Is there multiple process or single process with multiple threads ?
- The Enteprise server operates in either a
multi-process/multi-threaded or single process/multi-threaded mode.
Multi-process has some performance and reliability advantages on
certain OSes. NT version does not support multi-process mode. In the
multi-process case, the processes are spawned when the server is
started and individual processes are respawned should they die.
How are threads spawned by the server ?
- Threads are created in each process in groups of approximately
RqThrottleMinThreadsPerSocket (default is 50) as needed. Threads are
reused to avoid the overhead of creating and destroying them.
All platforms, except Solaris, attempt to keep
RqThrottleMinThreadsPerSocket in accept at any given time. On
Solaris, better performance (and to avoid an OS limitation for
2.5.1) are attained if Solaris is limited to a few as 1 thread at a
time in accept. For Solaris 2.6 multi-processor systems, it is best
to limit the accept threads to 1 per processor and the server should
be configured to achieve this.
Does Enterprise killed process after n requests ?
- Enterprise server does not killed a process unless a shutdown is
requested. Note this true for ES 3.x.
What is the Native Threads Pool ?
- ES 3.x server uses an abstractions portability layer that
provides access to the host O/S services like threads. Therefore
this layer provides threads that are not always the same as the O/S
native threads. These non-native threads have lower scheduling
overhead so to improves performance. However, these threads are
sensitive to blocking calls such as I/O ones. For NSAPI extensions
which uses blocking calls, the server keeps a pool of threads which
safely support blocking calls. Usually these threads are native OS
threads.
During request processing any NSAPI function which is not marked as
being safe for execution on a non-native thread is scheduled for
execution on one of the native threads pool. If you have written
your own NSAPI plug-ins such as NameTrans, Service, or PathCheck
functions, these will execute on a thread pool thread by default. If
your extension makes use of the NSAPI functions for I/O exclusively,
or none at all, then it should be fine for it to execute on a
non-native thread. To achieve this the function must be loaded with
a NativeThread=no. For existing code, add the option NativeThread="no"
to the "load-modules" Init line in obj.conf like this:
Init funcs="pcheck_uri_clean_fixed_init" shlib="C:/Netscape/p186244/P186244.dll"
fn="load-modules" NativeThread="no". The flag
affects all functions in the funcs list, so if you have more than
one function in a library but only some of them should get the flag
use two Init lines.
Are NSAPI functions executing in the Native Thread Pool ?
- NSAPI functions are not required to execute on the thread pool,
only functions that perform blocking I/O calls are required to
execute in the pool. Most internal functions do not fall into this
category and so execute on the original thread servicing the
request. To be safe, functions execute there by default.
How do I set the number of native threads ?
- The maximum number of native threads that may be in the thread
pool which is determined by the setting of the NSCP_POOL_THREADMAX
environment variable. This should be set as low as possible to
sustain the optimal volume of requests. If you are not saturating
your CPU but are seeing requests queue up then you should increase
this number.
On NT, CGI requests execute on a native thread so for smaller NT
servers a lower number may actually improve throughput
substantially. This is because large numbers of processes are not
particularly efficient under NT. A suggested value when CGIs are
your primary application load would be ~12/cpu
Can global data structures be shared by threads ?
- The data structure must be available as a global symbol for all
threads to be able to see it. If all of your request threads must
have access to the same data one must deal with care with
contention lock which can limit performance.
Server starts multiple process but my NSAPI init function is only
called once ?
- That is the case if the init function is called in the
magnus.conf, not recommended since ES 2.x, or a LateInit="no"
option is set (see
this tech note). With LateInit="yes" init functions
are executed after the process fork
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