Re: Memory usage of the machine with ES is continuously increasing

[Pradeep Reddy]

I have straced elasticsearch for a couple of minutes
strace -fp PID -o file.txt

out of the 40k+ events recorded
2.2k + events have resulted in errors like this
https://gist.github.com/vanga/55ca296f737b3c1fb9a2

I think this is the reason for the dentry bloating, though I am not sure if 
there is some thing wrong with my cluster or not.

On Monday, May 4, 2015 at 4:17:40 PM UTC+5:30, Pradeep Reddy wrote:
>
> ES version 1.5.2
> Arch Linux on Amazon EC2
> of the available 16 GB, 8 GB is heap (mlocked). Memory consumption is 
> continuously increasing (225 MB per day). 
> Total no of documents is around 800k, 500 MB. 
>
> cat /proc/meminfo has 
>>
>> Slab: 3424728 kB 
>
> SReclaimable: 3407256 kB
>>
>
>  
>
> curl -XGET 'http://localhost:9200/_nodes/stats/jvm?pretty' 
>>
>> "heap_used_in_bytes" : 5788779888,
>>   "heap_used_percent" : 67,
>>   "heap_committed_in_bytes" : 8555069440,
>>
>>
> slabtop
>  OBJS ACTIVE  USE OBJ SIZE  SLABS OBJ/SLAB CACHE SIZE 
> NAME   
> 17750313 17750313 100%0.19K 845253   21   3381012K dentry
>  
>
> So the continuous increase in memory usage is because of the slab usage I 
> think, If I restart ES, then slab memory is freed. I see that ES still has 
> some free heap available, but from elastic documentation  
>
>> Lucene is designed to leverage the underlying OS for caching in-memory 
>> data structures. Lucene segments are stored in individual files. Because 
>> segments are immutable, these files never change. This makes them very 
>> cache friendly, and the underlying OS will happily keep hot segments 
>> resident in memory for faster access.
>>
>
> My question is, should I add more nodes or increase the ram of each node 
> to let lucene use as much memory as it wants ? how significant performance 
> difference will be there if I choose to upgrade ES machines to have more 
> RAM. 
>
> Or, can I make some optimizations that decreases the slab usage or clean 
> slab memory partially?
>
>
>

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Re: Memory usage of the machine with ES is continuously increasing

[Pradeep Reddy]

Actually, the problem has appeared again, memory consumption was stable for 
couple of days, then it started increasing, env variable was only set for 
that particular session or something, I had to set it again by adding it to 
/etc/environment , but this doesn't have any affect anymore.. there may be 
some other parameter that's affecting the dentry cache.


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Re: Memory usage of the machine with ES is continuously increasing

[Pradeep Reddy]

So the bloating of dentry cache is because of this 
https://bugzilla.redhat.com/show_bug.cgi?id=1044666 
My NSS version is 3.18 (Arch Linux, Kernel version. 3.14.21)

Setting NSS_SDB_USE_CACHE=YES has stopped the bloating. I have set this on 
one of the three nodes, dentry size hasn't changed a bit (in fact there was 
a small decrease) where as other two nodes have an increase of around 200 
MB (in 18 hours).

At this point I am not sure which component of th ES is making these curl 
requests (may be cloud-aws plugin?)

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Re: Memory usage of the machine with ES is continuously increasing

[Pradeep Reddy]

So the bloating of dentry cache is because of this 
https://bugzilla.redhat.com/show_bug.cgi?id=1044666 
My NSS version is 3.18 (Arch Linux, Kernel version. 3.14.21)

Setting NSS_SDB_USE_CACHE=YES has stopped the bloating. I have set this on 
one of the three nodes, dentry size hasn't changed a bit (in fact there was 
a small decrease) where as other two nodes have an increase of around 200 
MB (in 18 hours).

At this point I am not sure which component of th ES is making these curl 
requests (may be cloud-aws plugin?)

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Re: Memory usage of the machine with ES is continuously increasing

[Pradeep Reddy]

Thanks Jörg,

Yes it is unusual to have such dentry cache, there is definitely something
fishy going on. Stopping ES clears it up, so it is something related ES I
believe.

