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https://issues.apache.org/jira/browse/SOLR-4589?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13606933#comment-13606933
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Hoss Man commented on SOLR-4589:
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bq. The easiest fix would be to make realValue volatile (and readers will thus
cross a read memory barrier).
I don't fully understand what situation you are concerned about here, but
making it volatile is easy .. running tests now.
bq. Does this happen with Solr?
no, but the way the public API for LazyDocument is defined, it is possible
(even though it wouldn't really make any sense given the way the API is really
only usable from a StoredFieldVisitor) so i wanted to protect against it -- i
included test randomization to verify that the edge case works.
> 4.x + enableLazyFieldLoading + large multivalued fields + varying fl =
> pathological CPU load & response time
> ------------------------------------------------------------------------------------------------------------
>
> Key: SOLR-4589
> URL: https://issues.apache.org/jira/browse/SOLR-4589
> Project: Solr
> Issue Type: Bug
> Affects Versions: 4.0, 4.1, 4.2
> Reporter: Hoss Man
> Assignee: Hoss Man
> Fix For: 4.3, 5.0, 4.2.1
>
> Attachments: SOLR-4589.patch, SOLR-4589.patch, SOLR-4589.patch,
> test-just-queries.out__4.0.0_mmap_lazy_using36index.txt,
> test-just-queries.sh, test.out__3.6.1_mmap_lazy.txt,
> test.out__3.6.1_mmap_nolazy.txt, test.out__3.6.1_nio_lazy.txt,
> test.out__3.6.1_nio_nolazy.txt, test.out__4.0.0_mmap_lazy.txt,
> test.out__4.0.0_mmap_nolazy.txt, test.out__4.0.0_nio_lazy.txt,
> test.out__4.0.0_nio_nolazy.txt, test.out__4.2.0_mmap_lazy.txt,
> test.out__4.2.0_mmap_nolazy.txt, test.out__4.2.0_nio_lazy.txt,
> test.out__4.2.0_nio_nolazy.txt, test.sh
>
>
> Following up on a [user report of exterme CPU usage in
> 4.1|http://mail-archives.apache.org/mod_mbox/lucene-solr-user/201302.mbox/%[email protected]%3E],
> I've discovered that the following combination of factors can result in
> extreme CPU usage and excessively HTTP response times...
> * Solr 4.x (tested 3.6.1, 4.0.0, and 4.2.0)
> * enableLazyFieldLoading == true (included in example solrconfig.xml)
> * documents with a large number of values in multivalued fields (eg: tested
> ~10-15K values)
> * multiple requests returning the same doc with different "fl" lists
> I haven't dug into the route cause yet, but the essential observations is: if
> lazyloading is used in 4.x, then once a document has been fetched with an
> initial fl list X, subsequent requests for that document using a differnet fl
> list Y can be many orders of magnitute slower (while pegging the CPU) -- even
> if those same requests using fl Y uncached (or w/o lazy laoding) would be
> extremely fast.
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