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Re: Bug report - yours or mine?

On Apr 04, 2002  18:21 +0100, Declan Moriarty wrote:
> I have 2 large partitions on /dev/hdb for linux which are now ext3. Before 
> the conversion, and still with a 2.4.3 kernel (not ext3 capable) 
> hdparm -tT reutrns 37MB/sec & 10.5 MB/sec respectively; 
> After converting as per the mini howto (Using defaults), and updating the 
> kernel to 2.4.18, hdparm -tT returns 37MB/sec and 6.5MB/sec.

That is purely a 2.4.3 -> 2.4.18 kernel issue.  hdparm has nothing to do
with the filesystem (it is communicating with the IDE hardware directly).

> What's worse, in a console, I get this error repeated many times
> invalidate: busy buffer

That is because hdparm is probably calling the "BLKFLSBUF" ioctl, which
is trying to flush dirty buffers from the system to ensure an accurate
test.  Ext3 (and also ext2, reiserfs, ...) keeps some buffers on the
device in-use while the filesystem is mounted, so it is not possible to
flush them at all.  In 2.4.3 kernels it silently ignored such busy
buffers.  In 2.4.18 it prints a warning, but the behaviour is the same.

> in an X terminal, I don't see it at all, although the speeds are similar.

That's because this is a kernel message and not output from hdparm, so it
will only be sent to the console.  You can also see it in your syslog or
in dmesg output.

> Is this dodgy hardware, kernel, or what?


> Please copy me direct - I'm not subscribed to this list yet - inbox blues. 
> hdparm -d1 refuses to set dma
> [root genius /root]# hdparm -d1 /dev/hdb
> /dev/hdb:
>  setting using_dma to 1 (on)
>  HDIO_SET_DMA failed: Operation not permitted
>  using_dma    =  0 (off)

This is the real speed issue.  You probably need to compile your kernel
with the appropriate PCI IDE chipset support enabled to get DMA.  It
may be that you need to use an -ac kernel (which has Andre Hedrick's
IDE patches in it) to get full DMA support for your chipset.

Cheers, Andreas
Andreas Dilger  \ "If a man ate a pound of pasta and a pound of antipasto,
                 \  would they cancel out, leaving him still hungry?"
http://www-mddsp.enel.ucalgary.ca/People/adilger/               -- Dogbert

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