There is still the broader question - as the overall memory of a node
(NC) has to be shared among the three kinds of memory (at least) that I
also mentioned just a minute ago:
- buffer cache (global/shared memory for caching pages of disk
components)
- in-memory components (i.e., the current thread's topic)
- working memory (needed for hash-based and sort-based operators like
joins/aggs)
Whatever we do next should probably start keeping in mind this
bigger-picture/zero-sum game.
On 3/10/16 3:23 PM, Jianfeng Jia wrote:
Another way is to allocate the entire global space upfront, but there is no
upper-bound for each dataset. The bigger dataset gets more pages. The drawback
is that we may waste more space if all dataset are all small.
The ideal case is there is only one dynamically memory allocation manager with
one global upper-bound, and all datasets can share the space without an extra
bound per dataset.
On Mar 10, 2016, at 2:55 PM, Yingyi Bu <[email protected]> wrote:
A more fundament question Is it possible that all those datasets share a
global budget in a multi-tenant way?
In principle, the budget should just be a upper-bound. If a dataset doesn't
need that much, it shouldn't pre-allocate all
"storage.memorycomponent.numpages"
pages.
However, in the current implementation, we pre-allocate all in-memory pages
upfront:
https://github.com/apache/incubator-asterixdb-hyracks/blob/master/hyracks/hyracks-storage-am-lsm-common/src/main/java/org/apache/hyracks/storage/am/lsm/common/impls/VirtualBufferCache.java#L247
I think we should fix it to dynamically allocate memory when needed. (Disk
buffer cache already does that.)
Best,
Yingyi
On Thu, Mar 10, 2016 at 2:46 PM, Jianfeng Jia <[email protected]>
wrote:
Dear Devs,
I have some questions about the memory management of the in-memory
components for different datasets.
The current AsterixDB backing the cloudberry demo is down every few days.
It always throws an exception like following:
Caused by: org.apache.hyracks.api.exceptions.HyracksDataException: Failed
to open index with resource ID 7 since it does not exist.
As described in ASTERIXDB-1337, each dataset has a fixed budget no matter
how small/big it is. Then the number of datasets can be loaded at the same
time is also fixed by $number =
storage.memorycomponent.globalbudget/storage.memorycomponent.numpages. My
question is if we have more than $number of datasets, then the eviction
will happen? Will it evict a entire dataset of the victim? Base on the
symptom of above exception, it seems the metadata get evicted? Could we
protect the metadata from eviction?
A more fundament question Is it possible that all those datasets share a
global budget in a multi-tenant way?
In my workload there are one main dataset( ~10Gb) and five tiny auxiliary
datasets (each size <20M). In addition, the client will create a bunch of
temporary datasets depends on how many concurrent users are and each
temp-dataset will be “refreshed" for a new query. (The refresh is done by
drop and create the temp-dataset). It’s hard to find one
storage.memorycomponent.numpages that make every dataset happy.
Best,
Jianfeng Jia
PhD Candidate of Computer Science
University of California, Irvine
Best,
Jianfeng Jia
PhD Candidate of Computer Science
University of California, Irvine
