Bug 1616038 – rt-setup: include enable-netsocket-tstamp-static-key.c

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Bug 1616038 - rt-setup: include enable-netsocket-tstamp-static-key.c

Summary:	rt-setup: include enable-netsocket-tstamp-static-key.c

Status:	CLOSED ERRATA

Aliases:	None

Product:	Red Hat Enterprise Linux 7
Classification:	Red Hat
Component:	rt-setup (Show other bugs)
Sub Component:
Version:	7.6
Hardware:	Unspecified Unspecified

Priority	unspecified Severity unspecified
Target Milestone:	rc
Target Release:	---
Assigned To:	Clark Williams
QA Contact:	Jiri Kastner
Docs Contact:	Marie Dolezelova

URL:
Whiteboard:
Keywords:

Depends On:
Blocks:	1532680 1616043
	Show dependency tree / graph

Reported:	2018-08-14 15:10 EDT by Marcelo Tosatti
Modified:	2018-10-30 07:50 EDT (History)
CC List:	5 users (show)

See Also:
Fixed In Version:	rt-setup-2.0-1.el7
Doc Type:	Enhancement
Doc Text:	rt-entsk prevents IPI generation and delay of realtime tasks The chrony daemon, chronyd, enables or disables network timestamping, which activates a static key within the kernel. When a static key is enabled or disabled, three inter-processor interrupt (IPIs) are generated to notify other processors of the activation. Previously, rapid activation and deactivation of the chronyd static keys led to a delay of a realtime task. Consequently, a latency spike occurred. With this update, systemd starts the rt-entsk program, which keeps timestamping enabled and prevents the IPIs from being generated. As a result, IPI generation no longer occurs in a rapid succession, and realtime tasks are no longer delayed due to this bug.
Story Points:	---
Clone Of:
Clones:	1619407 (view as bug list)
Environment:
Last Closed:	2018-10-30 07:50:46 EDT
Type:	Bug
Regression:	---
Mount Type:	---
Documentation:	---
CRM:
Verified Versions:
Category:	---
oVirt Team:	---
RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---

Attachments	(Terms of Use)
daemon to enable timestamp on network sockets (969 bytes, text/x-csrc) 2018-08-14 15:12 EDT, Marcelo Tosatti	no flags	Details
Add an attachment (proposed patch, testcase, etc.)

External Trackers
Tracker	ID	Priority	Status	Summary	Last Updated
Red Hat Product Errata	RHBA-2018:3331	None	None	None	2018-10-30 07:50 EDT

Groups: None (edit)

Description Marcelo Tosatti 2018-08-14 15:10:30 EDT

Pei Zhang discovered and Daniel Bristot debugged a problem 
where chronyd enables/disables static keys for network timestamping.

The static key enable/disable process includes several IPIs and this causes
additional latency to -RT systems.

To workaround this particular problem, one can enable timestamping
on a socket separately from chronyd.

This is what the attached enable-netsocket-tstamp-static-key.c does.

Please include it in rt-setup so tuned profile can be patched
to start this daemon.

Comment 2 Marcelo Tosatti 2018-08-14 15:12 EDT

Created attachment 1475947 [details]
daemon to enable timestamp on network sockets

Comment 14 errata-xmlrpc 2018-10-30 07:50:46 EDT

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://access.redhat.com/errata/RHBA-2018:3331

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