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Bug 1106656 - Docker run --memory value doesn't match cgroup value
Summary: Docker run --memory value doesn't match cgroup value
Keywords:
Status: CLOSED ERRATA
Alias: None
Product: Red Hat Enterprise Linux 7
Classification: Red Hat
Component: docker
Version: 7.0
Hardware: x86_64
OS: Linux
unspecified
low
Target Milestone: rc
: ---
Assignee: Matthew Heon
QA Contact: Virtualization Bugs
URL:
Whiteboard:
Depends On:
Blocks: 1109938
TreeView+ depends on / blocked
 
Reported: 2014-06-09 17:00 UTC by Chris Evich
Modified: 2019-03-06 01:50 UTC (History)
6 users (show)

Fixed In Version:
Doc Type: Bug Fix
Doc Text:
Clone Of:
Environment:
Last Closed: 2014-09-18 20:45:44 UTC
Target Upstream Version:
Embargoed:

Attachments (Terms of Use)


Links
System ID Private Priority Status Summary Last Updated
Red Hat Product Errata RHBA-2014:1266 0 normal SHIPPED_LIVE docker bug fix and enhancement update 2014-09-19 00:45:12 UTC

Description Chris Evich 2014-06-09 17:00:46 UTC 
Description of problem:
Some values to the --memory option result in an exact match to the cgroup value, others are slightly off.  If expected, then this could be fixed with a documentation update.

Version-Release number of selected component (if applicable):
docker-0.11.1-10.el7.x86_64

How reproducible:
very

Steps to Reproduce:

docker run -d -t -m 524889 some_image bash
...
cat /sys/fs/cgroup/memory/system.slice/.../memory.limit_in_bytes 
5246976

Same result for --memory 524889 value suffixes of:
b and B  => cgroup: 5246976
k and K  => cgroup: 5368721408

Suffixes for 'm' and 'g' seem to correctly represent specified value.

Actual results:
Values specified on command line sometimes don't match value in cgroup file

Expected results:
Values from command line should match value in cgroup file, a message should
be printed or logged if the value is altered, and/or value manipulation/conformity rules should be documented for the --memory option.
Comment 1 Guohua Ouyang 2014-06-10 01:56:53 UTC 
I think I caught this, the memory size must be a multiper of 4096.

I tested below:
set memory limits    crgoup memory limits
=================    ========================
1024m                1073741824
1g                   1073741824
1048576k             1073741824
1073741824           1073741824
1048576              1048576
1024575              1048576
1048577              1052672 (1048576 + 4096)
1052673              1056768 (1052672 + 4096)
=================    ========================

so this should be not a bug.
Comment 2 Guohua Ouyang 2014-06-10 02:13:41 UTC 
for the example in the bug, 524889 is between 524288 ~ 528384, so the value in cgroups should be the later.

#docker run -d -t -m 524889 some_image bash

# cat docker-dd95e808b318c29f3f79266118768d4cd196f3a9f2eea88bc8d473a71b58b27d.scope/memory.limit_in_bytes 
528384

>>>528384 - 524288 (1024*4*(524889 / 4096)
4096
Comment 3 Chris Evich 2014-06-10 14:59:48 UTC 
Great, thanks for confirming.  Moving this to 'low' severity then since it'll just be a short documentation/man page update then.  I'd suggest something like:

The value may be rounded up to the next multiple of the host's memory page size(?) (typically 4k) unless an exact multiple is given.
Comment 4 Matthew Heon 2014-06-25 16:47:59 UTC 
Patch sent to upstream for this (https://github.com/dotcloud/docker/pull/6680). Should appear in our builds of docker-1.0 for RHEL7 soon.
Comment 5 Daniel Walsh 2014-06-27 16:26:44 UTC 
Fixed in docker-1.0
Comment 10 errata-xmlrpc 2014-09-18 20:45:44 UTC 
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.

http://rhn.redhat.com/errata/RHBA-2014-1266.html
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