Re: Is Solr cache cleared when I restart Solr?

[Zheng Lin Edwin Yeo]

I did change the JVM heap size from 16GB to 24GB. Will that make a
difference?

Regards,
Edwin

On 28 January 2016 at 22:10, Alessandro Benedetti 
wrote:

> As already specified you need to distinguish between Solr Cache and OS
> Memory mapped files.
> What you should clearly notice in your situation is an increase of space
> for the OS Memory mapped files.
> Which means faster access to index segments ( almost all the different data
> structures are memory mapped ).
>
> Related the internal Solr Cache, if you haven't changed the java memory
> properties, I would expect not that much difference.
> If you were on a virtual machine sharing physical memory with other virtual
> instances, you could find benefits on the other hand.
>
> Cheers
>
>
> On 28 January 2016 at 05:44, Zheng Lin Edwin Yeo 
> wrote:
>
> > Thanks Erick and Shawn for your reply.
> >
> > We have recently upgraded the server RAM from 64MB to 192MB, and I
> noticed
> > that this caching occurs after we upgraded the RAM. Previously, the cache
> > may not even be preserved in the same Solr session.
> > So is it true that the upgrading of the server RAM creates enough spare
> > memory for good caching?
> >
> > Regards,
> > Edwin
> >
> >
> > On 28 January 2016 at 12:27, Shawn Heisey  wrote:
> >
> > > On 1/27/2016 8:11 PM, Zheng Lin Edwin Yeo wrote:
> > > > I would like to find out, is the cache in the Solr cleared when I
> shut
> > > down
> > > > the Solr instant and restart it?
> > > >
> > > > I am suspecting that the cache is not entirely cleared, because when
> I
> > > try
> > > > to do a search on the same query as I did before the search, it still
> > > has a
> > > > return QTime that is much faster than the initial search. However,
> > when I
> > > > do a search on a new query, the return QTime is the original speed.
> > > >
> > > > I am using Solr 5.4.0, and this is my setting for the
> queryResultCache.
> > > >
> > > >  > > >  size="1024"
> > > >  initialSize="512"
> > > >  autowarmCount="0"/>
> > >
> > > The Solr caches are maintained in the Java heap, which is lost when
> Java
> > > stops.
> > >
> > > Although the Solr caches are not preserved across a restart, the
> > > operating system does cache actual index data in main memory, so when
> > > Solr asks for the same index data off of the disk again, it is pulled
> > > directly from RAM, which is a LOT faster than the disk.  In order to
> > > deliver good performance, Solr is extremely reliant on this built-in
> > > feature of all modern operating systems, so there must be enough spare
> > > memory for good caching.
> > >
> > > Here are a couple of pages with some more detail:
> > >
> > > https://wiki.apache.org/solr/SolrPerformanceProblems
> > > https://en.wikipedia.org/wiki/Page_cache
> > >
> > > Thanks,
> > > Shawn
> > >
> > >
> >
>
>
>
> --
> --
>
> Benedetti Alessandro
> Visiting card : http://about.me/alessandro_benedetti
>
> "Tyger, tyger burning bright
> In the forests of the night,
> What immortal hand or eye
> Could frame thy fearful symmetry?"
>
> William Blake - Songs of Experience -1794 England
>

Re: Is Solr cache cleared when I restart Solr?

[Alessandro Benedetti]

As already specified you need to distinguish between Solr Cache and OS
Memory mapped files.
What you should clearly notice in your situation is an increase of space
for the OS Memory mapped files.
Which means faster access to index segments ( almost all the different data
structures are memory mapped ).

Related the internal Solr Cache, if you haven't changed the java memory
properties, I would expect not that much difference.
If you were on a virtual machine sharing physical memory with other virtual
instances, you could find benefits on the other hand.

Cheers


On 28 January 2016 at 05:44, Zheng Lin Edwin Yeo 
wrote:

> Thanks Erick and Shawn for your reply.
>
> We have recently upgraded the server RAM from 64MB to 192MB, and I noticed
> that this caching occurs after we upgraded the RAM. Previously, the cache
> may not even be preserved in the same Solr session.
> So is it true that the upgrading of the server RAM creates enough spare
> memory for good caching?
>
> Regards,
> Edwin
>
>
> On 28 January 2016 at 12:27, Shawn Heisey  wrote:
>
> > On 1/27/2016 8:11 PM, Zheng Lin Edwin Yeo wrote:
> > > I would like to find out, is the cache in the Solr cleared when I shut
> > down
> > > the Solr instant and restart it?
> > >
> > > I am suspecting that the cache is not entirely cleared, because when I
> > try
> > > to do a search on the same query as I did before the search, it still
> > has a
> > > return QTime that is much faster than the initial search. However,
> when I
> > > do a search on a new query, the return QTime is the original speed.
> > >
> > > I am using Solr 5.4.0, and this is my setting for the queryResultCache.
> > >
> > >  > >  size="1024"
> > >  initialSize="512"
> > >  autowarmCount="0"/>
> >
> > The Solr caches are maintained in the Java heap, which is lost when Java
> > stops.
> >
> > Although the Solr caches are not preserved across a restart, the
> > operating system does cache actual index data in main memory, so when
> > Solr asks for the same index data off of the disk again, it is pulled
> > directly from RAM, which is a LOT faster than the disk.  In order to
> > deliver good performance, Solr is extremely reliant on this built-in
> > feature of all modern operating systems, so there must be enough spare
> > memory for good caching.
> >
> > Here are a couple of pages with some more detail:
> >
> > https://wiki.apache.org/solr/SolrPerformanceProblems
> > https://en.wikipedia.org/wiki/Page_cache
> >
> > Thanks,
> > Shawn
> >
> >
>



-- 
--

Benedetti Alessandro
Visiting card : http://about.me/alessandro_benedetti

"Tyger, tyger burning bright
In the forests of the night,
What immortal hand or eye
Could frame thy fearful symmetry?"

