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When a system is running slowly and performance is degrading
it is difficult to know what is the cause. Whether it is lack
of memory or a particular application, there are ways to diagnose
the situation. This article provides performance monitoring tips,
some concepts like Intimate Shared Memory (ISM) and priority paging,
web sites for further reading, and some diagnostic suggestions,
like how to read vmstat output. The emphasis is on Solaris 2.6
and Solaris 7.
CONTENTS
I. PERFORMANCE MONITORING
A. SE Toolkit
B. Sun Performance Information
C. Looking for a Performance Bottleneck?
1. Using the vmstat Command
2. About Free Memory
3. Sample Quick Performance Script
II. TOPICS ON KERNEL PARAMETERS AND TUNING THE SOLARIS KERNEL
A. Adrian Cockcroft's Perspective on Tuning
B. Understanding 64-bit Sizing and Capacities
1. Definitions and Concepts
2. Performance
3. Sample Commands
C. Commonly Asked About Kernel Parameters
1. KAIO and MAXASYNCHIO
2. About File Descriptors and Their Limitations
2a. Using select() library function
3. Adjusting Pseudo-terminal Devices (ptys)
D. Performance and Database Tuning
1. Priority Paging
2. Intimate Shared Memory (ISM)
2a. ISM Defaults
2b. Swap Configurations Related to Shared Memory
3. Interprocess Communication Parameters (IPC)
3a. Shared Memory Parameters
3b. Semaphore Parameters
3c. Message Queue Parameters
III. APPENDIX
A. Sample Quick Performance Script
IV. REFERENCES
A. IPC articles in SunSolve SRDBs and InfoDoc Collections
B. More SunWorld Online Articles
C. New Book on Oracle8 and Unix Performance Tuning
D. What Are The Kernel Patch Numbers?
==========================
I. PERFORMANCE MONITORING
A. SE Toolkit
There are commercial products for performance monitoring
but the best is the SE Toolkit, produced by Sun engineers
and available using the following URL:
http://www.sun.com/sun-on-net/performance/se3/
It reports disk activity, cpu usage, TCP and network connections,
memory and more. It is easy to install, does not require a reboot,
and displays graphically that is easy understand.
B. Sun Performance Information
The Sun Performance Information page is available using this URL:
http://www.sun.com/sun-on-net/performance.html
It has links to articles written by Adrian Cockcroft, including all
of his SunWorld Online Q&A Columns, and the SE Toolkit. Adrian Cockcroft
co-authored Sun's authoritative book on performance and tuning:
"Sun Performance and Tuning - Java and the Internet"
It is also available at the above URL. There are new chapters
in the Second Edition (199 including the last 2 chapters dedicated
entirely to the SE Toolkit and its performance rules.
C. Looking for a Performance Bottleneck?
When a system is not performing to expectations, it is necessary
to determine where the bottleneck is. Entire system hangs and process
hangs are beyond the scope of this article. In the case of what appears
to be an entire system hang, kernel core files may need to be generated.
First call your Sun Solution Center to develop a course of action.
When looking for a performance bottleneck, review and monitor the following
as the initial step for diagnosing a problem:
/etc/system - review configuration parameters and what has
been recently changed
/var/adm/messages - look for WARNINGS, errors, reboots, panics etc
prtconf - contains system information including
amount of RAM
prtdiag - check for errors and hardware failures
swap -l - review swap configuration
/etc/release - contains operating system release information
pkginfo -l - provides a complete listing of packages installed
and their release and version numbers
showrev -p - a listing of patches installed
To see the top processes using CPU and memory:
ps -eo pid,pcpu,args | sort +1n %cpu
ps -eo pid,vsz,args | sort +1n kilobytes of virtual memory
/usr/ucb/ps aux |more output is sorted with highest
users (processes) of cpu and
memory at the top
1. Using the vmstat Command
---------------------------
The command vmstat is more concise and provides more information per
line than the sar command. Here we can see a classic example of not
enough cpu capacity for the executing applications.
