JavaScript: OS detection
Operating System
Question: Can I use JavaScript to detect the operating system on the client machine?
To detect the operating system on the client machine,
your script can analyze the value of navigator.appVersion or navigator.userAgent.
Below is a simple example of a script that sets the variable OSName
to reflect the actual client OS.
// This script sets OSName variable as follows:
// "Windows"
for all versions of Windows
// "MacOS"
for all versions of Macintosh OS
// "Linux"
for all versions of Linux
for all other UNIX flavors
// "Unknown OS" indicates failure to detect the OS
var OSName="Unknown OS";
if (navigator.appVersion.indexOf("Win")!=-1) OSName="Windows";
if (navigator.appVersion.indexOf("Mac")!=-1) OSName="MacOS";
if (navigator.appVersion.indexOf("X11")!=-1) OSName="UNIX";
if (navigator.appVersion.indexOf("Linux")!=-1) OSName="Linux";
document.write('Your OS: '+OSName);
On your system, this script yields the following result:
(To get more detailed OS information, your script should perform
a more sophisticated analysis of navigator.appVersion or navigator.userAgent,
but the idea would be the same.)
Some clients may spoof their navigator.userAgent string,
i.e. substitute another OS name (or any string at all) for the user agent value.
Generally, your code should not rely on navigator.userAgent to do anything important.
© , .Sun Java System Application Server Standard and Enterprise Edition 7 2004Q2 Performance and Tuning Guide 
Tuning the Operating System
Tuning Solaris TCP/IP settings benefits programs that open and close many sockets. The Application Server operates with a small fixed set of connections and the performance gain may not be as significant on the Application Server node. Improvements for the Web Server, configured as a Web front-end to Application Server, can have significant benefits. The following topics are discussed:
The following table shows operating system tuning, for Solaris, used when benchmarking for performance and scalability. These values are an example of how you may tune your system to achieve the desired result.
Table 5-1  Tuning the Solaris Operating System
rlim_fd_max
/etc/system
Process open fi should account for the expected load (for the associated sockets, files, pipes if any).
rlim_fd_cur
/etc/system
sq_max_size
/etc/system
Controls strea setting to 0 makes it infinity so the performance runs wont be hit by lack of buffer space. Set on clients too.
tcp_close_wait_interval
ndd /dev/tcp
Set on clients as well.
tcp_time_wait_interval
ndd /dev/tcp
tcp_conn_req_max_q
ndd /dev/tcp
tcp_conn_req_max_q0
ndd /dev/tcp
tcp_ip_abort_interval
ndd /dev/tcp
tcp_keepalive_interval
ndd /dev/tcp
For high traffic web sites lower this value.
tcp_rexmit_interval_initial
ndd /dev/tcp
If retransmission is greater than 30-40%, you should increase this value.
tcp_rexmit_interval_max
ndd /dev/tcp
tcp_rexmit_interval_min
ndd /dev/tcp
tcp_smallest_anon_port
ndd /dev/tcp
Set on clients too.
tcp_slow_start_initial
ndd /dev/tcp
Slightly faster transmission of small amounts of data.
tcp_xmit_hiwat
ndd /dev/tcp
To increase the transmit buffer.
tcp_recv_hiwat
ndd /dev/tcp
To increase the transmit buffer.
tcp_recv_hiwat
ndd /dev/tcp
To increase the receive buffer.
tcp_conn_hash_size
ndd /dev/tcp
The connection hash table keeps all the information for active TCP connections (ndd -get /dev/tcp tcp_conn_hash). This value does not limit the number of connections, but it can cause connection hashing to take longer. To make lookups more efficient, set the value to half of the number of concurrent TCP connections that you expect on the server (netstat -nP tcp|wc -l, gives you a number). It defaults to 512. This can only be set in /etc/system and becomes effective at boot time.
On Solaris, setting the maximum number of open files property using ulimit has the biggest impact on your efforts to support the maximum number of RMI/IIOP clients.
To increase the hard limit, add the following command to /etc/system and reboot it once:
set rlim_fd_max = 8192
You can verify this hard limit by using the following command:
ulimit -a -H
Once the above hard limit is set, you can increase the value of this property explicitly (up to this limit) using the following command:
ulimit -n 8192
You can verify this limit by using the following command:
For example, with the default ulimit of 64, a simple test driver can support only 25 concurrent clients, but with ulimit set to 8192, the same test driver can support 120 concurrent clients. The test driver spawned multiple threads, each of which performed a JNDI lookup and repeatedly called the same business method with a think (delay) time of 500ms between business method calls, exchanging data of about 100KB.
These settings apply to RMI/IIOP clients (on Solaris). Refer to Solaris documentation on the Sun Microsystems documentation web site (www.) for more information on setting the file descriptor limits.
For further information on solaris system tunables, please refer to the Solaris Tunable Parameters reference manual located at .
The following are some options that need to be considered when tuning solaris on x86 platform for the application server and HADB. Please note that some of the values will depend on the system resources available.
The following should be added to the /etc/system. These affect the number of semaphores and also the shared memory settings. These are more releavant for the machine on which HADB server is running.
