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VM problem (2.4.0-test11)

DISCUSSION Jussi Laako 4 participants 5 messages Dec 12, 2000 – Dec 14, 2000

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#0 lore raw

Hello,

Would it be possible to implement some VM CPUtime/bandwidth limitation?

We have server used by multiple developers. Problem is when someone happens to implement memory hole to application the system goes wild swapping and ALL other activity stops. No response to keyboard/mouse events nor any network traffic. Only disk system running wildly. No way to stop the memoryhog application, only way out of this situation is to hit reset-button and hope that no important data is lost. Same thing happens when I forget to end some large matrix operation with semicolon in Octave... (and 2.2.x kernels at least with Octave) I'm still considering this as local DOS attack because normal user is able to overload the system.

Rebooting system all the time is annoying.

It would be nice to be able to tell system that "this process may use max 256 MB of memory and 10% of disk IO bandwidth and 25% of network bandwidth and network IO latency is critical and disk io is not".

Kernel is stock except Andrew Morton's lowlatency patch.

Regards,

- Jussi Laako

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#1 lore raw
Quoted 5 lines · Jussi Laako

Hello,

Would it be possible to implement some VM CPUtime/bandwidth limitation?

<snip>

Just to not miss the obvious: You know about ulimit(3)?

man 3 ulimit
help ulimit (when in bash).

Marc

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#2 lore raw
In reply to Jussi Laako
Quoted 2 lines · Marc Mutz

Just to not miss the obvious: You know about ulimit(3)?

Yes, but it doesn't stop deadlocks caused by kernel's VM system going wild... I think that no matter what user process does, root should be always able to stop it. User process should never be able to render whole system unusable.

Hard memory limit per process doesn't stop this from happening, because it depends overall system memory usage and allocation rate. It's completely different if memory usage goes from 200 MB to 512 MB in 1 usec or 1 week.

- Jussi Laako

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#3 lore raw
In reply to Jussi Laako
Quoted 9 lines · On Wed, 13 Dec 2000 00:25:25 Jussi Laako wrote:
Quoted 2 lines · Marc Mutz

Just to not miss the obvious: You know about ulimit(3)?

Yes, but it doesn't stop deadlocks caused by kernel's VM system going wild... I think that no matter what user process does, root should be always able to stop it. User process should never be able to render whole system unusable.

That is just some issue that was discussed in this list recently. Look in the list
for 'oom killer' subjects.
There are various patches-ways-to-do available, kernel gurus are still working on it...
(leave always some 4% of mem for root, kill some process when mem is exhausted, which one to kill...)

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#4 lore raw
In reply to Jussi Laako
Quoted 4 lines · J . A . Magallon

There are various patches-ways-to-do available, kernel gurus are still working on it...
(leave always some 4% of mem for root, kill some process when mem is exhausted, which one to kill...)

which is a bad idea; 4% of 1GB is a waste, and 4% of 8mb is really pushing it (that is, if we are speaking about root just doing cleanup stuff)

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