Quantcast
Channel: SCN : All Content - SAP IQ
Viewing all articles
Browse latest Browse all 716

SA CR 728597 / Linux Kernel direct i/o bug & huge pages

$
0
0

Last year, April -> October, I asked the question about IQ supporting Huge Pages on Linux.  It was mentioned that under SA CR 728597 and Red Hat Bug 891857 that there was a bug in the Linux kernel handling of direct I/O while using transparent huge memory pages (a variant of Linux Huge memory pages). 

 

CR 728597:

This problem is related to a possible bug in the transparent huge pages (THP) feature introduced in these operating system versions.  Red Hat bug 891857 has been created to track this issue.

 

The problem can be triggered by calling an external environment, xp_cmdshell, or other procedure that causes a fork while other I/O is occurring.  A known limitation with the Linux kernel limits the use of fork while doing O_DIRECT I/O operations.  Essentially what can happen is that the data can come from or go to the wrong process’ memory after the fork.  SQL Anywhere performs O_DIRECT I/O operations according to the documented safe usage.  However, THP appears to cause further problems and the O_DIRECT I/O data comprising database page reads/writes appears to get lost.

 

http://scn.sap.com/thread/3338917 and http://froebe.net/blog/2013/06/17/does-anyone-have-any-details-on-redhat-linux-bug-891857/

 

Does anyone know the status of this ongoing FIVE year old issue?

 

jason


Viewing all articles
Browse latest Browse all 716

Trending Articles



<script src="https://jsc.adskeeper.com/r/s/rssing.com.1596347.js" async> </script>