On Thu, May 7, 2015 at 8:16 PM, joergpra...@gmail.com  wrote:

> On my systems, dentry use is ~18MB while ES 1.5.2 is under heavy duty
> (RHEL 6.6, Java 8u45, on-premise server).
>
> I think you should double check if the effect you see is caused by ES or
> by your JVM/Arch Linux/EC2/whatever.
>
> Jörg
>
> On Mon, May 4, 2015 at 12:47 PM, Pradeep Reddy <
> pradeepreddy.manu.iit...@gmail.com> wrote:
>
>> ES version 1.5.2
>> Arch Linux on Amazon EC2
>> of the available 16 GB, 8 GB is heap (mlocked). Memory consumption is
>> continuously increasing (225 MB per day).
>> Total no of documents is around 800k, 500 MB.
>>
>> cat /proc/meminfo has
>>>
>>> Slab: 3424728 kB
>>
>> SReclaimable: 3407256 kB
>>>
>>
>>
>>
>> curl -XGET 'http://localhost:9200/_nodes/stats/jvm?pretty'
>>>
>>> "heap_used_in_bytes" : 5788779888,
>>>   "heap_used_percent" : 67,
>>>   "heap_committed_in_bytes" : 8555069440,
>>>
>>>
>> slabtop
>>  OBJS ACTIVE  USE OBJ SIZE  SLABS OBJ/SLAB CACHE SIZE
>> NAME
>> 17750313 17750313 100%0.19K 845253   21   3381012K dentry
>>
>>
>> So the continuous increase in memory usage is because of the slab usage I
>> think, If I restart ES, then slab memory is freed. I see that ES still has
>> some free heap available, but from elastic documentation
>>
>>> Lucene is designed to leverage the underlying OS for caching in-memory
>>> data structures. Lucene segments are stored in individual files. Because
>>> segments are immutable, these files never change. This makes them very
>>> cache friendly, and the underlying OS will happily keep hot segments
>>> resident in memory for faster access.
>>>
>>
>> My question is, should I add more nodes or increase the ram of each node
>> to let lucene use as much memory as it wants ? how significant performance
>> difference will be there if I choose to upgrade ES machines to have more
>> RAM.
>>
>> Or, can I make some optimizations that decreases the slab usage or clean
>> slab memory partially?
>>
>>
>>  --
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>> "elasticsearch" group.
>> To unsubscribe from this group and stop receiving emails from it, send an
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>> 
>> .
>> For more options, visit https://groups.google.com/d/optout.
>>
>
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Re: Memory usage of the machine with ES is continuously increasing

[joergpra...@gmail.com]

On my systems, dentry use is ~18MB while ES 1.5.2 is under heavy duty (RHEL
6.6, Java 8u45, on-premise server).

I think you should double check if the effect you see is caused by ES or by
your JVM/Arch Linux/EC2/whatever.

Jörg

On Mon, May 4, 2015 at 12:47 PM, Pradeep Reddy <
pradeepreddy.manu.iit...@gmail.com> wrote:

> ES version 1.5.2
> Arch Linux on Amazon EC2
> of the available 16 GB, 8 GB is heap (mlocked). Memory consumption is
> continuously increasing (225 MB per day).
> Total no of documents is around 800k, 500 MB.
>
> cat /proc/meminfo has
>>
>> Slab: 3424728 kB
>
> SReclaimable: 3407256 kB
>>
>
>
>
> curl -XGET 'http://localhost:9200/_nodes/stats/jvm?pretty'
>>
>> "heap_used_in_bytes" : 5788779888,
>>   "heap_used_percent" : 67,
>>   "heap_committed_in_bytes" : 8555069440,
>>
>>
> slabtop
>  OBJS ACTIVE  USE OBJ SIZE  SLABS OBJ/SLAB CACHE SIZE
> NAME
> 17750313 17750313 100%0.19K 845253   21   3381012K dentry
>
>
> So the continuous increase in memory usage is because of the slab usage I
> think, If I restart ES, then slab memory is freed. I see that ES still has
> some free heap available, but from elastic documentation
>
>> Lucene is designed to leverage the underlying OS for caching in-memory
>> data structures. Lucene segments are stored in individual files. Because
>> segments are immutable, these files never change. This makes them very
>> cache friendly, and the underlying OS will happily keep hot segments
>> resident in memory for faster access.
>>
>
> My question is, should I add more nodes or increase the ram of each node
> to let lucene use as much memory as it wants ? how significant performance
> difference will be there if I choose to upgrade ES machines to have more
> RAM.
>
> Or, can I make some optimizations that decreases the slab usage or clean
> slab memory partially?
>
>
>  --
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> 
> .
> For more options, visit https://groups.google.com/d/optout.
>

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Re: Memory usage of the machine with ES is continuously increasing

[Pradeep Reddy]

Hi Mark,

Thanks.

I understand that caching makes ES perform better, and it's normal. What I 
don't understand is the unusual size of dentry objects (dentry size 
increase at about 200+ mb per day?) for the data size I have. There isn't 
this behaviour on the ELK ES where I have many times of data compared to 
this. 

Does that mean there are unusual no of segments being created?, is there 
something that needs to be optimized? 

