Bug 1253452 - Errors on "Reducing the TCP Delayed Ack Timeout" doc
Errors on "Reducing the TCP Delayed Ack Timeout" doc
Product: Red Hat Enterprise MRG
Classification: Red Hat
Component: Realtime_Tuning_Guide (Show other bugs)
x86_64 Linux
unspecified Severity medium
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Assigned To: Scott Mumford
MRG Quality Engineering
Depends On:
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Reported: 2015-08-13 13:27 EDT by Daniel Bristot de Oliveira
Modified: 2015-11-11 20:07 EST (History)
5 users (show)

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Doc Type: Bug Fix
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Last Closed: 2015-11-11 20:07:48 EST
Type: Bug
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Description Daniel Bristot de Oliveira 2015-08-13 13:27:01 EDT
Description of problem:

There are two errors at the following chapter/section [1]:
  2. General System Tuning
     2.13. Reducing the TCP delayed ack timeout

at the following statements:

1) "This value defaults to 40ms."
   This is the default value on non-rt kernel. On rt kernel it is 4ms.

2) "Write the desired minimum value, in microseconds, to /proc/sys/net/ipv4/tcp_delack_min:"
   The correct unit of time is milliseconds, and not microseconds.

Moreover, the patch that implements this feature [2] also includes the tcp_ato_min knob, but I did not find the documentation for it.

[1] https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_MRG/2/html/Realtime_Tuning_Guide/sect-Realtime_Tuning_Guide-General_System_Tuning-Reducing_the_TCP_delayed_ack_timeout.html

[2] kernel-rt specific commit:
c00451d MRG: RFC: Nagle latency tuning

[ this bug is the same report of BZ1253448 ]

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