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How to free Vmalloc memory on the fly

Posted on 2006-05-12
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Last Modified: 2013-12-16
I'm using linux to record DVB directly to disk. My problem is that  when Vmalloc fills up it freeze DVB driver. I need to find a way to empty that Vmalloc the fly. So far only solution is to reboot the server and it's not a good solution.

[root@refrecord ~]# cat /proc/meminfo
MemTotal:      2076108 kB
MemFree:       1965880 kB
Buffers:          8328 kB
Cached:          63164 kB
SwapCached:          0 kB
Active:          41336 kB
Inactive:        46100 kB
HighTotal:     1179596 kB
HighFree:      1094488 kB
LowTotal:       896512 kB
LowFree:        871392 kB
SwapTotal:     3068404 kB
SwapFree:      3068404 kB
Dirty:              28 kB
Writeback:           0 kB
Mapped:          28632 kB
Slab:             8788 kB
CommitLimit:   4106456 kB
Committed_AS:    88064 kB
PageTables:       1432 kB
VmallocTotal:   114680 kB
VmallocUsed:     21168 kB                              <--  when this fills up, it server will crash
VmallocChunk:    93008 kB
HugePages_Total:     0
HugePages_Free:      0
Hugepagesize:     4096 kB
[root@refrecord ~]#
[root@refrecord ~]# uname -a
Linux refrecord 2.6.16-1.2108_FC4 #1 Thu May 4 23:52:01 EDT 2006 i686 i686 i386 GNU/Linux


Please, any suggestion

-Jussi
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Question by:salmjuh
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4 Comments
 
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by:
ravenpl earned 252 total points
ID: 16668089
So far I know(but may be wrong) VmallocUsed never shrinks(it's only top marker of virtual memory space)
If it fills up, it may mean that Your kernel has a memory leak or want to use too much memory inside the kernel itself.
Do You happen to load third party kernel module? Sure it behaves OK.
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Assisted Solution

by:pjedmond
pjedmond earned 248 total points
ID: 16846019
Oooooh - this is baaaaaaaaddddd....!!!!!
As ravenpl has pointed out, VmallocUsed never goes down, and continued increase is most likely due to either a kernel memory leak or their being some very poorly written code that you are using for recording your DVB.

I notice that you are using FC4. FC is used to test 'bleeding edge' ideas. Can I suggest that you try a kernel rebuild without the 'cutting edge' capabilities:

http://www.digitalhermit.com/linux/Kernel-Build-HOWTO.html

Alternatively, try one of the RHEL clones:

Whitebox
CentOS

etc.

Their kernels only include the 'well tried and tested' elements in kernel, and shouldn't 'leak' as you seem to be experiencing.

HTH:)
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by:ravenpl
ID: 17167015
> Their kernels only include the 'well tried and tested' elements in kernel, and shouldn't 'leak' as you seem to be experiencing.
Started using RHEL43 - not really true. Many bugs that are already patched in vanilla(including some security flaws)
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Expert Comment

by:pjedmond
ID: 17168535
I'd also like to retract that statement as I'm now a little embarrassed by it. - Discovered that Xen is in there as well! - Hardly tried and tested. You have to ask yourself whether Redhat is now involved in 'feature' races with other distros! I think that a different ideology is now being used to develop the Redhat product.

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