On 05/12/13 18:46, Charles Manning wrote:
> On Friday 06 December 2013 01:27:09 Dominic Raferd wrote:
>> I am responsible for a PBX system which uses embedded uClinux on 256MB
>> internal memory disk, this uses YAFFS2 filesystem and it is rapidly running
>> out of memory. df used space is 240MB (96% of total) and du used space is
>> 76MB. Once df gets to 100% used I guess the whole system will fail and be
>> irrecoverable. I don't understand much about YAFFS but here is some info:
>>
>> root@G-124:~# cat /proc/yaffs
>> YAFFS built:Apr 22 2010 11:02:12
>> $Id: yaffs_fs.c,v 1.89 2009-11-29 21:50:10 charles Exp $
>> $Id: yaffs_guts.c,v 1.98 2009-12-07 01:17:33 charles Exp $
>>
>>
>> Device 0 "file system"
>> startBlock......... 0
>> endBlock........... 1951
>> totalBytesPerChunk. 2048
>> nDataBytesPerChunk. 2048
>> chunkGroupBits..... 0
>> chunkGroupSize..... 1
>> nErasedBlocks...... 63
>> nReservedBlocks.... 5
>> blocksInCheckpoint. 0
>> nTnodesCreated..... 97500
>> nFreeTnodes........ 41
>> nObjectsCreated.... 96700
>> nFreeObjects....... 92
>> nFreeChunks........ 8822
>> nPageWrites........ 8033
>> nPageReads......... 89169
>> nBlockErasures..... 180
>> nGCCopies.......... 4471
>> garbageCollections. 72
>> passiveGCs......... 0
>> nRetriedWrites..... 0
>> nShortOpCaches..... 10
>> nRetireBlocks...... 0
>> eccFixed........... 0
>> eccUnfixed......... 0
>> tagsEccFixed....... 0
>> tagsEccUnfixed..... 0
>> cacheHits.......... 20
>> nDeletedFiles...... 0
>> nUnlinkedFiles..... 56
>> nBackgroudDeletions 0
>> useNANDECC......... 1
>> noTagsECC.......... 0
>> isYaffs2........... 1
>> inbandTags......... 0
>> emptyLostAndFound.. 0
>> disableLazyLoad.... 0
>>
>> (The mounting memory loss may be related to frequent power cuts. Is there
>> anything that can be done to recover the lost memory (currently 164MB)
>> before the system fails entirely?
>>
>> I would be very grateful for some urgent help/input, and can pay something
>> for a positive resolution. (The PBX box also has an attached USB drive
>> (8GB) but although this is working fine I don't believe the system can boot
>> from here, and it has no local interface, only via ethernet.)
> Hello Dominic
>
> If you have a wide disparity between du and df this typically means that you
> have lots of small files.
>
> du just adds up file contents and such to estimate space used with no
> knowledge of file system layout. It makes various guesses. df asks the file
> system what space is in use so that is a more accurate value.
>
> If you store a 1-byte file in Yaffs you will end up with:
> 1x object header chunk + 1x data chunk = 2 chunks = 4k on your system.
>
> However that overhead is fixed, so if you have a 1MB file, it just takes up
> 1MB + 1x object header chunk = 1MB + 2048 bytes.
>
> So... what are you storing that you can get rid of?
>
>
Thanks for the response Charles. But there are very few small files in
this system. If I mount this boot device at /tmp/mnt/mtdblock1:
# find /tmp/mnt/mtdblock1 -size -10c|wc -l
87
# find /tmp/mnt/mtdblock1 -size -100c|wc -l
281
(text/plain)