"NETEM - fq_codel and pfifo_fast change/add tc rule"

Post #303039021 by Neo on Thursday 19th of September 2019 11:05:17 PM

As as recall, the netem package has issues related to granularity; and when I did a quick look, I found this in the man page:

The main known limitation of Netem are related to timer granularity, since Linux is not a real-time operating system.
This could be way off base, but perhaps using a 0.5% loss parameter is too granular for Linux?

Did you experiment using a larger parameter, such as 5% or even 2% first, to test?

Sorry if this is not helpful or I'm way off the mark.

EDIT: Yes, I am way off the mark... I just read this in the docs on Packet Loss:

Ref: https://wiki.linuxfoundation.org/net...em#packet_loss

Packet loss
Random packet loss is specified in the 'tc' command in percent. The smallest possible non-zero value is:

232 = 0.0000000232%

 # tc qdisc change dev eth0 root netem loss 0.1%
This causes 1/10th of a percent (i.e 1 out of 1000) packets to be randomly dropped.

An optional correlation may also be added. This causes the random number generator to be less random and can be used to emulate packet burst losses.

 # tc qdisc change dev eth0 root netem loss 0.3% 25%
This will cause 0.3% of packets to be lost, and each successive probability depends by a quarter on the last one.

Probn = .25 * Probn-1 + .75 * Random

I'm really interested in this topic, so looking forward to any updates. What version of Linux are you using? I may install netem on Ubuntu and check it out.

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AUDIT_ADD_RULE_DATA(3)						  Linux Audit API					    AUDIT_ADD_RULE_DATA(3)

audit_add_rule_data - Add new audit rule SYNOPSIS
#include <libaudit.h> int audit_add_rule_data (int fd, struct audit_rule_data *rule, int flags, int action); DESCRIPTION
audit_add_rule adds an audit rule previously constructed with audit_rule_fieldpair_data(3) to one of several kernel event filters. The fil- ter is specified by the flags argument. Possible values for flags are: o AUDIT_FILTER_USER - Apply rule to userspace generated messages. o AUDIT_FILTER_TASK - Apply rule at task creation (not syscall). o AUDIT_FILTER_EXIT - Apply rule at syscall exit. o AUDIT_FILTER_TYPE - Apply rule at audit_log_start. The rule's action has two possible values: o AUDIT_NEVER - Do not build context if rule matches. o AUDIT_ALWAYS - Generate audit record if rule matches. RETURN VALUE
The return value is <= 0 on error, otherwise it is the netlink sequence id number. This function can have any error that sendto would encounter. SEE ALSO
audit_rule_fieldpair_data(3), audit_delete_rule_data(3), auditctl(8). AUTHOR
Steve Grubb. Red Hat Aug 2009 AUDIT_ADD_RULE_DATA(3)

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