Re: [Yaffs] Percent usage affects write performance

Hi Charles,

I am also fcing the same problem.

I am thinking of following approaches to address this issue. Please correct
me if i am wrong

1. I tried the GC during SoftDeleteWorker context. 
    i.e, in the function "yaffs_SoftDeleteChunk" after incrementing the 
"softdeletion" parameter
    of the block information, call yaffs_CheckGarbageCollection

    I have tried this method to minimise the GC load during file write (i.e, 
the load on 
    yaffs_WriteChunkDataToObject)

2. While observed during Garbage Collection that, even if the pagesInUse of 
a block becomes ZERO
    (i.e, bi->pagesInUse - bi->softDeletions in " 
yaffs_FindBlockForGarbageCollection" function,), in 
    function   yaffs_GarbageCollectBlock, we are reading all the chunks and 
decrement the nDataChunks
    counter of the correcponding object. 

    I am just wondering is it possible to remove this overhead (reading all 
the chunks while the pagesInUse
    of that block is zero) by updating the nDataChunks counter while 
softDelete of the corresponding object,
   and erase the block directly while the pagesInUse of that block are zero.

Also i am wondering, will the above two approaches cause any abnormal
behaviour in any other context.

Thanks,
Asif

>On Friday 06 April 2007 04:53, Николай М. Виноградов
wrote:
>> Hello,
>>
>> I'm run into problem with yaffs2 usage.
>> When yaffs2 was only created(0% usage), I have write performance about
>> ~1Mb/sec.
>> When usage increased to 40-50%, I have only 450-500Kb/sec.
>> When usage increased to 95-99%, it's only 50-90Kb/sec. :-()
>>
>> My test is very simple, just copy 1Mb file from mem to yaffs2:
>> time cp /test.txt /usr/local
>>
>> /usr/local is yaffs2, / - is initramfs.
>>
>> Is there any reason for that? Maybe it's some GC related things and it's
>> normal behaviour?

> Yes it is GC causing this.
>
> Depending on how stuff is written to the fs, the GC sometimes has to work
much
> harder to get erased space to write.
>
> It seems the GC could do with some exploration to look for some
improvements.
>
> -- Charles


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