1. Installing GemStone/S 64 Bit Version 3.2.6

1. Shared memory

The upper limit for shared memory single segment size and total usage should be set to values larger than your desired Shared Page Cache size, and not more than 75% of your real memory size.

The single segment maximum size, shmmax, is set in bytes, and the total shared memory limit, shmall, is configured in pages, with a base page size of 4KB. Note that the results of ipcs may be reported in kbytes.

For example, if you have 8192 MB of real memory:

8192 MB * .75 = 6144 MB

6144 MB * 220 = 6442450944 bytes

6442450944 / 4K = 1572864

To set shared memory sizes, you would append the following text to the /etc/sysctl.conf file. The settings are read from this file during the boot process.

# Shared Memory setting for GemStone

kernel.shmall = 1572864

kernel.shmmax = 6442450944

For more details, consult your Linux operating system documentation.

2. Semaphores

You may need to increase the settings for semaphores. semmsl sets the maximum number of semaphores per id (per semaphore set). This parameter limits the number of GemStone sessions that can log in to a particular Stone and connect to its shared page cache. (Note that semmsl ends with a lowercase L, not a digit.)

On the Stone’s node, this parameter must provide two semaphores for each user who will log in to that Stone from any node plus an overhead of four. In distributed systems, nodes that have only user sessions must provide two semaphore for each user session on that node plus an overhead of one.

The number of semaphores actually requested for a particular shared page cache depends on the GemStone configuration file read by the process that starts the cache and is (SHR_PAGE_CACHE_NUM_PROCS * 2) + 1.

semmns sets the total number of semaphores in the system. This parameter limits the total number of GemStone sessions on a node. Keep this setting >= semmsl (above).

3. File Descriptors

A file descriptor limit of 1024 is adequate for up to about 500 GemStone users. Each user session requires two file descriptors, and others are needed for extents, transaction logs, and overhead. Consequently, you may need to set the nfile parameter to a larger value, such as 2048. Use caution and increase the default setting only when necessary because doing so can have system side effects.

4. Locking the Shared Page Cache in memory

If you intend to lock the shared page cache into memory via the stone configuration option SHR_PAGE_CACHE_LOCKED, then the linux user starting the stone must either have the Linux capability CAP_IPC_LOCK, or have a RLIMIT_MEMLOCK resource limit set greater than the size of the SPC.

5. OOM Killer

If your system runs low on memory, the Linux OOM killer may select GemStone processes to terminate. To protect the shared page cache and other critical GemStone processes, each GemStone process’s oom_score_adj, which is used to select processes to terminate, is adjusted. If the userid that will be running the server processes has the CAP_SYS_RESOURCE privilege, critical GemStone processes have their oom_score_adj reduced, making them safer; if the user does not have CAP_SYS_RESOURCE, then non-critical processes such as Gems have their score increased, so they will be selected rather than more critical processes.

To set CAP_SYS_RESOURCE on kernels v2.6.32 and later, set the capability on the executables:

a. Install 'libcap2-bin'

b. for i in pgsvrmain gem stoned shrpcmonitor; do sudo setcap cap_sys_resource=pe $GEMSTONE/sys/$i ; done

c. for i in startstone topaz; do sudo setcap cap_sys_resource=pe $GEMSTONE/bin/$i ; done

6. PAM

If you are using UNIX authentication for GemStone logins, or if you run NetLDI as root with setuid (i.e. not in guest mode), you must have PAM (Pluggable Authentication Module) configured on the server. You may include a specific GemStone authorization service name, or allow the default “other” authentication definitions to be used.

PAM authentication definitions are files under the directory /etc/pam.conf/.

The specific GemStone service file names are gemstone.gem for user authentication, and gemstone.netldi for a NetLDI running with authentication.

The libraries that are specified in the stack depend on how you are configuring PAM to perform the authentication. The examples below are for PAM configured to invoke LDAP for authentication.

