Bug 465261 - [5.3][RFE] Copying of Vmcore Not Sparse Awareness
[5.3][RFE] Copying of Vmcore Not Sparse Awareness
Product: Red Hat Enterprise Linux 5
Classification: Red Hat
Component: kexec-tools (Show other bugs)
All Linux
low Severity low
: rc
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Assigned To: Neil Horman
Martin Jenner
Depends On:
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Reported: 2008-10-02 09:50 EDT by CAI Qian
Modified: 2008-10-02 10:44 EDT (History)
1 user (show)

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Doc Type: Bug Fix
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Last Closed: 2008-10-02 10:44:57 EDT
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Description CAI Qian 2008-10-02 09:50:42 EDT
Description of problem:
In Kdump initramfs, it uses busybox version of cp to save the vmcore to disk. However, it could not handle sparse file. If we could something similar to GNU version of cp's --sparse option, it could be a huge time and disk space saving. For example, in a SGI Altix IA64 machine,

it only take 3 minutes and 1.6G disk space for a 123G vmcore using GNU cp.

time cp --sparse=always /proc/vmcore vmcore.bcp.sp
[root@altix3 ~]# time cp --sparse=always /proc/vmcore vmcore.bcp.sp

real	3m1.078s
user	0m54.367s
sys	1m43.683s

[root@altix3 ~]# ls -lh vmcore.bcp.sp
-r-------- 1 root root 123G Oct  2 09:45 vmcore.bcp.sp
[root@altix3 ~]# du -sh vmcore.bcp.sp 
1.6G	vmcore.bcp.sp

Alternative, we could make busybox to be sparse awareness. It appears Ivana is the RHEL busybox maintainer. Ivana, please let us know if there is a plan to add sparse file support in the near future.

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How reproducible:
Comment 1 Neil Horman 2008-10-02 10:44:57 EDT
you can accomplish the same effect by specifying core_collector as makedumpfile -d 1

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