The only thing that is different is that we take hourly snapshots to S3 
directly, is it possible that the S3 paths are also part of dentry objects? 
is it possible that the no of snapshots has some thing to do with? (I know 
that having too many no of snapshots will make snapshotting slower). Note 
that when I restart the ES it gets cleared(most of it, may be OS clears up 
this cache once it sees that the parent process has been stopped).


On Monday, May 4, 2015 at 4:17:40 PM UTC+5:30, Pradeep Reddy wrote:
>
> ES version 1.5.2
> Arch Linux on Amazon EC2
> of the available 16 GB, 8 GB is heap (mlocked). Memory consumption is 
> continuously increasing (225 MB per day). 
> Total no of documents is around 800k, 500 MB. 
>
> cat /proc/meminfo has 
>>
>> Slab: 3424728 kB 
>
> SReclaimable: 3407256 kB
>>
>
>  
>
> curl -XGET 'http://localhost:9200/_nodes/stats/jvm?pretty' 
>>
>> "heap_used_in_bytes" : 5788779888,
>>   "heap_used_percent" : 67,
>>   "heap_committed_in_bytes" : 8555069440,
>>
>>
> slabtop
>  OBJS ACTIVE  USE OBJ SIZE  SLABS OBJ/SLAB CACHE SIZE 
> NAME   
> 17750313 17750313 100%0.19K 845253   21   3381012K dentry
>  
>
> So the continuous increase in memory usage is because of the slab usage I 
> think, If I restart ES, then slab memory is freed. I see that ES still has 
> some free heap available, but from elastic documentation  
>
>> Lucene is designed to leverage the underlying OS for caching in-memory 
>> data structures. Lucene segments are stored in individual files. Because 
>> segments are immutable, these files never change. This makes them very 
>> cache friendly, and the underlying OS will happily keep hot segments 
>> resident in memory for faster access.
>>
>
> My question is, should I add more nodes or increase the ram of each node 
> to let lucene use as much memory as it wants ? how significant performance 
> difference will be there if I choose to upgrade ES machines to have more 
> RAM. 
>
> Or, can I make some optimizations that decreases the slab usage or clean 
> slab memory partially?
>
>
>

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Re: Memory usage of the machine with ES is continuously increasing

[Mark Walkom]

When the underlying lucene engine interacts with a segment the OS will
leverage free system RAM and keep that segment in memory. However
Elasticsearch/lucene has no way to control of OS level caches.

What exactly is the problem here? This caching is what helps provide
performance for ES.
​

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Re: Memory usage of the machine with ES is continuously increasing

[Pradeep Reddy]

ES version was actually 1.5.0, I have upgraded to 1.5.2, so restarting the 
ES cleared up the dentry cache.
I believe dentry cache is something that is handled by linux, but it seems 
like ES/lucene has a role to play how dentry cache is handled. If that is 
the case ES/lucene should be able to control how much dentry cache is there.

Dentry cache is continuously increasing, is this unavoidable considering 
that the data is increasing every day (though not significant) ? I have an 
ELK stack where there are many millions of documents, though there are less 
search requests to the cluster, which doesn't have this problem.

On Monday, May 4, 2015 at 4:17:40 PM UTC+5:30, Pradeep Reddy wrote:
>
> ES version 1.5.2
> Arch Linux on Amazon EC2
> of the available 16 GB, 8 GB is heap (mlocked). Memory consumption is 
> continuously increasing (225 MB per day). 
> Total no of documents is around 800k, 500 MB. 
>
> cat /proc/meminfo has 
>>
>> Slab: 3424728 kB 
>
> SReclaimable: 3407256 kB
>>
>
>  
>
> curl -XGET 'http://localhost:9200/_nodes/stats/jvm?pretty' 
>>
>> "heap_used_in_bytes" : 5788779888,
>>   "heap_used_percent" : 67,
>>   "heap_committed_in_bytes" : 8555069440,
>>
>>
> slabtop
>  OBJS ACTIVE  USE OBJ SIZE  SLABS OBJ/SLAB CACHE SIZE 
> NAME   
> 17750313 17750313 100%0.19K 845253   21   3381012K dentry
>  
>
> So the continuous increase in memory usage is because of the slab usage I 
> think, If I restart ES, then slab memory is freed. I see that ES still has 
> some free heap available, but from elastic documentation  
>
>> Lucene is designed to leverage the underlying OS for caching in-memory 
>> data structures. Lucene segments are stored in individual files. Because 
>> segments are immutable, these files never change. This makes them very 
>> cache friendly, and the underlying OS will happily keep hot segments 
>> resident in memory for faster access.
>>
>
> My question is, should I add more nodes or increase the ram of each node 
> to let lucene use as much memory as it wants ? how significant performance 
> difference will be there if I choose to upgrade ES machines to have more 
> RAM. 
>
> Or, can I make some optimizations that decreases the slab usage or clean 
> slab memory partially?
>
>
>

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