These settings affect the shared memory and semaphores on the system:
set shmsys:shminfo_shmmax=0xffffffff
set shmsys:shminfo_shmseg=128
set semsys:seminfo_semmnu=1024
set semsys:seminfo_semmap=128
set semsys:seminfo_semmni=400
set semsys:seminfo_semmns=1024
These settings are for the file descriptors:
set rlim_fd_max=65536
set rlim_fd_cur=65536
set sq_max_size=0
set tcp:tcp_conn_hash_size=8192
set autoup=60
set pcisch:pci_stream_buf_enable=0
These settings are for tuning the IP stack:
set ip:tcp_squeue_wput=1
set ip:tcp_squeue_close=1
set ip:ip_squeue_bind=1
set ip:ip_squeue_worker_wait=10
set ip:ip_squeue_profile=0
Place the following changes to the default tcp variables in a startup script that gets executed when the system reboots, or else you will lose your changes:
ndd -set /dev/tcp tcp_time_wait_interval 60000
ndd -set /dev/tcp tcp_conn_req_max_q 16384
ndd -set /dev/tcp tcp_conn_req_max_q0 16384
ndd -set /dev/tcp tcp_ip_abort_interval 60000
ndd -set /dev/tcp tcp_keepalive_interval 7200000
ndd -set /dev/tcp tcp_rexmit_interval_initial 4000
ndd -set /dev/tcp tcp_rexmit_interval_min 3000
ndd -set /dev/tcp tcp_rexmit_interval_max 10000
ndd -set /dev/tcp tcp_smallest_anon_port 32768
ndd -set /dev/tcp tcp_slow_start_initial 2
ndd -set /dev/tcp tcp_xmit_hiwat 32768
ndd -set /dev/tcp tcp_recv_hiwat 32768
Note:After making any changes to the /etc/system, you need to reboot the machines.
To tune for maximum performance on Linux, you’ll:
Having more number of file desc. ensures that the server can open the sockets under highload and thus not abort requests coming in from the clients.
Start by checking system limits for file descriptors with this command:
% cat /proc/sys/fs/file-max
The current limit shown is 8192. To increase it to 65535 (as root):
# echo &65535& & /proc/sys/fs/file-max
If you want this new value to survive across reboots you can add it to /etc/sysctl.conf o specify the maximum number of open files permited:
fs.file-max = 65535
Note: The parameter is not proc.sys.fs.file-max, as one might expect.
To list the available parameters that can be modified using sysctl:
% sysctl -a
To load new values from the sysctl.conf file:
% sysctl -p /etc/sysctl.conf
To check and modify limits per shell:
8192 kbytes
coredumpsize
descriptors
memorylocked
The openfiles and descriptors show a limit of 1024. To increase the limit to 65535 for all users, edit /etc/security/limits.conf as root, and modify or add the &nofile& (number of file) entries:
*     soft
nofile           65535
*     hard
nofile           65535
(Here “*” is a wildcard that identifies all users. You could also specify a userid, instead.)
Then edit /etc/pam.d/login and add the line:
/lib/security/pam_limits.so
Note:On RedHat, you also need to edit /etc/pam.d/sshd and add the line,session required /lib/security/pam_limits.so
On many systems, this procedure will be sufficient. Log in as a regular user and try it before doing the remai steps. (They may not be required, depending on how PAM and ssh are configured.)
Add the following to
/etc/rc.local
15 4 2 & /proc/sys/vm/bdflush
For more information view the manpages for bdflush.
For HADB settings please refer to .
Add the following entry into /etc/rc.local
mii-tool -F 100baseTx-FD eth0, where eth0 is the name of the NIC.
For non scsi disks:
Test the speed using
/sbin/hdparm -t /dev/hdX
Enable DMA:
/sbin/hdparm -d1 /dev/hdX
Check the speed again using the hdparm command.1
Given that DMA wasn't enabled by default, the transfer rate should now have improved considerably. In order to do this at every reboot, add the /sbin/hdparm -d1 /dev/hdX line to your /etc/conf.d/local.start, /etc/init.d/rc.local, or whatever you call your startup script.
For SCSI Disks: Please refer to the following URL: /alikins/system_tuning.html#scsi
Add the following entry below into the /etc/rc.local
echo 30 & /proc/sys/net/ipv4/tcp_fin_timeout
echo 60000 & /proc/sys/net/ipv4/tcp_keepalive_time
echo 15000 & /proc/sys/net/ipv4/tcp_keepalive_intvl
echo 0 & /proc/sys/net/ipv4/tcp_window_scaling
And add the following to /etc/sysctl.conf
# Disables packet forwarding
net.ipv4.ip_forward = 0
# Enables source route verification
net.ipv4.conf.default.rp_filter = 1
# Disables the magic-sysrq key
kernel.sysrq = 0
net.ipv4.ip_local_port_range =
net.core.rmem_max = 262140
net.core.rmem_default = 262140
net.ipv4.tcp_rmem =
net.ipv4.tcp_wmem =
net.ipv4.tcp_sack = 0
net.ipv4.tcp_timestamps = 0
net.ipv4.tcp_window_scaling = 0
net.ipv4.tcp_keepalive_time = 60000
net.ipv4.tcp_keepalive_intvl = 15000
net.ipv4.tcp_fin_timeout = 30
Then, add the following as the last entry in /etc/rc.local
sysctl -p /etc/sysctl.conf
Note:After making these changes, you need to reboot the system.
Finally, use this command to increase the size of the transmit buffer:
tcp_recv_hiwat ndd /dev/tcp