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Posted to common-user@hadoop.apache.org by Nathan Marz <na...@rapleaf.com> on 2009/03/04 00:25:33 UTC
Mappers become less utilized as time goes on?
I'm seeing some really bizarre behavior from Hadoop 0.19.1. I have a
fairly large job with about 29000 map tasks and 72 reducers. there are
304 map task slots in the cluster. When the job starts, it runs 304
map tasks at a time. As time goes on the number of map tasks run
concurrently drops. For at least half of the execution exactly 152
mappers were run at a time. Towards, the end , when there were only
100 or so tasks remaining, the number of concurrent mappers quickly
fell to 2 at a time, bringing the end of the map phase to a crawl.
This was the only job running on the cluster. Has anyone else seen
behavior like this?
Re: Mappers become less utilized as time goes on?
Posted by Pedro Vivancos <pe...@vocali.net>.
I have the same problem... Please let me know if you solve it and how to.
Thanks.
On Wed, Mar 4, 2009 at 2:49 AM, Nathan Marz <na...@rapleaf.com> wrote:
> Nope... and there were no failed tasks.
>
>
>
> On Mar 3, 2009, at 5:16 PM, Runping Qi wrote:
>
> Were task Trackers black-listed?
>>
>>
>> On Tue, Mar 3, 2009 at 3:25 PM, Nathan Marz <na...@rapleaf.com> wrote:
>>
>> I'm seeing some really bizarre behavior from Hadoop 0.19.1. I have a
>>> fairly
>>> large job with about 29000 map tasks and 72 reducers. there are 304 map
>>> task
>>> slots in the cluster. When the job starts, it runs 304 map tasks at a
>>> time.
>>> As time goes on the number of map tasks run concurrently drops. For at
>>> least
>>> half of the execution exactly 152 mappers were run at a time. Towards,
>>> the
>>> end , when there were only 100 or so tasks remaining, the number of
>>> concurrent mappers quickly fell to 2 at a time, bringing the end of the
>>> map
>>> phase to a crawl. This was the only job running on the cluster. Has
>>> anyone
>>> else seen behavior like this?
>>>
>>>
>>>
>
Re: Mappers become less utilized as time goes on?
Posted by Nathan Marz <na...@rapleaf.com>.
Nope... and there were no failed tasks.
On Mar 3, 2009, at 5:16 PM, Runping Qi wrote:
> Were task Trackers black-listed?
>
>
> On Tue, Mar 3, 2009 at 3:25 PM, Nathan Marz <na...@rapleaf.com>
> wrote:
>
>> I'm seeing some really bizarre behavior from Hadoop 0.19.1. I have
>> a fairly
>> large job with about 29000 map tasks and 72 reducers. there are 304
>> map task
>> slots in the cluster. When the job starts, it runs 304 map tasks at
>> a time.
>> As time goes on the number of map tasks run concurrently drops. For
>> at least
>> half of the execution exactly 152 mappers were run at a time.
>> Towards, the
>> end , when there were only 100 or so tasks remaining, the number of
>> concurrent mappers quickly fell to 2 at a time, bringing the end of
>> the map
>> phase to a crawl. This was the only job running on the cluster. Has
>> anyone
>> else seen behavior like this?
>>
>>
Re: Mappers become less utilized as time goes on?
Posted by Runping Qi <ru...@gmail.com>.
Were task Trackers black-listed?
On Tue, Mar 3, 2009 at 3:25 PM, Nathan Marz <na...@rapleaf.com> wrote:
> I'm seeing some really bizarre behavior from Hadoop 0.19.1. I have a fairly
> large job with about 29000 map tasks and 72 reducers. there are 304 map task
> slots in the cluster. When the job starts, it runs 304 map tasks at a time.
> As time goes on the number of map tasks run concurrently drops. For at least
> half of the execution exactly 152 mappers were run at a time. Towards, the
> end , when there were only 100 or so tasks remaining, the number of
> concurrent mappers quickly fell to 2 at a time, bringing the end of the map
> phase to a crawl. This was the only job running on the cluster. Has anyone
> else seen behavior like this?
>
>