| From: |
| Artem Savkov <asavkov-AT-redhat.com> |
| To: |
| Thomas Gleixner <tglx-AT-linutronix.de>, Josh Poimboeuf <jpoimboe-AT-redhat.com>, Anna-Maria Behnsen <anna-maria-AT-linutronix.de>, netdev-AT-vger.kernel.org |
| Subject: |
| [PATCH v4 0/2] Upper bound kernel timers |
| Date: |
| Thu, 07 Apr 2022 09:52:40 +0200 |
| Message-ID: |
| <20220407075242.118253-1-asavkov@redhat.com> |
| Cc: |
| davem-AT-davemloft.net, yoshfuji-AT-linux-ipv6.org, dsahern-AT-kernel.org, linux-kernel-AT-vger.kernel.org, Artem Savkov <asavkov-AT-redhat.com> |
| Archive-link: |
| Article |
As previously discussed [1] we had a report of a regression in TCP keepalive
timer where timers were up to 4 minutes late resulting in disconnects.
This patchset tries to fix the problem by introducing upper bound kernel timers
and making tcp keepalive timer use those.
[1] https://lore.kernel.org/all/20210302001054.4qgrvnkltvkgik...
---
Changes in v4:
- Drop any attempts to be smart when calculating timer adjustment and always
substract LVL_GRAN so that base clock lag won't be such a problem. This
means that in some cases we will always be early, but all we want is not to
be late.
Changes in v3:
- A different approach: instead of introducing upper bound timers try to
account for timer wheen granularity on timer (re)arming step.
- Not sure whether moving lvl calculation into a separate function is worth
it.
- Had a hard time naming the upper_bount_timeout() function - any suggestions
welcome.
Changes in v2:
- TIMER_UPPER_BOUND flag description added as a comment in timer.h
- Code style fixes
- More elaborate commit message in timer commit
Artem Savkov (2):
timer: add a function to adjust timeouts to be upper bound
net: make tcp keepalive timer upper bound
include/linux/timer.h | 1 +
kernel/time/timer.c | 68 ++++++++++++++++++++++++++-------
net/ipv4/inet_connection_sock.c | 2 +-
3 files changed, 57 insertions(+), 14 deletions(-)
--
2.34.1
