DMA in B2Test board?

[Owen Williams]

How do I install 299 on the main flash without an autoreinstallation
image?

owen


On Sat, 2007-03-10 at 12:46 -0500, Jim Gettys wrote:
> On Sat, 2007-03-10 at 22:58 +0545, Bipin Gautam wrote:
> > hello,
> > I experimented with various block size for file I/O. I experimented
> > with vfat and ext2 filesystem in the pen drive. 
> 
> Without specifications on the Pen drive, it's hard predict what would
> happen.  Write performance of file systems on flash depends on whether
> the block size of the file system matches well the underlying flash
> block size.
> 
> > i also experimented
> > with file write within nand storage; like
> > 
> > date
> > dd if=/dev/zero of=/testfile bs=6144 count=102400
> > date
> 
> On the NAND flash:
> 
> JFFS2 does data compression.
> 
> If you are writing zeros into a file, the actual write will extremely
> highly compressed, and so you are appending small writes to the log; to
> rewrite blocks on the log, you have to read the blocks, and might
> encounter errors.  This can have significant performance consequences,
> which I think are fixed in later builds.
> 
> 
> > 
> > The maximum preformance of XO nand storage (alone) was ~1.8 mb/sec
> > (jffs2) while the preformance of external usb drive is ~ 3-11 mb /sec
> > (at various block size)
> 
> Please install build 299, rather than 239.  There has been work on the
> NAND driver to highly optimize the error correction path in the NAND
> driver, which I believe was not in build 239, but IIRC, is in build 299.
> 
> So if you had NAND with errors, the error correction path was a possible
> source of CPU usage.  I believe the error correction code is now 100 or
> more times faster, courtesy of a community developer whose name slips my
> mind.
> 
> 
> > 
> > i thought 100% cpu use is because direct memory access(DMA) for disk
> > I/O has some problems (or disabled). Also, running  XO OS[1] in
> > virtual machine inside Parallels Workstation 2.2 with host OS xp sp2
> > shows the same problem of 100% cpu use during disk i/o
> > 
> > 
> > i cant give you a detailed stats. right now as my B2 OS is dead and
> > i'm downloading the latest build. (maybe tomorrow... if you want to
> > hear it)
> 
> Please install build 299.
> 
> > 
> > with regards,
> > -bipin
> > [1]olpc-redhat-stream-development-build-239-20070118_1416-devel_ext