Step 3 - Enable large page use in WebSphere Application Server

To allow the WebSphere Application Server process to utilize the available large page size, set the LDR_CNTRL environment variable from within the console.

Open the WebSphere integrated solutions console.

In the navigation tree, expand Servers, click Application servers, and select the appropriate server.

Expand Java and Process Management and click Process Definition.

Click Environment Entries, then click New.

Set LDR_CNTRL to the value LARGE_PAGE_DATA=Y. Refer to Figure 6-4 to see an example.

Figure 6-4 Setting LDR_CNTRL in the Process Definition

 

 

Step 4 - Verify actual large page usage

You can use the vmstat command to see page size usage statistics. To see statistics displayed on a per-page basis, enter the vmstat -P all command. See Example 6-8 for sample output that includes 16 MB large pages in use. The actual pages used appear in column avm. In the example, twenty-one 16 MB pages are in use.

Example 6-8 View page size statistics per page 

# vmstat -P all


System configuration: mem=8192MB


pgsz            memory                           page

----- -------------------------- ------------------------------------

           siz      avm      fre    re    pi    po    fr     sr    cy

   4K   561424   382048   130451     0     0     0     0      0     0

  64K    30447     2093    28354     0     0     0     0      0     0

  16M      256       21      233     0     0     0     0      0     0

An alternative way to view the actual page usage, but on a per-process basis, is to use the -Z option. Example 6-8 shows that a data page size of 16 MB is being used for the server process, which in this case has a PID of 364600.

Example 6-9 View page size statistics per process 

# ps -Z -p 364600

    PID    TTY  TIME DPGSZ SPGSZ TPGSZ CMD

 364600  pts/1  0:58   16M    4K    4K java