memory_compare script doesn't account for all RAM usage

Bug #1019240 reported by Brendan Donegan on 2012-06-29
This bug affects 3 people
Affects Status Importance Assigned to Milestone
Provider for Plainbox - Checkbox

Bug Description

Currently the memory_compare script checks dmidecode to see how much RAM is installed on the system and then simply checks the MemTotal field of /proc/meminfo to see if it's accounted for. It appears to be the case on many systems that some RAM is unaccounted for. This is unlikely to be an OS bug so the script should account for other RAM usage, for example by discrete GPUs using it as video memory and make sure it is all used legitimately.

As pointed out in another bug, the Unified Memory Architecture graphics cards can be one reason why we see memory go 'missing'

Changed in checkbox:
status: New → Confirmed
importance: Undecided → High

This false positive is occuring on very few systems now in the SRU testing so I'm lowering the importance to Medium

Changed in checkbox:
importance: High → Medium

In reviewing another merge request I've discovered that a way to view the graphics memory used by a card is in 'lspci -v'. Exploring this as a potential way to account for the 'lost' memory.

Changed in checkbox:
status: Confirmed → In Progress
assignee: nobody → Brendan Donegan (brendan-donegan)
Changed in checkbox:
assignee: Brendan Donegan (brendan-donegan) → nobody
status: In Progress → Confirmed
Daniel Manrique (roadmr) on 2013-06-05
tags: added: scripts
tags: added: saucy
tags: added: ce-qa-concern
Zygmunt Krynicki (zyga) on 2014-04-23
affects: checkbox → plainbox-provider-checkbox
Pierre Equoy (pieq) wrote :

@Brendan, this bug was opened almost 3 years ago. Is it still relevant? Do we have data regarding the number of units where this test fails because of this?

The data on failures would be in the certification site and would need to be analysed to figure out if and why this is still happening. I know it was still an issue when I left the team so unless improvements have been made to the script since then it is probably still happening

Sylvain Pineau (sylvain-pineau) wrote :

To work around this issue we defined threshold percentages.
They were made to account for small memory systems that share
system RAM with an onboard GPU. So for something less than 2GB, we
allow for up to 25% difference to account for shared Video RAM up to
512MB. The 20% threshold for 6 GB allows for up to 1.2GB shared RAM.

Changed in plainbox-provider-checkbox:
status: Confirmed → Won't Fix
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