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From "Vijay (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-3623) use MMapedBuffer in CompressedSegmentedFile.getSegment
Date Fri, 23 Dec 2011 22:42:32 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-3623?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13175606#comment-13175606
] 

Vijay commented on CASSANDRA-3623:
----------------------------------

I did it Again, i confused everyone with my test data :)
Hot methods shown above is the only data which is from the trunk rest are without CRC (hot
methods without CRC and without this patch is as follows).


Excl. User CPU   Name

  sec.      %
629.460 100.00   <Total>
336.913  53.52   <static>@0x54999 (<snappy-1.0.4.1-libsnappyjava.so>)
50.074   7.96   org.apache.cassandra.io.compress.CompressedRandomAccessReader.<init>(java.lang.String,
org.apache.cassandra.io.compress.CompressionMetadata, boolean)
43.057   6.84   org.apache.cassandra.io.util.RandomAccessReader.<init>(java.io.File,
int, boolean)
35.623   5.66   memcpy
33.555   5.33   <static>@0xd8e9 (<libpthread-2.5.so>)
30.673   4.87   Copy::pd_disjoint_words(HeapWord*, HeapWord*, unsigned long)
26.384   4.19   CompactibleFreeListSpace::block_size(const HeapWord*) const
15.199   2.41   SpinPause
11.966   1.90   BlockOffsetArrayNonContigSpace::block_start_unsafe(const void*) const
 8.479   1.35   CardTableModRefBSForCTRS::card_will_be_scanned(signed char)
 8.007   1.27   CardTableModRefBS::non_clean_card_iterate_work(MemRegion, MemRegionClosure*,
bool)
 5.169   0.82   madvise
 5.059   0.80   ParallelTaskTerminator::offer_termination(TerminatorTerminator*)
 4.146   0.66   CardTableModRefBS::process_chunk_boundaries(Space*, DirtyCardToOopClosure*,
MemRegion, MemRegion, signed char**, unsigned long, unsigned long)
 2.431   0.39   CardTableModRefBS::dirty_card_range_after_reset(MemRegion, bool, int)
 1.375   0.22   SweepClosure::do_blk_careful(HeapWord*)
 0.825   0.13   Par_PushOrMarkClosure::do_oop(oopDesc*)
 0.616   0.10   GenericTaskQueue<oopDesc*, 131072>::pop_local(oopDesc*&)
 0.561   0.09   instanceKlass::oop_oop_iterate_nv(oopDesc*, Par_PushOrMarkClosure*)
 0.473   0.08   CardTableModRefBS::process_stride(Space*, MemRegion, int, int, DirtyCardToOopClosure*,
MemRegionClosure*, bool, signed char**, unsigned long, unsigned long)
 0.374   0.06   Par_MarkFromRootsClosure::scan_oops_in_oop(HeapWord*)
 0.319   0.05   BitMap::par_at_put(unsigned long, bool)
 0.308   0.05   MemRegion::intersection(MemRegion) const
 0.275   0.04   munmap
 0.220   0.03   CardTableModRefBS::dirty_card_iterate(MemRegion, MemRegionClosure*)


Hope this makes sense.
                
> use MMapedBuffer in CompressedSegmentedFile.getSegment
> ------------------------------------------------------
>
>                 Key: CASSANDRA-3623
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-3623
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Core
>    Affects Versions: 1.1
>            Reporter: Vijay
>            Assignee: Vijay
>              Labels: compression
>             Fix For: 1.1
>
>         Attachments: 0001-MMaped-Compression-segmented-file-v2.patch, 0001-MMaped-Compression-segmented-file.patch,
0002-tests-for-MMaped-Compression-segmented-file-v2.patch
>
>
> CompressedSegmentedFile.getSegment seem to open a new file and doesnt seem to use the
MMap and hence a higher CPU on the nodes and higher latencies on reads. 
> This ticket is to implement the TODO mentioned in CompressedRandomAccessReader
> // TODO refactor this to separate concept of "buffer to avoid lots of read() syscalls"
and "compression buffer"
> but i think a separate class for the Buffer will be better.

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