I am interested on these parameters to improve jackrabbit performance. I
have an installation with more than 2 million of documents and performance
is actually poor :(
On the current trunk there are 3 parameters which can be used to tweak
performance for jcr2spi/spi2davex. These are the size of the item info
cache, the size of the item cache and the depth of batch read operations.
Some Background:
The item cache contains JCR items (i.e. nodes and properties). The item
info cache contains item infos. An item info is an entity representing
nodes or properties on the SPI layer. The jcr2spi module receives item
infos from an SPI implementation (i.e. spi2davex) and uses them to build
up a hierarchy of JCR items.
When an item is requested from the JCR API, jcr2spi first checks whether
the item is in the item cache. If so, that item is returned. If not, the
request is passed down to the SPI. But before actually calling the SPI
the item info cache is check first. If this cache contains the requested
item info the relevant part of the JCR hierarchy is build and the
corresponding JCR item is placed into the item cache. Only when the item
info cache does not contain the requested item info a call will be made
to the SPI. Here the batch read depth comes into play. Since calls to
the SPI cause some latency (i.e. network round trips), the SPI may - in
addition to the actually requested item info - return additional item
infos. The batch read depth parameter specifies the depth down to which
item infos of the children of the requested item info are returned.
Overall the size of the item info cache and the batch read depth should
be used to optimize for the requirements of the back-end (i.e. network
and server). In general, the item info cache should be large enough to
*easily* hold all items from multiple batches. The batch read depth
should be a trade off between network latency and item info cache
overhead. Finally the item cache should be used to optimize for the
requirements of the front-end (i.e. the JCR API client). It should be
able to hold the items in the current working set of the API consumer.
Some pointers:
Batch reading: org.apache.jackrabbit.spi.RepositoryService#getItemInfos()
org.apache.jackrabbit.spi2davex.Spi2davexRepositoryServiceFactory#PARAM_BATCHREAD_CONFIG
Item info cache size:
org.apache.jackrabbit.spi2davex.Spi2davexRepositoryServiceFactory#PARAM_ITEMINFO_CACHE_SIZE
Item cache size:
org.apache.jackrabbit.jcr2spi.Jcr2spiRepositoryFactory#PARAM_ITEM_CACHE_SIZE
Related JIRA issues:
JCR-2497: Improve jcr2spi read performance
JCR-2498: Implement caching mechanism for ItemInfo batches
JCR-2461: Item retrieval inefficient after refresh
JCR-2499: Add simple benchmarking tools for jcr2spi read perform
Michael
On 2/28/10 9:21 PM, Paco Avila wrote:
El 28/02/2010 15:50, "Michael Dürig"<[email protected]> escribió:
François,
I spent some time on improving performance lately. See
https://issues.apache.org/jira/browse/JCR-2497 and related issues.
I was able to improve performance for our use case with these fixes. Getting
the parameters right (i.e. item cache size, item info cache size and batch
read depth) is still quite tricky though and requires careful profiling.
I can provide more specific information on these parameters if required.
Michael
François Cassistat wrote:
Ok, I've studied a little what was going on with a packet analyze...
