[stgt] help tgt segfault

Tomasz Chmielewski mangoo at wpkg.org
Tue Feb 3 11:46:35 CET 2009

FUJITA Tomonori schrieb:


>>> 2) you use slow network in this configuration, as you said before?
>> Yes.
>> Slow connection is just 5 kB/s in both directions.
>> It's easy to reproduce the problem this way.
>> Slow link is the third target above.
> So the connections between the target box and are slow
> while the connections between the target box and is
> not slow.
> Right?

Yes, it is correct.
But I'm sure the same will happen with only one target connected (using 
a slow link).

>>> 3) All your bug reports about this problem happened in this
>>> configuration? If not, please tell me about the other configuration.
>> In "real life" it happens under slightly different (more complex, harder to set up) conditions:
>> - tgtd uses DRBD resource as the block device (backing store)
>> - link is about 100 kB/s (writes; DRBD replication over a slow internet connection) and fast local HDD IO (reads)
>> - when DRBD exchanges bitmaps with the remote peer, it suspends IO for several seconds
> The problem might be related with TMF.
>> - more targets configured, more initiators connected
> Hmm, just with lots of initiators? Even with decent link speed and no
> suspended I/Os?

_And_ with DRBD and slow link.
With lots of initiators and decent speed link, no suspended IOs, it 
behaves stable.

> I'm not sure about what 'more targets configured' mean.

I mean that "tgtadm --op show --mode target" will output 40-50 targets.
4-5 initiators connected to each target.
But I think it's not relevant, as these segfaults don't relate to the
number of initiators or targets.

Tomasz Chmielewski

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