.c index c7c9572003a8..0326c317f1f2 100644 --- a/tools/testing/selftests/cgroup/test_memcontrol.c +++ b/tools/testing/selftests/cgroup/test_memcontrol.c @@ -161,12 +161,12 @@ static int alloc_pagecache_50M_check(const char *cgroup, void *arg) /*

• This test create a memory cgroup, allocates
• some anonymous memory and some pagecache

• • and check memory.current and some memory.stat values.

• • and checks memory.current, memory.peak, and some memory.stat values.
  */

-static int test_memcg_current(const char *root) +static int test_memcg_current_peak(const char *root) { int ret = KSFT_FAIL;

• long current;

• long current, peak, peak_reset; char *memcg;

memcg = cg_name(root, "memcg_test"); @@ -180,12 +180,32 @@ static int test_memcg_current(const char *root) if (current != 0) goto cleanup;

• peak = cg_read_long(memcg, "memory.peak");
• if (peak != 0)

• goto cleanup;
  

• if (cg_run(memcg, alloc_anon_50M_check, NULL)) goto cleanup;

• peak = cg_read_long(memcg, "memory.peak");
• if (peak < MB(50))

• goto cleanup;
  

• peak_reset = cg_write(memcg, "memory.peak", "\n");
• if (peak_reset != 0)

• goto cleanup;
  

• peak = cg_read_long(memcg, "memory.peak");
• if (peak > MB(30))

• goto cleanup;
  

• if (cg_run(memcg, alloc_pagecache_50M_check, NULL)) goto cleanup;

• peak = cg_read_long(memcg, "memory.peak");
• if (peak < MB(50))

• goto cleanup;
  

• ret = KSFT_PASS;

cleanup: @@ -815,13 +835,14 @@ static int alloc_anon_50M_check_swap(const char *cgroup, void *arg) /*

• This test checks that memory.swap.max limits the amount of

• • anonymous memory which can be swapped out.

• • anonymous memory which can be swapped out. Additionally, it verifies that
• • memory.swap.peak reflects the high watermark and can be reset.
  */

-static int test_memcg_swap_max(const char *root) +static int test_memcg_swap_max_peak(const char *root) { int ret = KSFT_FAIL; char *memcg;

• long max;

• long max, peak;

if (!is_swap_enabled()) return KSFT_SKIP; @@ -838,6 +859,12 @@ static int test_memcg_swap_max(const char *root) goto cleanup; }

• if (cg_read_long(memcg, "memory.swap.peak"))

• goto cleanup;
  

• if (cg_read_long(memcg, "memory.peak"))

• goto cleanup;
  

• if (cg_read_strcmp(memcg, "memory.max", "max\n")) goto cleanup;

@@ -860,6 +887,27 @@ static int test_memcg_swap_max(const char *root) if (cg_read_key_long(memcg, "memory.events", "oom_kill ") != 1) goto cleanup;

• peak = cg_read_long(memcg, "memory.peak");
• if (peak < MB(29))

• goto cleanup;
  

• peak = cg_read_long(memcg, "memory.swap.peak");
• if (peak < MB(29))

• goto cleanup;
  

• if (cg_write(memcg, "memory.swap.peak", "\n"))

• goto cleanup;
  

• if (cg_read_long(memcg, "memory.swap.peak") > MB(10))

• goto cleanup;
  

• if (cg_write(memcg, "memory.peak", "\n"))

• goto cleanup;
  

• if (cg_read_long(memcg, "memory.peak"))

• goto cleanup;
  

• if (cg_run(memcg, alloc_anon_50M_check_swap, (void *)MB(30))) goto cleanup;

@@ -867,6 +915,14 @@ static int test_memcg_swap_max(const char *root) if (max <= 0) goto cleanup;

• peak = cg_read_long(memcg, "memory.peak");
• if (peak < MB(29))

• goto cleanup;
  

• peak = cg_read_long(memcg, "memory.swap.peak");
• if (peak < MB(19))

• goto cleanup;
  

• ret = KSFT_PASS;

cleanup: @@ -1293,7 +1349,7 @@ struct memcg_test { const char *name; } tests[] = { T(test_memcg_subtree_control),

• T(test_memcg_current),

• T(test_memcg_current_peak), T(test_memcg_min), T(test_memcg_low), T(test_memcg_high),

@@ -1301,7 +1357,7 @@ struct memcg_test { T(test_memcg_max), T(test_memcg_reclaim), T(test_memcg_oom_events),

• T(test_memcg_swap_max),

• T(test_memcg_swap_max_peak), T(test_memcg_sock), T(test_memcg_oom_group_leaf_events), T(test_memcg_oom_group_parent_events),

-- 2.39.2