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[David Favor <david@xxxxxxxxxxxxxx>]

Public bug reported:

Tracking this down took forever + I believe I now have a test case.

Top priority, is finding a temporary fix for this problem.

Here's the symptom...

lxd: net12-david-favor # ab -vvv -k -t 10 -n 100000 -c 5 https://DavidFavor.com/foo.txt 2>&1 | egrep -e ^Requests -e ^Failed -e ^Time -e "^Document Length:"
Document Length:        8192 bytes
Time taken for tests:   8.540 seconds
Failed requests:        0
Requests per second:    11710.24 [#/sec] (mean)
Time per request:       0.427 [ms] (mean)
Time per request:       0.085 [ms] (mean, across all concurrent requests)

ab -vvv -k -t 10 -n 100000 -c 5 https://DavidFavor.com/foo.txt 2>&1 | egrep -e ^Requests -e ^Failed -e ^Time -e "^Document Length:"
Document Length:        8193 bytes
Time taken for tests:   10.087 seconds
Failed requests:        5
Requests per second:    1.19 [#/sec] (mean)
Time per request:       4202.710 [ms] (mean)
Time per request:       840.542 [ms] (mean, across all concurrent requests)

First run 1-8192 byte files work great. They serve fast with 0 failed
requests.

Second run of 8193-... byte files slow to a crawl + produce request
failures + notice the "Time taken for tests", which seems to relate to
socket housekeeping tests, becomes very slow.

This seems to be an actual apache problem, rather than an ab problem, as
all sites I host seem to slow down, when Apache2-4.27 is installed.

I'll setup a testbed system running Zesty, for which I can provide a login, for debugging, if required.
_______

lxd: net12-david-favor # uname -a
Linux net12-david-favor 4.8.0-30-generic #32-Ubuntu SMP Fri Dec 2 03:43:27 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux

lxd: net12-david-favor # lsb_release -a
No LSB modules are available.
Distributor ID:	Ubuntu
Description:	Ubuntu 16.10
Release:	16.10
Codename:	yakkety

lxd: net12-david-favor # apt-cache policy apache2
apache2:
  Installed: 2.4.27-0.1+ubuntu16.10.1+deb.sury.org+1
  Candidate: 2.4.27-0.1+ubuntu16.10.1+deb.sury.org+1
  Version table:
 *** 2.4.27-0.1+ubuntu16.10.1+deb.sury.org+1 500
        500 http://ppa.launchpad.net/ondrej/apache2/ubuntu yakkety/main amd64 Packages
        100 /var/lib/dpkg/status
     2.4.18-2ubuntu4.2 500
        500 http://archive.ubuntu.com/ubuntu yakkety-updates/main amd64 Packages
        500 http://security.ubuntu.com/ubuntu yakkety-security/main amd64 Packages
     2.4.18-2ubuntu4 500
        500 http://archive.ubuntu.com/ubuntu yakkety/main amd64 Packages

** Affects: apache2 (Ubuntu)
     Importance: Undecided
         Status: New

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https://bugs.launchpad.net/bugs/1704168

Title:
  Apache-2.4.27 massive slow down for files >8192 bytes long

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