% vmstat 15
procs memory page disk faults cpu
r b w swap free re mf pi po fr de sr m0 m1 m2 m3 in sy cs us sy id
45 0 0 2887216 182104 3 707 449 6 455 0 80 2 6 1 0 1531 5797 983 61 30 9
58 0 0 2831312 46408 5 983 582 56 3211 0 492 0 0 0 0 1413 4797 1027 69 31 0
55 0 0 2830944 56064 2 649 656 3 806 0 121 0 0 0 0 1441 4627 989 69 31 0
57 0 0 2827704 48760 4 818 723 6 800 0 121 0 0 1 0 1606 4316 1160 66 34 0
56 0 0 2824712 47512 6 857 604 56 1736 0 261 0 0 1 0 1584 4939 1086 68 32 0
58 0 0 2813400 47056 7 856 673 33 2374 0 355 0 0 0 0 1676 5112 1114 70 30 0
60 1 0 2816712 49464 7 861 720 6 731 0 110 7 0 3 0 2329 6131 1067 64 36 0
58 0 0 2817552 48392 4 585 521 0 996 0 146 0 0 0 0 1357 6724 1059 71 29 0
56 0 0 2821256 52616 3 675 435 1 148 0 24 0 0 0 0 1554 5914 1150 68 32 0
^ ^
| |
The column labeled "r" under the procs section is the run queue of
processes waiting to get on the cpus. The "id" column is cpu idle
time. This machine lacks the cpu resources to keep up with the process
demand. If adding cpus does not help this condition then a review of
application code would be needed. As it turned out in this case, upgrading
from an Ultra2 to an Ultra 4500 fixed the problem and the applications
are running fine.
2. About Free Memory
--------------------
To look for a shortage of memory, do not rely upon the "free" column.
That column is not an indication of a lack of memory. Much has
been written on this subject in the SunWorld articles and "Sun Performance
and Tuning". To determine if there is a lack of memory examine at
the 12th column, "sr", or scan rate.
If that column sustains high numbers (hundreds to thousands of pages/second),
then there is not enough memory for the processes or files wanting to be
loaded
into memory, and adding more memory is likely to help. By default,
lotsfree is 1/64 of memory. That is why the free column usually hovers
just above 1/64 of physical memory (RAM).
The pageout scanner runs only when the free list shrinks below a threshold
(lotsfree in pages). Any process or file inactive and not locked in memory
will be paged out. The size of the freelist will appear to shrink to a very
small value (determined by the tunable parameter "lotsfree" , and will remain
at that value. The page daemon will "kick in" and look for more memory to
reclaim from exited and idle processes when the amount on the freelist drops
below the lotsfree threshold. There is no way for the "free" value to
grow much above the threshold, because there is no way to get the page
daemon to work to reclaim memory beyond the threshold. lotsfree can be
increased but then memory is wasted.
What all of this means, is that the size of the freelist is no indication of
how much free memory there really is, because there may be a great amount of
unused memory which has yet to be reclaimed by the page daemon, because the
page daemon has no need to reclaim it.
Files are also mapped directly into memory by processes using the mmap
command.
This command maps in the code and shared libraries for a process. Pages may
have multiple references from several processes while also being resident
in the filesystem cache. A recent optimization is that pages with eight or
more
references are skipped by the scanner, even if they are inactive. This feature
helps shared libraries and multiprocess server code stay resident in memory.
(p. 332 " erformance & Tuning - Java and the Internet"
See also:
The Memory-Go-Round - Confused by "free memory?"
http://www.sunworld.com/swol-05-1997/swol-05-perf.html
Clearing up swap space confusion - Why don't swap space numbers add up?
http://www.sunworld.com/swol-07-1998/swol-07-perf.html
3. Sample Quick Performance Script
----------------------------------
It is important to get a "snapshot" of the system when
trying to determine a performance bottleneck. The
"Sample Quick Performance Script" (see Appendix) uses
the netstat, mpstat, vmstat, iostat, and ps commands to
monitor system activity. Just running one of these command
does not provide the context necessary for a complete
debugging of the problem.
This script doesn't need to be run by cron, it stops execution
at 200 iterations (while [ $X != 200 ]), and it is easily modifiable.
It does not contain crash(1M) kmastat and map kernelmap output
which is included in other scripts available in the SRDBs/InfoDoc
SunSolve collections, primarily because kernel memory leaks are rare.
However, crash is useful for determining kernel memory fragmentation.
