Christopher Currens created LUCENENET-495:
---------------------------------------------
Summary: Use of DateTime.Now causes huge amount of
System.Globalization.DaylightTime object allocations
Key: LUCENENET-495
URL: https://issues.apache.org/jira/browse/LUCENENET-495
Project: Lucene.Net
Issue Type: Bug
Components: Lucene.Net Core
Affects Versions: Lucene.Net 2.9.4, Lucene.Net 3.0.3
Reporter: Christopher Currens
Assignee: Christopher Currens
Priority: Critical
Fix For: Lucene.Net 3.0.3
This issue mostly just affects RAMDirectory. However, RAMFile and
RAMOutputStream are used in other (all?) directory implementations, including
FSDirectory types.
In RAMOutputStream, the file last modified property for the RAMFile is updated
when the stream is flushed. It's calculated using {{DateTime.Now.Ticks /
TimeSpan.TicksPerMillisecond}}. I've read before that Microsoft has regretted
making DateTime.Now a property instead of a method, and after seeing what it's
doing, I'm starting to understand why. DateTime.Now is returning local time.
In order for it to calculate that, it has to get the utf offset for the
machine, which requires the creation of a _class_,
System.Globalization.DaylightTime. This is bad for performance.
Using code to write 10,000 small documents to an index (4kb sizes), it created
1,570,157 of these DaylightTime classes, a total of 62MB of extra
memory...clearly RAMOutputStream.Flush() is called a lot.
A fix I'd like to propose is to change the RAMFile from storing the
LastModified date to UTC instead of local. DateTime.UtcNow doesn't create any
additional objects and is very fast. For this small benchmark, the performance
increase is 31%.
I've set it to convert to local-time, when {{RAMDirectory.LastModified(string
name)}} is called to make sure it has the same behavior (tests fail otherwise).
Are there any other side-effects to making this change?
--
This message is automatically generated by JIRA.
If you think it was sent incorrectly, please contact your JIRA administrators:
https://issues.apache.org/jira/secure/ContactAdministrators!default.jspa
For more information on JIRA, see: http://www.atlassian.com/software/jira
