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Date: Wed, 23 Mar 2011 21:18:02 +0300
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Subject: Re: ParNew (promotion failed)
From: ruslan usifov <ruslan.usifov@gmail.com>
To: user@cassandra.apache.org
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2011/3/23 Narendra Sharma <narendra.sharma@gmail.com>

> I think it is due to fragmentation in old gen, due to which survivor area
> cannot be moved to old gen. 300MB data size of memtable looks high for 3G
> heap. I learned that in memory overhead of memtable can be as high as 10x of
> memtable data size in memory. So either increase the heap or reduce the
> memtable thresholds further so that old gen gets freed up faster. With
> 16CFs, I would do both i.e. increase the heap to say 4GB and reduce memtable
> thresholds further.
>
>
> I think that you don't undestend me, 300MB is a summary thresholds on all
16 CF, so one memtable_threshold is about 18MB. Or all the same it is
necessary to reduce memtable_threshold?

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<br><br><div class=3D"gmail_quote">2011/3/23 Narendra Sharma <span dir=3D"l=
tr">&lt;<a href=3D"mailto:narendra.sharma@gmail.com">narendra.sharma@gmail.=
com</a>&gt;</span><br><blockquote class=3D"gmail_quote" style=3D"margin:0 0=
 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">
I think it is due to fragmentation in old gen, due to which survivor area c=
annot be moved to old gen. 300MB data size of memtable looks high for 3G he=
ap. I learned that in memory overhead of memtable can be as high as 10x of =
memtable data size in memory. So either increase the heap or reduce the mem=
table thresholds further so that old gen gets freed up faster. With 16CFs, =
I would do both i.e. increase the heap to say 4GB and reduce memtable thres=
holds further.<div>

<br></div><br></blockquote></div>I think that you don&#39;t undestend me, 3=
00MB is a summary thresholds on all 16 CF, so one memtable_threshold is abo=
ut 18MB. Or all the same it is necessary to reduce memtable_threshold?

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