See Appendix A for the Sample Quick Performance Script
=============================================================
II. TOPICS ON KERNEL PARAMETERS AND TUNING THE SOLARIS KERNEL
A. Adrian Cockcroft's Perspective
To start our discussion of whether to tune the Solaris
kernel, here are important points to keep in mind from
Adrian Cockcroft, author of SE Toolkit (see I. A. above):
Tuning the kernel is a hard subject to deal with. Some
tunables are well known and easy to explain. Others
are more complex or change from one release to the
next. The settings in use are often based on out-of-date
folklore. (page 349 - "Sun Performance and Tuning -
Java and the Internet"
So why is there so much emphasis on kernel tuning?
And why are there such high expectations of the
performance boost available from kernel tweaks? I
think the reasons are historical, and I'll return
to my car analogy to explain it. (page 351 - "Sun
Performance and Tuning - Java and the Internet"
The author goes on to talk about the difference between 1970s
cars that had, for example, carburetors that needed to be rebuilt
and workshop manuals for car repair, with the cars of
today. Now in the 1990's, computerized ignition and fuel injection
really makes self repair a thing of the past as there just aren't
user serviceable engine components.
Continuing on page 351:
Unix started out in an environment where the end users
had source code and did their own tuning and support. If you like
this way of working, you probably already run the free
Unix clone, Linux, on your PC at home. As Unix became a
commercial platform for running applications, the end users
changed. Commercial users just want to run their application,
and tinkering with the operating system is a distraction.
SunSoft engineers have put a lot of effort into automating
the tuning for Solaris 2. It adaptively scales according to
the hardware capabilities and the workload it is running.
... The self-configuring and tuning nature of Solaris
contributes to its ease of use and greatly reduces the
gains from tweaking it yourself. Each successive version
of Solaris 2 has removed tuning variables by converting
hand-adjusted values into adaptively managed limits.
If SunSoft can describe a tunable variable and when it should be
tuned in detail, they could either document this in the
manual or implement the tuning automatically. In most
cases, automatic tuning has been implemented. The tuning
manual should really tell you which things don't need to be
tuned any more, but it doesn't. This is one of my complaints
about the manual, which is really in need of a complete
rewrite. It is too closely based on the original Unix
System V manual from many years ago when things did need tuning.
page 351 - "Sun Performance and Tuning - Java and the Internet"
B. Understanding 64-bit Sizing and Capacities
1. Definitions and Concepts
---------------------------
What is meant by 64 bits and what are the performance gains?
Here's what 64 bits means and how it is used:
1) 64-bit arithmetic operations -
Most computer languages support 64-bit arithmetic options.
Full-speed, 64-bit, floating-point and integer arithmetic has been
available since the SuperSPARC shipped in 1992. A full set of
64-bit floating-point registers and accelerations are available
in V8plus mode on UltraSPARC and further accelerations are
available in SPARC V9. (See p. 136 and 137 "erformance and Tuning
- Java and the Internet"
2) 64-bit data types -
The size of the int and long data types have been agreed on
by the Unix industry. The agreement is to leave int as 32 bits
but to make long 64 bits. Prepare your code in advance by
using long to perform pointer arithmetic. This approach
is known as the LP64 option. (See p. 137 "erformance and Tuning
- Java and the Internet"
3) 64-bit internal and external buses -
A good description of CPU datapaths and external interfaces
and caches can be found on page 138 of "erformance and Tuning
- Java and the Internet". SuperSPARC and UltraSPARC (and earlier)
are at least 64 bits wide and the fastest designs are wider still.
4) 64-bit addressing -
This is the latest developement in the history and evolution
of 64 bit capability. Pointers and addresses (process address space
and memory address space) go from 32-bit quantities to 64-bit
quantities. 64-bit addressing capability refers to the size of
the linear address space that can be manipulated directly by the CPU
and with 64-bit addressing it is greater than 4 Gbytes.
The 64-bit solaris 7 kernel needs 64-bit device drivers.
Previous device drivers will only work in a 32-bit kernel.
64-bit applications can only use 64-bit libraries.
A 64-bit application cannot link with a 32-bit library.
2. Performance
--------------
To summarize how performance is affected by 64 bit addressing,
here is an excerpt from the SunWorld article titled "What's new
in Solaris 7?"
From a performance point of view, the ability to run 64-bit
applications on Solaris 7 has two main benefits. One is that
much larger problems can be solved efficiently using a
bigger process address space; the other is that integer
arithmetic computations get to use 64-bit registers and operations.
Overall, programs get slightly larger due to larger pointer
values in code and data structures. This in turn means that
CPU caches are a little less likely to have enough cache lines,
and a slight slowdown might occur in programs that
could run just as well in a 32-bit environment.
