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https://issues.apache.org/jira/browse/TRAFODION-2478?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15864249#comment-15864249
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ASF GitHub Bot commented on TRAFODION-2478:
-------------------------------------------
Github user selvaganesang commented on a diff in the pull request:
https://github.com/apache/incubator-trafodion/pull/953#discussion_r100873849
--- Diff: core/sql/cli/memorymonitor.cpp ---
@@ -223,12 +229,12 @@ void MemoryMonitor::update(float &scale) {
char * currPtr;
bytesRead = fread(buffer, 1, 2048, fd_meminfo_);
// Make sure there wasn't an error (next fseek will clear eof)
- if (!feof(fd_meminfo_))// Make sure there wasn't an error
- {
- scale = 6;
- pressure_ = 0;
- return;
- }
+ if (ferror(fd_meminfo_))
+ assert(false);
+ if (feof(fd_meminfo_))
+ clearerr(fd_meminfo_);
+ else
+ buffer[bytesRead] = '\0';
--- End diff --
fread cpp reference says the following:
Number of objects read successfully, which may be less than count if an
error or end-of-file condition occurs.
It looks like feof is treated like an error condition.
This code assumed that buffer is always big enough. I can change it to get
rid of this assumption
> Reduce the number of memory monitoring threads in Trafodion SQL processes
> ---------------------------------------------------------------------------
>
> Key: TRAFODION-2478
> URL: https://issues.apache.org/jira/browse/TRAFODION-2478
> Project: Apache Trafodion
> Issue Type: Improvement
> Components: sql-exe
> Affects Versions: any
> Reporter: Selvaganesan Govindarajan
> Assignee: Selvaganesan Govindarajan
>
> A memory monitor thread is created in every SQL process to handle the memory
> pressure in BMO (Big memory operators). This has following drawbacks:
> 1) No consistent view of the memory pressure in the node
> 2) Overhead of calculating the memory pressure in every trafodion SQL process.
> Proposal is to move this thread to RMS SSCP process. All SQL processes have
> access to RMS shared segment. Hence SQL processes can get the view of the
> memory pressure readily and easily from the shared segment.
> It is also possible to increase the frequency of the memory pressure
> calculation to get near real tiime picture of the memory pressure.
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