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