Nate Diller wrote:
On 8/6/06, rvalles <[EMAIL PROTECTED]> wrote:
The bug is as I've explained a thousand times. (and it does only affect
kernels newer than 2.6.12, all of them, that's one thing I'm sure)
Newer kernels have a nice feature called "blktrace" to trace the block
layer activity. I include with this mail a log of the whole block (this
time it was just about 30 seconds, the previous one, when I was sending
a mail to a maillist, it was 10 minutes or maybe more).
How did I do it:
- Write a mail to myself (small mail, btw).
- Start the btrace.
- Send it. (I pressed 'y' at mutt mail sending screen)
- Look at the HD led.
- When it stopped, the crap @ btrace stopped too. I then stopped btrace.
I hope that this log helps enlighten someone.
Now, to add to the data about the bug:
- My new desktop uses reiser4. It is affected, too.
- Just by typing "reboot" at my old desktop, the bug triggers inmediatly
after the wall message is sent, and lasts about 10 minutes.
- Latest reiser4 fsck was run with --build-fs on my old desktop the day
before; The FS had got, before that, some corrupcion (probably a bug)
that caused kernel panics, so the FS is quite clean now, yet I can
reproduce the bugs.
I will be happy to help further in any way.
I also have many friends who use reiser4 and are experiencing it; it
would be a shame if reiser4 finally got merged into the kernel with
this bug still there.
91% of the requests are 4K in size, 77% of requests are write
barriers. looks like there's something that causes bitmap blocks to
be written synchronously.
there's also a LOT of duplication, blocks that are written and then
immediately RE-written. the 4k block at sector 23246207 is written
226 times over the course of this trace, each time seemingly in a pair
(write it, rewrite it, do other stuff, write it, re-write it, etc).
this is pathological behavior, it's a real bug even without the
performance loss.
NATE
I hope no-one says reiser4 is "2 times faster than ext3" before this
issue is cleared.
Could some developer (if Nate's one, pardon me) comment on this issue?
It seems to me
much more important than that endless thread about "official point of view".
Incidentally, I've witnessed similar behaviour in various simple tasks,
e.g. writing
entries to an sqlite database, or receiving mail from pop3 in thunderbird.
On kernel-2.6.17.7 currently.
--vk
