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large-pages variable set but mysql doesn't use huge pages
Posted by: Andres March
Date: February 14, 2008 06:36PM

I hope that this is something I'm simply doing wrong. Running on RHEL4. I have enabled 2GB of Huge Pages and set the large-pages variable but MySQL is not using them. I'm currently loading a large db (> 20GB). Here is some stats:

bash-3.00# cat /proc/meminfo
MemTotal: 7914912 kB
MemFree: 23612 kB
Buffers: 356 kB
Cached: 11800 kB
SwapCached: 4095316 kB
Active: 5758588 kB
Inactive: 12764 kB
HighTotal: 0 kB
HighFree: 0 kB
LowTotal: 7914912 kB
LowFree: 23612 kB
SwapTotal: 16779884 kB
SwapFree: 11352936 kB
Dirty: 0 kB
Writeback: 0 kB
Mapped: 5761552 kB
Slab: 27532 kB
CommitLimit: 19713340 kB
Committed_AS: 8264048 kB
PageTables: 17916 kB
VmallocTotal: 536870911 kB
VmallocUsed: 8956 kB
VmallocChunk: 536861555 kB
HugePages_Total: 1000
HugePages_Free: 1000
Hugepagesize: 2048 kB

Notice no Huge Pages are being used. Now checking the db:

mysql> show variables like '%large%';
+---------------------+---------+
| Variable_name | Value |
+---------------------+---------+
| large_files_support | ON |
| large_page_size | 2097152 |
| large_pages | ON |
+---------------------+---------+
3 rows in set (0.19 sec)

So this doesn't make sense. I also made sure the limits were wide open for the process to grab memory:

bash-3.00# cat /etc/security/limits.conf

mysql soft memlock unlimited
mysql hard memlock unlimited

What am I doing wrong? Check out what the process is using:

Mem: 7914912k total, 7873636k used, 41276k free, 2448k buffers
Swap: 16779884k total, 5516492k used, 11263392k free, 56944k cached

PID USER PR NI %CPU TIME+ %MEM VIRT RES SHR S COMMAND
19364 mysql 16 0 25 145:00.93 70.2 8042m 5.3g 2632 S mysqld

HELP!

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