For the complete article visit the URL:
http://www.sunworld.com/swol-11-1998/swol-11-perf.html
3. Sample Commands
------------------
To determine the running kernel and supported instruction
set on Solaris 7 see man page for the isainfo command.
For example:
% isainfo -v
64-bit sparcv9 applications
32-bit sparc applications
The file command can be used to identify binaries or libraries:
For example:
% file /kernel/drv/sparcv9/poll
/kernel/drv/sparcv9/poll:ELF 64-bit MSB relocatable
SPARCV9 Version 1
% file /kernel/drv/poll
/kernel/drv/poll:ELF 32-bit MSB relocatable SPARC Version 1
In addition, see the man page on largefile(5):
% man largefile
NAME
largefile - large file status of utilities
DESCRIPTION
On a 32-bit system, a large file is a regular file whose
size is greater than or equal to 2 Gbyte (2**31 bytes). A
small file is a regular file whose size is less than 2
Gbyte.
...
For more information see "orting Performance Tools to 64bit Solaris
White Paper" (URL http://www.sun.com/sun-on-net/performance.html)
C. Commonly Asked About Kernel Parameters
1. KAIO and MAXASYNCHIO
-----------------------
One kernel parameter that can not be adjusted is the kernel
async I/O parameter, (also known as KAIO, or MAXASYNCHIO).
Starting with Solaris 2.4 the kernel provides direct support for KAIO.
The Solaris 2.5.1 implementation of KAIO is the first to permit
operation on full 64-bit devices. Previous versions supported
device sizes of only 2 GB or less.
2. About File Descriptors and Their Limitations
-----------------------------------------------
Processes may need to open many files or sockets as file
descriptors. Standard I/O (stdio) library functions have
a defined limit of 256 file descriptors as the fopen() call,
datatype char, will fail if it can not get a file descriptor between
0 and 255. The open() system call is of datatype
int, removing this limitation. However, if open() has opened
0 to 255 file descriptors without closing any, fopen() will
not be able to open any file descriptors as all the low-numbered
ones have been used up. Applications that need to use many
file descriptors to open a large number of sockets, or
other raw files, should be forced to use descriptors
numbered above 256. This allows system functions such as
name services, to work as they depend upon stdio routines.
(See p 368 "erformance and Tuning - Java and the Internet".
There are limitations on the number of file descriptors
available to the current shell and its descendents. (See the ulimit
man page). The maximum number of file descriptors that can
be safely used for the shell and Solaris processes is 1024.
This limitation has been lifted for Solaris 7 64-bit.
Therefore the recommended maximum values to be added to /etc/system are:
set rlim_fd_cur=1024
set rlim_fd_max=1024
To use the limit command with csh:
% limit descriptors 1024
To use the ulimit command with Bourne or ksh:
$ ulimit -n 1024
However, some third-party applications need the max raised.
A possible recommendation would be to increase rlim_fd_max,
but not the default (rlim_fd_cur). Then rlim_fd_cur can be
raised on a per-process basis if needed, but the higher setting
for rlim_fd_max doesn't affect all processes.
2a. Using select() library function
-----------------------------------
The select(3C) library function uses a fixed-size
bitfield that can only handle 1024 file descriptors
unless on Solaris 7. The alternative is to use poll(2)
which has no limit. This is explained in the man pages.
For example, the following is an excerpt from the
select(3c) man page on Solaris 2.6:
% man -s3c select
C Library Functions select(3C)
...
NOTES
The default value for FD_SETSIZE (currently 1024) is larger
than the default limit on the number of open files. It is
not possible to increase the size of the fd_set data type
when used with select().
SunOS 5.6 Last change: 18 Apr 1997 4
All versions of Solaris (including Solaris 7 64-bit) have a default
"soft" limit of 64 and a "hard" limit of 1024.
The only way to safely raise the number of file descriptors
above 1024 is through the application and recompiling.
Solaris 7 allows upto 65536 fds passed to select() with
recompiling for a larger value of FD_SETSIZE.
The application needs to be compiled for 64-bit inorder
to get the larger FD_SETSIZE. You are limited to 1024
for a 32 bit application. Refer to /usr/include/sys/select.h.
However, developers can define a new FD_SETSIZE. A careful
reading of the man pages is necessary. From the select() man page
on Solaris 7:
% man -s3c select
C Library Functions select(3C)
...