For example, to allow GemStone UNIX authentication, which uses PAM, to authenticate via LDAP, create a file named /etc/pamd.conf/gemstone.gem with the following contents:

auth	required	pam_ldap.so

For NetLDI authentication, again using LDAP, create a file named /etc/pamd.conf/gemstone.netldi with the following contents:

auth	required	pam_ldap.so

Red Hat, by default, installs a file /etc/pamd.conf/other which disables “other” authentication. On Ubuntu, it is enabled by default. You can allow the “other” authentication stack to be used for GemStone authentication by ensuring that the file /etc/pamd.conf/other has the following contents:

auth	required	pam_ldap.so

Consult your System Administrators for more information on how authentication is handled on your system.

7. Large Memory Pages

The default size for memory pages is 4KB. If you have a large repository, using large pages may improve performance. To use large pages (2MB), you must configure Linux to allocate large pages, and configure GemStone to use large pages.

To configure the use of Large Pages:

a. Determine the number of large pages to configure, based on your GemStone configuration.

Start the shared page cache monitor shell

unix> $GEMSTONE/sys/shrpcmonitor

Enter the intended shared page cache size, maximum number of GemStone processes, and the number of shared counters, using the commands setcachesizekb, setnumprocs, setnumsharedctrs, with postfix notation.

This example is for an (approximately) 20GB shared page cache, 200 processes, and 1900 shared counters:

SHRPCMON>20000000 setcachesizekb

SHRPCMON>200 setnumprocs

SHRPCMON>1900 setnumsharedctrs

b. Use the getrequiredsize command to compute the large page requirements.

SHRPCMON>getrequiredsize

For 1250000 pages, 200 processes and 1900 shared counters,

required cache size is 21942435840 bytes.

To use 2 MB large memory pages: 21942501376 bytes are

required for alignment.

Number of 2 MB large pages required: 10463

c. configure Linux to use large pages using the following commands, which are also output by get requiredsize. You must execute these as root.

To enable large pages until the next system reboot:

echo numpages > /proc/sys/vm/nr_hugepages

To permanently enable large pages:

echo "vm.nr_hugepages=numpages" >> /etc/sysctl.conf

You can confirm large memory pages are available for use with:

grep Huge /proc/meminfo

d. Configure the executables to use large pages:

/sbin/setcap cap_ipc_lock=pe $GEMSTONE/sys/startshrpcmon

/sbin/setcap cap_ipc_lock=pe $GEMSTONE/sys/shrpcmonitor

Alternatively, the SPC monitor process can be run with an effective user ID of root:

chown root $GEMSTONE/sys/shrpcmonitor $GEMSTONE/sys/startshrpcmon

chmod u+s $GEMSTONE/sys/shrpcmonitor $GEMSTONE/sys/startshrpcmon

e. Configure GemStone to request large pages by set the configuration option SHR_PAGE_CACHE_LARGE_MEMORY_PAGE_POLICY = 2

8. Configuring GemStone’ Shared Page Cache

The configuration option SHR_PAGE_CACHE_SIZE_KB defines the size (in KBytes) of extent page space in the shared page cache. The maximum acceptable value for this configuration option is limited by system memory, kernel configurations, cache space allocated by SHR_PAGE_CACHE_NUM_PROCS and space allocated for other GemStone caches.

For more general information about these and other configuration options, see Appendix A of the System Administration Guide.

9. System clock

The system clock must be set to the correct time. When GemStone opens the repository at startup, it compares the current system time with the recorded checkpoint times as part of a consistency check. A system time earlier than the time at which the last checkpoint was written may be taken as an indication of corrupted data and prevent GemStone from starting. The time comparisons use GMT.

10. TCP keepalive option

GemStone processes ordinarily use the TCP keepalive option to determine how long they will wait after communications activity ceases unexpectedly. This setting can be useful for reaping stale RPC Gems, but the operating system default may not be appropriate for this purpose. For further information, refer to your operating system documentation.

