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AndrewAmmerlaan
Developer
Joined: 25 Jun 2014
Posts: 262
Location: Nijmegen
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 Posted: Fri Feb 09, 2018 9:07 pm Post subject: Ram memory usage, strangly high |
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Hi all,
I'm curious as to why I keep running out of ram, even though it should be enough. So here's the thing when I check top I see this:
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PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
6457 andrew 20 0 17.003g 6.342g 20.3m S 58.1 40.7 340:18.08 java
16610 andrew 20 0 4689.1m 142.0m 30.0m S 14.0 0.9 46:55.88 clementine
16489 andrew 20 0 3403.3m 50.4m 21.6m S 8.3 0.3 27:02.87 kwin_x11
16302 root 20 0 525.7m 44.8m 30.3m S 8.0 0.3 24:21.35 X
17110 andrew 20 0 2622.8m 489.6m 72.3m S 7.6 3.1 2:34.77 Web Content
16718 andrew 20 0 2687.0m 221.0m 45.7m S 5.6 1.4 20:54.59 thunderbird
16507 andrew 20 0 5350.4m 215.5m 43.3m S 5.3 1.4 16:49.20 plasmashell
16962 andrew 20 0 2852.8m 624.7m 77.6m S 4.3 3.9 5:37.33 Web Content
16703 andrew 20 0 9816.5m 772.7m 77.1m S 3.0 4.8 11:24.02 firefox
16583 andrew 9 -11 4609.1m 26.9m 22.5m S 2.7 0.2 9:39.67 pulseaudio
16594 andrew 20 0 933.2m 72.1m 48.0m S 1.0 0.5 0:15.71 yakuake
32633 andrew 20 0 1554.5m 75.4m 40.8m S 1.0 0.5 0:49.03 Discord
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As you can see the java process is using about 6.5GB, without java running my system runs at about 2 to 3 GB. Lets make that 4 just to be safe. Thus the memory used by running processes is about 10.5GB. So far so good, that should fit in the 16 I have available. Now this is what free shows me:
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andrew@Andrew-Gentoo ~ $ free -h
total used free shared buff/cache available
Mem: 15G 14G 322M 384M 990M 1.3G
Swap: 7.1G 1.1G 6.0G
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So there's an buff/cache and shared part that adds an extra 1.5GB, Lets add that to the 10.5GB, which makes 12GB as an estimate that is significantly rounded up. Now I have been reading up on how linux manages ram, and how it will fill empty ram with buff/cache, but the cache is to small to explain all extra memory usage. What is using the remaining unaccounted for 2+GB?
Why is this a problem? Well it's not a very big one, but I curious as to what's going on here. And waiting for an application to get pulled out of swap gets annoying after a while. I can of course reduce -xmx in java, but I'd rather have more information on what is going on here before I do.
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OS: Gentoo 6.7.3-gentoo-dist, ~amd64, 17.1/desktop/plasma/systemd/merged-usr
MB: MSI Z370-A PRO
CPU: Intel Core i9-9900KS
GPU: Intel Arc A770 16GB & Intel UHD Graphics 630
SSD: Samsung 970 EVO Plus 2 TB
RAM: Crucial Ballistix 32GB DDR4-2400 |
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eccerr0r
Watchman
Joined: 01 Jul 2004
Posts: 9677
Location: almost Mile High in the USA
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| Posted: Sat Feb 10, 2018 9:07 pm Post subject: |
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These rough estimates are making things round the wrong way. So, not enough accurate data here to tell. You can see your firefox is using a tremendous amount of memory that changes, so you need to take that into account. It''s got 1.9GB allocated in physical memory by itself.
Also you're starting with 15G (what's your free without -h say?) due to the kernel using RAM for page tables, video memory if you don't have dedicated video memory, and unusable due to hardware issues.
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Intel Core i7 2700K/Radeon R7 250/24GB DDR3/256GB SSD
What am I supposed watching? |
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AndrewAmmerlaan
Developer
Joined: 25 Jun 2014
Posts: 262
Location: Nijmegen
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| Posted: Sun Feb 11, 2018 8:34 am Post subject: |
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I rounded everything up intentionally, so that the end result would be rounded up as well. Firefox does indeed use a lot of ram, but this is what free shows without java running:
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andrew@Andrew-Gentoo ~ $ free
total used free shared buff/cache available
Mem: 16345300 3246124 10865148 33872 2234028 14080736
Swap: 7488508 0 7488508
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It will fluctuate between 2 and 3, mostly due to firefox, and in my original post I used 4GB as an estimate, so I would say that that is rounded the right way. Wouldn't it make sense for the ram usage with java running to be just this 'at rest' value + the memory that java uses + additional cache? Because that is not what seems to happen.
Regarding video memory: I have 2GB of vram, and 1GB of GTT memory. But if I understand correctly what you're saying, the vram will overflow into ram if it's full? That would certainly explain part of the additional ram usage.
_________________
OS: Gentoo 6.7.3-gentoo-dist, ~amd64, 17.1/desktop/plasma/systemd/merged-usr
MB: MSI Z370-A PRO
CPU: Intel Core i9-9900KS
GPU: Intel Arc A770 16GB & Intel UHD Graphics 630
SSD: Samsung 970 EVO Plus 2 TB
RAM: Crucial Ballistix 32GB DDR4-2400 |
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