NOTES
The default value for FD_SETSIZE (currently 1024) is larger
than the default limit on the number of open files. To
accommodate 32-bit applications that wish to use a larger
number of open files with select(), it is possible to
increase this size at compile time by providing a larger
definition of FD_SETSIZE before the inclusion of
<sys/types.h>;. The maximum supported size for FD_SETSIZE is
65536. The default value is already 65536 for 64-bit appli-
cations.
SunOS 5.7 Last change: 22 Apr 1998 4
3. Adjusting Pseudo-terminal Devices (ptys)
-------------------------------------------
Increasing ptys is accomplished by editing the /etc/system
file using the following syntax:
set pt_cnt=128
A reboot with the -r option is necessary to create the new
devices. If this option was not used, it is not necessary to reboot
again.The following commands can be used to create the new devices:
# drvconfig
# devlinks
Note: The parameter pt_cnt needs to be preset in the kernel at boot time
by way of the /etc/system file because the kernel sizes a structure based
on pt_cnt at boot If this is changed on a live kernel using the adb
command
or the crash command it can cause a system panic.
To verify the number of ptys do the following:
# cd /dev
# ls pty* | wc -l
# cd /dev/pts
# ls
The output from the ls command should show the highest number as 1 less
than the number of pty* in the /dev directory (because of zero).
(See the man page for pty and pts for more information.)
To see how many ptys are in use the crash command as root,
shown in this example:
# crash
dumpfile = /dev/mem, namelist = /dev/ksyms, outfile = stdout
>; pty
ptms_tty TABLE SIZE = 48
SLOT MWQPTR SWQPTR PT_BUFP TTYPID STATE
0 f5e84708 f5e84328 f5abcd08 243 mopen sopen
1 f5f2ad90 f5f2a9b0 f5abc498 291 mopen sopen
2 f5f2a3e0 f5f34ba8 f5f309c8 297 mopen sopen
3 f5f342f0 f5f4cca8 f5abc2b8 302 mopen sopen
4 0 f5f4c3f0 0 0 sopen
5 f5f568d0 f5f564f0 f5f30590 312 mopen sopen
6 f5933410 f5fdfad0 f605dcc8 1351 mopen sopen
>; q
The above output shows 6 ptys in use and the table size of 48
which is the default value. After increasing the pt_cnt parameter
in the /etc/system file and reboot the system, the table size
will reflect the new setting.
D. Performance and Database Tuning
1. Priority paging
------------------
Priority paging is new with Solaris 7 and was backported to
Solaris 2.6 (kernel patch 105181-09) and Solaris 2.5.1
(kernel patch 103640-25) and the equivalent x86 kernel
patches listed at the end of this article.
Priority paging provides an improved paging algorithm
which can significantly enhance system response when the file system
is being used. Priority paging introduces a new additional
water mark, cachefree. The paging parameters are now:
minfree < desfree < lotsfree < cachefree
By default the new behavior is turned off, so it is important
to enable this functionality on systems that are paging noticeably.
cachefree is set to lotsfree if priority_paging is not enabled.
If it is enabled then cachefree is set to 2 times lotsfree.
Adjusting this parameter makes switching between windows on
desktop systems faster, and is a big help for systems running
databases that read large files into memory from the filesystem.
If your system pages heavily, speed increases of several hundred percent
have been seen for compute-intensive jobs with a large dataset.
For more information on priority paging refer to the following URLs:
http://www.sunworld.com/swol-11-1998/swol-11-perf.html
http://www.sun.com/sun-on-net/performance/priority_paging.html
From INFODOC ID: 17946:
These tunables provide a mechanism to allow priority paging,
whereby filesystem pages will be paged out before application,
executable, and/or shared library pages. This can provide a
significant performance benefit when using applications which
perform frequent, random access to filesystem data which is
used once and then no longer required, by flushing filesystem
pages in preference to other types of pages.
By default, priority paging is disabled (priority_paging = 0);
it isenabled by adding the following line to the /etc/system
file and rebooting:
set priority_paging=1
The default value of cachefree depends on the value of the
priority_pagingtunable. If priority_paging is 0, then
cachefree is set equal to lotsfree.
If priority_paging=1, then cachefree is set to 2 times lotsfree.
