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https://issues.apache.org/jira/browse/HBASE-13082?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15033596#comment-15033596
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ramkrishna.s.vasudevan commented on HBASE-13082:
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bq.sortCompactedfiles This is already been called on new temp ArrayList. Do we
still need create a new list? May be to be best way is create ImmutableList
here at end for setting to instance variable
Stack suggested not to use Guava DS and APIs.
bq.Can the marking be done within addCompactionResults?
If we do this way then we have to add the markcompactedAway in all the
compaction impl. This way it will be better. Also better we do it inside the
store level lock.
bq.That looks bad this API checks the status of compactedAway also.
The name is Ok I think. Any other name you suggest?
bq.isCompactedAway() {
This is used in tests only because wanted to check some conditions for the
tests.
bq.Better add similar API in StoreFile also and use that rather than using
directly from reader.
This cannot be done so easily because all our StorefileScanners are created
over the Reader. So if we want to access from Storefile then it will be a
bigger change. Any way there is a follow up that was discussed to make things
work with StoreFileManager and StorefileInfo getting used by the manager.
bq.removeCompactedFiles -> Every time the chore runs, we seems to make a
ThreadPoolExecutor and ExecutorService which seems expensive. Why we need multi
threaded reader close?
The close() is a costly operation hence did not want to do these things
serially when we know that we can do it parallely. The reason for creating the
executor every time was that not sure what is the thread count to be allocated
to the executor.
bq.Should be ok as it is rare case also.. Just saying.
YA if there are very frequent flushes then this will happen, till then the GC
will not be cleared for that snapshot till the scan is over.
bq.HRegion region; -> Do we need this ref of HRegion type? Can be Region?
Okie that can be done I think.
> Coarsen StoreScanner locks to RegionScanner
> -------------------------------------------
>
> Key: HBASE-13082
> URL: https://issues.apache.org/jira/browse/HBASE-13082
> Project: HBase
> Issue Type: Bug
> Reporter: Lars Hofhansl
> Assignee: ramkrishna.s.vasudevan
> Attachments: 13082-test.txt, 13082-v2.txt, 13082-v3.txt,
> 13082-v4.txt, 13082.txt, 13082.txt, HBASE-13082.pdf, HBASE-13082_1.pdf,
> HBASE-13082_12.patch, HBASE-13082_13.patch, HBASE-13082_14.patch,
> HBASE-13082_15.patch, HBASE-13082_16.patch, HBASE-13082_17.patch,
> HBASE-13082_1_WIP.patch, HBASE-13082_2.pdf, HBASE-13082_2_WIP.patch,
> HBASE-13082_3.patch, HBASE-13082_4.patch, HBASE-13082_9.patch,
> HBASE-13082_9.patch, HBASE-13082_withoutpatch.jpg, HBASE-13082_withpatch.jpg,
> LockVsSynchronized.java, gc.png, gc.png, gc.png, hits.png, next.png, next.png
>
>
> Continuing where HBASE-10015 left of.
> We can avoid locking (and memory fencing) inside StoreScanner by deferring to
> the lock already held by the RegionScanner.
> In tests this shows quite a scan improvement and reduced CPU (the fences make
> the cores wait for memory fetches).
> There are some drawbacks too:
> * All calls to RegionScanner need to be remain synchronized
> * Implementors of coprocessors need to be diligent in following the locking
> contract. For example Phoenix does not lock RegionScanner.nextRaw() and
> required in the documentation (not picking on Phoenix, this one is my fault
> as I told them it's OK)
> * possible starving of flushes and compaction with heavy read load.
> RegionScanner operations would keep getting the locks and the
> flushes/compactions would not be able finalize the set of files.
> I'll have a patch soon.
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