[ENBD] 20G dd hang up!

[Kuniyasu SUZAKI]

Dear,

Excuse me for my late response. I don't have much time for ENBD now.

 >>From: "Peter T. Breuer" <ptb@it.uc3m.es>
 >>Subject: Re: [ENBD] 20G dd hang up!
 >>
 >>OK, well you are using kernel 2.2.18 which I haven't been testing on
 >>lately.  That kernel (the whole 2.2 series?) was one on which I had
 >>never been able to get some things such as request-merging working (by
 >>the way).  There may still be issues.  I simply don't know right now.
 >>All I can probably say about it is that I am no longer seriously testing
 >>on it, but that I _did_ test enbd 2.4.16 (not 16a) on it.  I think I

Is it ENDB 2.4.16 (not 2.4.26 :-) on kernl 2.2.* ?
If you have tested already, I will try it.

 >>would advise you to move up to the 2.4 series which I am beginning to
 >>seriously like from the performance point of view.  At best your results
 >>will be slow-ish on 2.2 kernels.

Unfortunately my applications run on 2.2.* kernel only. I would like
to keep to use 2.2.* kernel.

 >>I am pretty certain that there is no possible oops with the enbd
 >>kernel driver and the 2.4 series kernels, but for lack of testing I
 >>don't know precisely what the state is with respect to the 2.2 kernels.
 >>I "believe" that it compiles! Try and get some logs. A useful trick
 >>is to use the magic sysreq facilty to put all kernel messages on the 
 >>console. It's either sysreq-0 or sysreq-9. I forget which.

 >>May I ask what compiler you compiled with? gcc 2.7.3 2.81 2.91 2.95 2.96
 >>3.03..?

I used gcc version egcs-2.91.66 19990314/Linux (egcs-1.1.2 release).

 >>And did you compile for SMP or not (it doesn't matter, I just want to
 >>know just in case the answer tells me something I didn't expect).

The host machine is SMP but I used it Single CPU Linux kernel on it.
Because I don't want to be involved in SMP trouble.

 >>Well, in fact you have performed a very interesting experiment. I have
 >>not stress tested the 2.4.16 code on kernel 2.2.18. I think you should
 >>tell me what your test is.

Yes. The contribution is my pleasure.

 >>Can you pick up the "nbd-test" utility from the nbd-2.4.27pre1 code
 >>(it's a slightly more tuned version of dd) and tell be the result of:
 >>   writing memory in 1024 blocks for twice the size of ram with it
 >>that should be something like
 >>   nbd-test -b 1024 -s blah_in_bytes -t 1:2 /dev/nda

OK. I will try the "nbd-test" for nbd-2.4.27pre1 on nbd-2.4.26.

 >>Personally, I think you're stuck with some kind of unknowable memory
 >>deadlock under 2.2.18 (between tcp and other resources). I am most
 >>surprised ... tell me, can you slow down the processor on your TP?

Is it a bug on 2.2.18? Do you think that the problem is solved on 2.4.*?
Should I move to other 2.2.* kernel?

  Kuniyasu SUZAKI, National Institute of Advanced Industrial Science and Technology,
  Tsukuba Central 2, Umezono 1-1-1, Tsukuba, Ibaraki 305-8568, JAPAN
  Project NTC (Network Transferable Computer) http://www.etl.go.jp/~suzaki/English/NTC