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selftests: memcg: adjust expected reclaim values of protected cgroups

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The numbers are not easy to derive in a closed form (certainly mere
protections ratios do not apply), therefore use a simulation to obtain
expected numbers.

Link: https://lkml.kernel.org/r/20220518161859.21565-4-mkoutny@suse.com
Signed-off-by: Michal Koutný <mkoutny@suse.com>
Acked-by: Roman Gushchin <roman.gushchin@linux.dev>
Cc: David Vernet <void@manifault.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Richard Palethorpe <rpalethorpe@suse.de>
Cc: Shakeel Butt <shakeelb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Michal Koutný 2022-05-18 18:18:57 +02:00 committed by akpm
parent 1d09069f53
commit f10b6e9a8e
3 changed files with 107 additions and 12 deletions
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1
MAINTAINERS
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@ -5029,6 +5029,7 @@ L: linux-mm@kvack.org
S: Maintained
F: mm/memcontrol.c
F: mm/swap_cgroup.c
F: tools/testing/selftests/cgroup/memcg_protection.m
F: tools/testing/selftests/cgroup/test_kmem.c
F: tools/testing/selftests/cgroup/test_memcontrol.c

89
tools/testing/selftests/cgroup/memcg_protection.m Normal file
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@ -0,0 +1,89 @@
% SPDX-License-Identifier: GPL-2.0
%
% run as: octave-cli memcg_protection.m
%
% This script simulates reclaim protection behavior on a single level of memcg
% hierarchy to illustrate how overcommitted protection spreads among siblings
% (as it depends also on their current consumption).
%
% Simulation assumes siblings consumed the initial amount of memory (w/out
% reclaim) and then the reclaim starts, all memory is reclaimable, i.e. treated
% same. It simulates only non-low reclaim and assumes all memory.min = 0.
%
% Input configurations
% --------------------
% E number parent effective protection
% n vector nominal protection of siblings set at the given level (memory.low)
% c vector current consumption -,,- (memory.current)
% example from testcase (values in GB)
E = 50 / 1024;
n = [75 25 0 500 ] / 1024;
c = [50 50 50 0] / 1024;
% Reclaim parameters
% ------------------
% Minimal reclaim amount (GB)
cluster = 32*4 / 2**20;
% Reclaim coefficient (think as 0.5^sc->priority)
alpha = .1
% Simulation parameters
% ---------------------
epsilon = 1e-7;
timeout = 1000;
% Simulation loop
% ---------------
ch = [];
eh = [];
rh = [];
for t = 1:timeout
% low_usage
u = min(c, n);
siblings = sum(u);
% effective_protection()
protected = min(n, c); % start with nominal
e = protected * min(1, E / siblings); % normalize overcommit
% recursive protection
unclaimed = max(0, E - siblings);
parent_overuse = sum(c) - siblings;
if (unclaimed > 0 && parent_overuse > 0)
overuse = max(0, c - protected);
e += unclaimed * (overuse / parent_overuse);
endif
% get_scan_count()
r = alpha * c; % assume all memory is in a single LRU list
% commit 1bc63fb1272b ("mm, memcg: make scan aggression always exclude protection")
sz = max(e, c);
r .*= (1 - (e+epsilon) ./ (sz+epsilon));
% uncomment to debug prints
% e, c, r
% nothing to reclaim, reached equilibrium
if max(r) < epsilon
break;
endif
% SWAP_CLUSTER_MAX roundup
r = max(r, (r > epsilon) .* cluster);
% XXX here I do parallel reclaim of all siblings
% in reality reclaim is serialized and each sibling recalculates own residual
c = max(c - r, 0);
ch = [ch ; c];
eh = [eh ; e];
rh = [rh ; r];
endfor
t
c, e

29
tools/testing/selftests/cgroup/test_memcontrol.c
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@ -248,7 +248,7 @@ static int cg_test_proc_killed(const char *cgroup)
/*
* First, this test creates the following hierarchy:
* A memory.min = 50M, memory.max = 200M
* A/B memory.min = 50M, memory.current = 50M
* A/B memory.min = 50M
* A/B/C memory.min = 75M, memory.current = 50M
* A/B/D memory.min = 25M, memory.current = 50M
* A/B/E memory.min = 0, memory.current = 50M
@ -259,10 +259,13 @@ static int cg_test_proc_killed(const char *cgroup)
* Then it creates A/G and creates a significant
* memory pressure in it.
*
* Then it checks actual memory usages and expects that:
* A/B memory.current ~= 50M
* A/B/C memory.current ~= 33M
* A/B/D memory.current ~= 17M
* A/B/F memory.current ~= 0
* A/B/C memory.current ~= 29M
* A/B/D memory.current ~= 21M
* A/B/E memory.current ~= 0
* A/B/F memory.current = 0
* (for origin of the numbers, see model in memcg_protection.m.)
*
* After that it tries to allocate more than there is
* unprotected memory in A available, and checks
@ -365,10 +368,10 @@ static int test_memcg_min(const char *root)
for (i = 0; i < ARRAY_SIZE(children); i++)
c[i] = cg_read_long(children[i], "memory.current");
if (!values_close(c[0], MB(33), 10))
if (!values_close(c[0], MB(29), 10))
goto cleanup;
if (!values_close(c[1], MB(17), 10))
if (!values_close(c[1], MB(21), 10))
goto cleanup;
if (c[3] != 0)
@ -405,7 +408,7 @@ cleanup:
/*
* First, this test creates the following hierarchy:
* A memory.low = 50M, memory.max = 200M
* A/B memory.low = 50M, memory.current = 50M
* A/B memory.low = 50M
* A/B/C memory.low = 75M, memory.current = 50M
* A/B/D memory.low = 25M, memory.current = 50M
* A/B/E memory.low = 0, memory.current = 50M
@ -417,9 +420,11 @@ cleanup:
*
* Then it checks actual memory usages and expects that:
* A/B memory.current ~= 50M
* A/B/ memory.current ~= 33M
* A/B/D memory.current ~= 17M
* A/B/F memory.current ~= 0
* A/B/C memory.current ~= 29M
* A/B/D memory.current ~= 21M
* A/B/E memory.current ~= 0
* A/B/F memory.current = 0
* (for origin of the numbers, see model in memcg_protection.m.)
*
* After that it tries to allocate more than there is
* unprotected memory in A available,
@ -512,10 +517,10 @@ static int test_memcg_low(const char *root)
for (i = 0; i < ARRAY_SIZE(children); i++)
c[i] = cg_read_long(children[i], "memory.current");
if (!values_close(c[0], MB(33), 10))
if (!values_close(c[0], MB(29), 10))
goto cleanup;
if (!values_close(c[1], MB(17), 10))
if (!values_close(c[1], MB(21), 10))
goto cleanup;
if (c[3] != 0)