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To: "xfs@xxxxxxxxxxx" <xfs@xxxxxxxxxxx>
Subject: XFS_DB
From: Anshul Kundra <anshul.kundra@xxxxxxx>
Date: Wed, 20 Feb 2013 17:11:18 +0000
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Thread-index: Ac4PiZVHlISWMOUBSoqggnsthpoQ1A==
Thread-topic: XFS_DB



I have system with configuration as

RAM : 4G



On  this system I had created an XFS file system of size 250 GB, I am using xfs_db utility to  get file mapping( file name and inode number ) information using the daddr & corresponding  File system block number.  


/dev/sdd1 : 250G filesystem, 13% (29 G) full, aprox 3.5 million files


Steps executed in getting this information is as below :


test#  xfs_db -i -c "convert daddr 6612146 fsb" /dev/sdd1

0xc9c96 (826518)

test:~ #  xfs_db -i -c "blockget -n -b 826518" /dev/sdd1

xfs_db: out of memory


Utility (xfs_db ) is giving OOM in extracting  block information using “blockget” and in some cases it gives OOM when subcommand “ncheck”of xfs_db.  It is mentioned in the manuals itself that ncheck is memory consuming command. When we analysed the command memory map of ncheck using “pmap”  most of the memory is consumed in heap. It’s not utilized by cache memory.



Whether xfs_db stores  information of all the blocks  upto the requested block or it maintains its internal structure. When checking the xfs_db codethen found function call like (push_cur()  etc ) whether it is maintaining its own command execution stack.


Instead of accessing the device itself can we read the metadump file to get the required information of file mapping with file system block number. Its binary file but is there any utility which reads the metadump file itself instead of file system image. As it is easier to read the metadump file instead of go towards  disk access itself. There is file obfuscation in the file name for 4 characters


Whether reading metadump file for getting file mapping with file system block number still consumes same amount of memory or this will not works.


Please provide some reference to either eliminate the OOM (in blockget and ncheck) or any other way either related to accessing metadump file in getting the mapping (fsbno to file name or inode number ). As currently finding out the cause of this memory consumption from the source itself whether optimization in finding this mapping information  is possible or not  


On finding out solution over the OOM I found reference of xfs_db 64  but there is no 64 bit version of utility available in xfs website either there will be some configuration option or it becomes obsolete.




Thanks & Best Regards

Anshul Kundra




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