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

[Dave Kleikamp]

On 06/26/2018 10:40 AM, David Wysochanski wrote:
> On Tue, 2018-06-26 at 11:27 -0400, Dave Anderson wrote:
>>
>> ----- 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...
>>
> 
> Do you see any advantage to keeping the hash table for loop detection
> or would you accept a patch that removes it completely in favor of a
> another algorithm?

Could the same algorithm be modified so that it can slow down after a
certain number of list members, say maybe saving only every 10th element
to the hash (but checking every new one)?