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https://issues.apache.org/jira/browse/HBASE-21874?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16773962#comment-16773962
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Wellington Chevreuil commented on HBASE-21874:
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Thanks for the detailed explanations, [~ram_krish] and [~anoop.hbase]!
For the record, while testing latest patch that removed the configurable buffer
size, got a "Map failed" OOME on java.nio.FileChannelImpl, while trying to map
a 490GB pmem device. This is due linux default max number of map handlers
defined by *max_map_count* being currently 64K. With a fixed buffer size of
4MB, that will limit the pmem capacity to 256GB, so we need to expand that
limit, for example, to use a 500GB pmem device, at least 128k handlers are
needed:
{noformat}
sysctl -w vm.max_map_count=130000
{noformat}
> Bucket cache on Persistent memory
> ---------------------------------
>
> Key: HBASE-21874
> URL: https://issues.apache.org/jira/browse/HBASE-21874
> Project: HBase
> Issue Type: New Feature
> Components: BucketCache
> Affects Versions: 3.0.0
> Reporter: ramkrishna.s.vasudevan
> Assignee: ramkrishna.s.vasudevan
> Priority: Major
> Fix For: 3.0.0
>
> Attachments: HBASE-21874.patch, HBASE-21874.patch,
> HBASE-21874_V2.patch, Pmem_BC.png
>
>
> Non volatile persistent memory devices are byte addressable like DRAM (for
> eg. Intel DCPMM). Bucket cache implementation can take advantage of this new
> memory type and can make use of the existing offheap data structures to serve
> data directly from this memory area without having to bring the data to
> onheap.
> The patch is a new IOEngine implementation that works with the persistent
> memory.
> Note : Here we don't make use of the persistence nature of the device and
> just make use of the big memory it provides.
> Performance numbers to follow.
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