William Blake - Songs of Experience -1794 England

Re: Is Solr cache cleared when I restart Solr?

[Shawn Heisey]

On 1/27/2016 8:11 PM, Zheng Lin Edwin Yeo wrote:
> I would like to find out, is the cache in the Solr cleared when I shut down
> the Solr instant and restart it?
>
> I am suspecting that the cache is not entirely cleared, because when I try
> to do a search on the same query as I did before the search, it still has a
> return QTime that is much faster than the initial search. However, when I
> do a search on a new query, the return QTime is the original speed.
>
> I am using Solr 5.4.0, and this is my setting for the queryResultCache.
>
>   size="1024"
>  initialSize="512"
>  autowarmCount="0"/>

The Solr caches are maintained in the Java heap, which is lost when Java
stops.

Although the Solr caches are not preserved across a restart, the
operating system does cache actual index data in main memory, so when
Solr asks for the same index data off of the disk again, it is pulled
directly from RAM, which is a LOT faster than the disk.  In order to
deliver good performance, Solr is extremely reliant on this built-in
feature of all modern operating systems, so there must be enough spare
memory for good caching.

Here are a couple of pages with some more detail:

https://wiki.apache.org/solr/SolrPerformanceProblems
https://en.wikipedia.org/wiki/Page_cache

Thanks,
Shawn

Re: Is Solr cache cleared when I restart Solr?

[Erick Erickson]

Caches are in-memory structures, there's no provision in Solr
to try to preserve them across a shutdown, they'd have to be written
to disk then re-read.

Any intermediate cached pages, i.e. something in you app server is
another story however. Solr has no control over that.

Best,
Erick

On Wed, Jan 27, 2016 at 7:11 PM, Zheng Lin Edwin Yeo
 wrote:
> Hi,
>
> I would like to find out, is the cache in the Solr cleared when I shut down
> the Solr instant and restart it?
>
> I am suspecting that the cache is not entirely cleared, because when I try
> to do a search on the same query as I did before the search, it still has a
> return QTime that is much faster than the initial search. However, when I
> do a search on a new query, the return QTime is the original speed.
>
> I am using Solr 5.4.0, and this is my setting for the queryResultCache.
>
>   size="1024"
>  initialSize="512"
>  autowarmCount="0"/>
>
> Regards,
> Edwin

Is Solr cache cleared when I restart Solr?

[Zheng Lin Edwin Yeo]

Hi,

I would like to find out, is the cache in the Solr cleared when I shut down
the Solr instant and restart it?

I am suspecting that the cache is not entirely cleared, because when I try
to do a search on the same query as I did before the search, it still has a
return QTime that is much faster than the initial search. However, when I
do a search on a new query, the return QTime is the original speed.

I am using Solr 5.4.0, and this is my setting for the queryResultCache.



Regards,
Edwin

Re: Is Solr cache cleared when I restart Solr?

[Zheng Lin Edwin Yeo]

Thanks Erick and Shawn for your reply.

We have recently upgraded the server RAM from 64MB to 192MB, and I noticed
that this caching occurs after we upgraded the RAM. Previously, the cache
may not even be preserved in the same Solr session.
So is it true that the upgrading of the server RAM creates enough spare
memory for good caching?

Regards,
Edwin


On 28 January 2016 at 12:27, Shawn Heisey  wrote:

> On 1/27/2016 8:11 PM, Zheng Lin Edwin Yeo wrote:
> > I would like to find out, is the cache in the Solr cleared when I shut
> down
> > the Solr instant and restart it?
> >
> > I am suspecting that the cache is not entirely cleared, because when I
> try
> > to do a search on the same query as I did before the search, it still
> has a
> > return QTime that is much faster than the initial search. However, when I
> > do a search on a new query, the return QTime is the original speed.
> >
> > I am using Solr 5.4.0, and this is my setting for the queryResultCache.
> >
> >  >  size="1024"
> >  initialSize="512"
> >  autowarmCount="0"/>
>
> The Solr caches are maintained in the Java heap, which is lost when Java
> stops.
>
> Although the Solr caches are not preserved across a restart, the
> operating system does cache actual index data in main memory, so when
> Solr asks for the same index data off of the disk again, it is pulled
> directly from RAM, which is a LOT faster than the disk.  In order to
> deliver good performance, Solr is extremely reliant on this built-in
> feature of all modern operating systems, so there must be enough spare
> memory for good caching.
>
> Here are a couple of pages with some more detail:
>
> https://wiki.apache.org/solr/SolrPerformanceProblems
> https://en.wikipedia.org/wiki/Page_cache
>
> Thanks,
> Shawn
>
>