56-5.6.36-rel82.0.el6.x86_64 OOM

Hi,

I am experiencing the following issue on

56-5.6.36-rel82.0.el6.x86_64

In a period of about 6 minutes the amount of memory in the Linux page cache drops from about 12GB to 0GB. When this occurs the Out of Memory Killer kills the mysqld process.

Oddly, the amount of memory being used by MySQL is steady during this period (I am using the PMM graph "MySQL Internal Memory Overview" to determine this). No MySQL related charts show any odd behavior during the time period leading up to the OOM.

User CPU time does increase during the period leading up to the OOM.

I ran perf record a few times during one of the periods where user CPU time was increasing and the page cache was dropping right before the OOM. What I consistently saw was:

"my_lfind" using about 15% CPU time
"buf_flush_dirty_pages" using about 7% CPU time.

Is anyone familiar enough with these functions to provide some clues as to what may be going on here?

thanks