[Crash-utility] crash-7.3.2 very long list iteration progressively increasing memory usage

[Dave Anderson]

----- Original Message -----
> On Tue, 2018-06-26 at 15:34 +0100, Jeremy Harris wrote:
> > On 06/26/2018 03:29 PM, David Wysochanski wrote:
> > > On Tue, 2018-06-26 at 09:21 -0400, Dave Anderson wrote:
> > > > Yes, by default all list entries encountered are put in the built-in
> > > > hash queue, specifically for the purpose of determining whether there
> > > > are duplicate entries.  So if it's still running, it hasn't found any.
> > > > 
> > > > To avoid the use of the hashing feature, try entering "set hash off"
> > > > before kicking off the command.  But of course if it finds any, it
> > > > will loop forever.
> > > > 
> > > 
> > > Ah ok yeah I forgot about the built-in list loop detection!
> > 
> > For a storage-less method of list loop-detection: run two walkers
> > down the list, advancing two versus one elements.  If you ever
> > match the same element location after starting, you have a loop.
> 
> I agree some algorithm [1] without a hash table may be better
> especially for larger lists.

I'll await your patch...

> 
> I also found that ctrl-c of the very long running crash list command
> did not release the hash table memory - I had to exit crash for that.

Right, just as in any case where malloc() is used, the freed memory is not
removed the user address space, but remains for subsequent allocations.

Dave


> 
> [1] https://en.wikipedia.org/wiki/Cycle_detection
> 
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