Do you want the installation script to set up directories for server lock files and NetLDI logs?

The default location for server lock files and NetLDI log files is /opt/gemstone, although for compatibility with earlier products /usr/gemstone is used only if it exists. If the environment variable GEMSTONE_GLOBAL_DIR is defined to point to a valid directory, this overrides the default server lock files and log file location; however, all Gemstone processes that will interact on this machine must have this environment variable set to the same directory.

If these directories do not exist, the installation script offers to create /opt/gemstone and the subdirectories locks and log. Then, the script offers to set access (770) to these directories.

If you answer no to creating the directories, you must create them (or provide a symbolic link) before starting the server.

Do you want the installation script to set the owner and group for all the files in the GemStone distribution?

If you answer yes, the script will prompt you for the owner and group you want to use. Refer to Chapter 1 of the System Administration Guide for more information about setting owner and group permissions.

If you answer no, the permissions will remain the same as when the files were extracted from the distribution media.

Do you want the installation script to protect the repository file?

The default, which we recommend, gives only the owner read and write access (600) through ordinary UNIX commands. Other users can read and write the repository through a GemStone session. If you choose not to protect the repository, the setuid bit is cleared from all executables, which causes them to run under ownership of the user who invokes them.

Default: Set the repository permission to 600, and leave the setuid bit applied.

Allow NetLDI to Run as Root?

Do you want the installation script to allow non-root users to start a NetLDI that runs as root?

The NetLDI is a network server that permits remote processes to interact with the repository. There are two ways to set up a NetLDI so that it can provide services to all GemStone users: it can run as root, or it can run in guest mode with a captive account.

• To run NetLDIs as root, accept the default “yes” response. Ownership of the NetLDI executable is changed to root, and the setuid bit is set. Any GemStone user will be able to start a NetLDI process that is accessible to all GemStone users because it will always run as root. For certain services, users will need to authenticate themselves by supplying a password. Alternatively, answer “no” but log in as root before starting the NetLDI.

If the NetLDI uses a port number less than 1024, it must run as root.

• To run NetLDIs in guest mode with a captive account, answer “no” to the prompt, because those modes are not permitted if the NetLDI runs as root. “Guest mode” means that GemStone users do not have to supply a UNIX password to use NetLDI services. The “captive account” is an account that owns all processes the NetLDI starts; typically, it is the GemStone administrative account that owns the files. You must start the NetLDI while logged in as that account.

Default: Change ownership of the netldi executable to root, and set its setuid bit.

Set up an Extent?

Do you want the installation script to set up an extent now?

GemStone is distributed with a read-only copy of the initial repository in
$GEMSTONE/bin/extent0.dbf. Before you can start GemStone, this file must be copied to a suitable location and made writable. The script offers to copy the file to its default location of $GEMSTONE/data.

If you are a new GemStone user, we recommend that you answer y. If you are an existing GemStone user, you might prefer to answer n, then copy the extent to a different location yourself. (If you choose a location other than the default, you must edit your configuration file before starting GemStone. For information, see the System Administration Guide.)

Default: Place a writable copy of extent0.dbf in $GEMSTONE/data.

Start a NetLDI?

Do you want the installation script to start a NetLDI?

If you prefer, you can start these processes manually at any time.

Almost every host needs a NetLDI. You must start a NetLDI when the Stone repository monitor or Gem session processes will run on this machine.

You can start a NetLDI that runs as root by answering yes to this prompt and the confirmation that follows. However, if you want to start the NetLDI in guest mode with a captive account, you must do that after completing the installation. For more information about guest mode with captive account, see Chapter 3 of the System Administration Guide.

Default: Do not start a NetLDI at this time.

Start an Object Server?

As root, you cannot start an object server, but the script offers to start one as another user. You will start the server later in the installation, so answer no.

Default: Do not start an object server at this time.

Log out as root

Log out as user root. The rest of the installation is done as the GemStone administrative user.