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1% SPDX-License-Identifier: GPL-2.02%3% run as: octave-cli memcg_protection.m4%5% This script simulates reclaim protection behavior on a single level of memcg6% hierarchy to illustrate how overcommitted protection spreads among siblings7% (as it depends also on their current consumption).8%9% Simulation assumes siblings consumed the initial amount of memory (w/out10% reclaim) and then the reclaim starts, all memory is reclaimable, i.e. treated11% same. It simulates only non-low reclaim and assumes all memory.min = 0.12%13% Input configurations14% --------------------15% E number parent effective protection16% n vector nominal protection of siblings set at the given level (memory.low)17% c vector current consumption -,,- (memory.current)18 19% example from testcase (values in GB)20E = 50 / 1024;21n = [75 25 0 500 ] / 1024;22c = [50 50 50 0] / 1024;23 24% Reclaim parameters25% ------------------26 27% Minimal reclaim amount (GB)28cluster = 32*4 / 2**20;29 30% Reclaim coefficient (think as 0.5^sc->priority)31alpha = .132 33% Simulation parameters34% ---------------------35epsilon = 1e-7;36timeout = 1000;37 38% Simulation loop39% ---------------40 41ch = [];42eh = [];43rh = [];44 45for t = 1:timeout46 % low_usage47 u = min(c, n);48 siblings = sum(u);49 50 % effective_protection()51 protected = min(n, c); % start with nominal52 e = protected * min(1, E / siblings); % normalize overcommit53 54 % recursive protection55 unclaimed = max(0, E - siblings);56 parent_overuse = sum(c) - siblings;57 if (unclaimed > 0 && parent_overuse > 0)58 overuse = max(0, c - protected);59 e += unclaimed * (overuse / parent_overuse);60 endif61 62 % get_scan_count()63 r = alpha * c; % assume all memory is in a single LRU list64 65 % commit 1bc63fb1272b ("mm, memcg: make scan aggression always exclude protection")66 sz = max(e, c);67 r .*= (1 - (e+epsilon) ./ (sz+epsilon));68 69 % uncomment to debug prints70 % e, c, r71 72 % nothing to reclaim, reached equilibrium73 if max(r) < epsilon74 break;75 endif76 77 % SWAP_CLUSTER_MAX roundup78 r = max(r, (r > epsilon) .* cluster);79 % XXX here I do parallel reclaim of all siblings80 % in reality reclaim is serialized and each sibling recalculates own residual81 c = max(c - r, 0);82 83 ch = [ch ; c];84 eh = [eh ; e];85 rh = [rh ; r];86endfor87 88t89c, e90