[
https://issues.apache.org/jira/browse/DRILL-5122?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Paul Rogers updated DRILL-5122:
-------------------------------
Assignee: (was: Paul Rogers)
> DrillBuf performs very expensive logging if JVM -ea option is set
> -----------------------------------------------------------------
>
> Key: DRILL-5122
> URL: https://issues.apache.org/jira/browse/DRILL-5122
> Project: Apache Drill
> Issue Type: Improvement
> Components: Server
> Affects Versions: 1.8.0
> Reporter: Paul Rogers
> Priority: Minor
>
> The {{DrillBuf}} class is the foundation of Drill's direct memory model. It
> has a very sophisticated allocator mechanism behind it. {{DrillBuf}} provides
> logging to help track down memory leaks and other issues. Unfortunately, the
> trigger to turn on this option is based on detecting if assertions are
> enabled in the JVM.
> Assertions are very handy tools: they are debug-only assertions not executed
> at run time. They are turned on with the "-ea" option to the JVM. But, in
> production, the assertions don't execute, avoiding production-time costs.
> In Drill, once assertions are enabled, the dominant cost of a query becomes
> {{DrillBuf}} logging. One example showed that {{DrillBuf}} logging increases
> query cost by 10x.
> Debugging of {{DrillBuf}} is handy for those few engineers who need to do so.
> Over time, {{DrillBuf}} has become quite stable so that, now, most
> developers, most of the time, do not work on {{DrillBuf}}.
> One wonders: Drill uses Guava preconditions extensively. Is this perhaps due
> to the high cost of enabling assertions? Since assertions were unavailable,
> production-time checking via Guava may have become preferred. Assertions are,
> in fact, better because they incur no overhead in production, while Guava
> preconditions always execute, even in production. (Here we assume that the
> code errors that both check will find errors during development so that such
> errors do not sneak through into production.)
> The code does have a way to turn off debugging, but only if a system property
> is set on every run. Since Drill has hundreds of unit tests that people might
> run, this requires creating custom run configurations for each.
> This enhancement proposes to modify {{DrillBuf}} to enable logging only when
> a) assertions are enabled (so we know it is a debug environment) and b) when
> a boot-time configuration property is set (so that logging can be turned off
> for most developers most of the time.) Optionally, b) can be a system
> property that _enables_ (not disables) {{DrillBuf}} logging.
> The code in question:
> {code}
> class BaseAllocator ... {
> public static final boolean DEBUG = AssertionUtil.isAssertionsEnabled()
> || Boolean.parseBoolean(System.getProperty(DEBUG_ALLOCATOR, "false"));
> ...
> class DrillBuf ... {
> public boolean release(int decrement) {
> ...
> if (BaseAllocator.DEBUG) {
> historicalLog.recordEvent("release(%d). original value: %d", decrement,
> refCnt + decrement);
> }
> {code}
--
This message was sent by Atlassian JIRA
(v6.3.4#6332)
