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tcp_buffer_tuner: reduce tcp_[rw]mem max when correlated with latency… #134

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Merged
alan-maguire merged 1 commit into from
Dec 18, 2024
Merged

tcp_buffer_tuner: reduce tcp_[rw]mem max when correlated with latency… #134

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15 changes: 9 additions & 6 deletions src/tcp_buffer_tuner.c
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Original file line number Diff line number Diff line change
Expand Up @@ -30,9 +30,9 @@ static struct bpftunable_scenario scenarios[] = {
"Need to increase buffer size(s) to maximize throughput" },
{ TCP_BUFFER_DECREASE, "need to decrease TCP buffer size(s)",
"Need to decrease buffer size(s) to reduce memory utilization" },
{ TCP_BUFFER_NOCHANGE_LATENCY,
"need to retain TCP buffer size due to latency",
"Latency is starting to correlate with buffer size increases, so do not make buffer size increase to avoid this effect" },
{ TCP_BUFFER_DECREASE_LATENCY,
"need to decrease TCP buffer size due to latency",
"Latency is starting to correlate with buffer size increases, so decrease buffer size to avoid this effect" },
{ TCP_MEM_PRESSURE, "approaching TCP memory pressure",
"Since memory pressure/exhaustion are unstable system states, adjust tcp memory-related tunables" },
{ TCP_MEM_EXHAUSTION, "approaching TCP memory exhaustion",
Expand Down Expand Up @@ -228,7 +228,7 @@ void event_handler(struct bpftuner *tuner,
tunable, key.netns_cookie, new[0], new[1], new[2],
covar_compute(&c), corr);
if (corr > CORR_THRESHOLD && scenario == TCP_BUFFER_INCREASE)
scenario = TCP_BUFFER_NOCHANGE_LATENCY;
scenario = TCP_BUFFER_DECREASE_LATENCY;
}
switch (id) {
case TCP_BUFFER_TCP_MEM:
Expand All @@ -248,9 +248,12 @@ void event_handler(struct bpftuner *tuner,
case TCP_BUFFER_DECREASE:
reason = lowmem;
break;
case TCP_BUFFER_NOCHANGE_LATENCY:
case TCP_BUFFER_DECREASE_LATENCY:
reason = "correlation between buffer size increase and latency";
new[2] = old[2];
new[2] = BPFTUNE_SHRINK_BY_DELTA(old[2]);
/* ensure we do not shrink too far */
if (new[2] <= new[1])
return;
break;
}
bpftuner_tunable_sysctl_write(tuner, id, scenario,
Expand Down
2 changes: 1 addition & 1 deletion src/tcp_buffer_tuner.h
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Original file line number Diff line number Diff line change
Expand Up @@ -34,7 +34,7 @@ enum tcp_buffer_tunables {
enum tcp_buffer_scenarios {
TCP_BUFFER_INCREASE,
TCP_BUFFER_DECREASE,
TCP_BUFFER_NOCHANGE_LATENCY,
TCP_BUFFER_DECREASE_LATENCY,
TCP_MEM_PRESSURE,
TCP_MEM_EXHAUSTION,
TCP_MAX_ORPHANS_INCREASE,
Expand Down