On 05/12/13 23:36, Charles Manning wrote:
>
>
>
> On Fri, Dec 6, 2013 at 9:30 AM, Dominic Raferd 
> <dominic@timedicer.co.uk <mailto:dominic@timedicer.co.uk>> wrote:
>
>     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
>
>
>
> I only used the 1-byte file as an extreme example for illustration.
>
> Your system has 2k pages. If you have 1k files then each will be using 
> 4k of space.
> If you have 2.5k files, then each will be using 6 k of space.
>
> The overhead goes down as the file size goes up.
>
> What does find give you for file sizes of 1000, 2000, 4000?
>
> -- Charles
>

Thanks again for your response.

root@G-124:~# find /tmp/mnt/mtdblock1 -size -1000c|wc -l
518
root@G-124:~# find /tmp/mnt/mtdblock1 -size -2000c|wc -l
784
root@G-124:~# find /tmp/mnt/mtdblock1 -size -4000c|wc -l
1095
root@G-124:~# find /tmp/mnt/mtdblock1|wc -l
1599

But one curious thing is that there is now a little more space available 
than there was before (99% full -> 97% full). In case this is because of 
something that YAFFS has been doing I give the now-current yaffs file:

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..... 97900
nFreeTnodes........ 346
nObjectsCreated.... 96700
nFreeObjects....... 104
nFreeChunks........ 7339
nPageWrites........ 367200
nPageReads......... 2186391
nBlockErasures..... 5792
nGCCopies.......... 338725
garbageCollections. 5681
passiveGCs......... 2
nRetriedWrites..... 0
nShortOpCaches..... 10
nRetireBlocks...... 0
eccFixed........... 0
eccUnfixed......... 0
tagsEccFixed....... 0
tagsEccUnfixed..... 0
cacheHits.......... 3412
nDeletedFiles...... 0
nUnlinkedFiles..... 1130
nBackgroudDeletions 0
useNANDECC......... 1
noTagsECC.......... 0
isYaffs2........... 1
inbandTags......... 0
emptyLostAndFound.. 0
disableLazyLoad.... 0