Public bug reported:
Ubuntu 24.04 kernels 6.14 and 6.17 set ENA_INTR_INITIAL_TX_INTERVAL_USECS to 0
in
drivers/net/ethernet/amazon/ena/ena_com.h, disabling TX interrupt coalescing.
This
causes 10-25% Nginx performance regression compared to Ubuntu 22.04, which
correctly
uses tx-usecs=64 matching the upstream default.This is likely to impact any
network
throughput-heavy application running on EC2.
TEST RESULTS (Nginx, RPS, Ubuntu 24.04 kernel 6.17.0-1007-aws)
m8g.2xlarge (Graviton4):
Ubuntu 22.04 baseline: 429,911 RPS (baseline)
Ubuntu 24.04: 384,424 RPS (-10.6%)
Ubuntu 24.04 + tx-usecs=64: 417,520 RPS (-2.9%)
m8i.2xlarge (Intel Sapphire Rapids):
Ubuntu 22.04 baseline: 305,446 RPS (baseline)
Ubuntu 24.04: 230,354 RPS (-24.6%)
Ubuntu 24.04 + tx-usecs=64: 302,420 RPS (-1.0%)
Please restore ENA_INTR_INITIAL_TX_INTERVAL_USECS to 64 to match upstream, and
ensure this fix persists across future kernel rebases including Ubuntu 26.04.
** Affects: linux-aws (Ubuntu)
Importance: Undecided
Status: New
** Tags: aws kernel-bug performance regression-release
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https://bugs.launchpad.net/bugs/2144038
Title:
ENA driver tx-usecs=0 causes 10-30% nginx performance regression on
Ubuntu 24.04
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