When priority paging is enabled and free memory drops below
cachefree, the page scanner will start to run, but will only
mark pages used for filesystem data for pageout. If freemem
drops below lotsfree, the scanning algorithm performs just as
it did before, regardless of the setting of priority_paging.
cachefree can be adjusted by setting it in the /etc/system file;
if the value specified in /etc/system is less than lotsfree,
it will be set to lotsfree instead. Setting cachefree equal
to lotsfree is the equivalent to not having priority paging enabled.
A reboot is necessary.
2. Intimate Shared Memory (ISM)
-------------------------------
Large database applications on servers benefit from large
shared caches of data. By default, applications such as
Oracle, Informix, and Sybase use a special flag to specify
that they want intimate shared memory (ISM). ISM provides
for the shared memory to be locked and cannot be paged
out. Memory management data structures that are
normally created on a per process basis are created once and
then shared by every process. In Solaris 2.6 a further
optimization takes place as the kernel tries to find 4-Mbyte
contiguous blocks of physical memory that can be used as
pages to map the shared memory. This greatly reduces
memory management unit overhead. (p.333 "erformance and Tuning
- Java and the Internet"
Excerpts from "Shared memory uncovered" by Jim Mauro:
http://www.sunworld.com/sunworldonline/swol-09-1997/swol-09-insidesolaris-2.html
Intimate shared memory (ISM) is an optimization introduced
first in Solaris 2.2. It allows for the sharing of the translation
tables involved in the virtual to physical address translation
for shared memory pages, as opposed to just sharing the
actual physical memory pages. Typically, non-ISM systems maintain
a per-process mapping for the shared memory pages. With many processes
attaching to shared memory, this creates a lot of redundant
mappings to the same physical pages that the kernel must maintain.
Additionally, all modern processors implement some form of a translation
lookaside buffer (TLB), which is (essentially) a hardware cache
of address translation information. SPARC processors are no exception,
and, just like an instruction and data cache, the TLB has limits as to
how many translations it can maintain at any one time. As processes
get context switched in and out, we can reduce the effectiveness
of the TLB. If those processes are sharing memory, and we can share
the memory mappings also, we can make more effective use of the
hardware TLB.
...
Closing notes - Shared memory is a powerful and relatively simple
way to share data between processes. The use of shared memory by
applications requires setting the shared memory tunable parameters
to provide sufficient resources for the application. Hopefully,
the use and implementation of these tunables has been made clear.
Intimate shared memory is an important optimization that makes
more efficient use of the kernel and hardware resources
involved in the implementation of virtual memory and provides
a means of keeping heavily used shared pages locked in memory.
...
a. ISM Defaults
---------------
Intimate shared memory is enabled by default and there is no
need to edit the /etc/system file to turn on this feature. With a
currently patched kernel, turning off ISM can cause system
degradation and possibly a hang condition. In addition
database configuration files, such as Oracle's init.ora file,
should not have "use_ism=false" which turns it off.
b. Swap Configurations Related to Shared Memory
-----------------------------------------------
To understand swap configurations related to shared memory
see Sunworldonline, "Swap space implementation part 2"
also by Jim Mauro:
http://www.sun.com/sunworldonline/swol-01-1998/swol-01-insidesolaris.html
Here are some excerpts:
So, how much swap should be configured? Well, the basic requirement
for swap is driven directly by the amount of anonymous memory the
system needs to run the application. As we said earlier, if there
is enough physical RAM to hold all the required process pages,
then the system can run literally with no physical swap configured.
How much anonymous memory a system needs is not an easy thing to
determine with currently available tools. Your best bet is to use
the pmap command to examine process address space maps and measure
the heap and anon sizes. This is time consuming, but reasonably
accurate.
As an additional data point, experience has shown that large
applications (e.g., SAP/R3, BAAN, Oracle) tend to have processes
with large virtual address spaces. This is typically the result
of attaching to large shared memory segments used by relational
databases and large copy-on-write (COW) segments that get mapped
but sometimes never actually get touched. The net effect of this
is that on large systems supporting these commercial applications,
the virtual address space requirements grow to be quite large,
typically exceeding the physical memory size. Consequently,
such systems often require a fair amount of swap disk configured
to support many processes with large VA space running
concurrently. You need to configure 1 to 1.5 times the amount
of RAM you have for swap so the systems can fully utilize
all of the physical memory without running out of virtual
swap space.
3. Interprocess Communication Parameters (IPC)
----------------------------------------------
The values for the following IPC parameters need to be determined
by the Database Administrator (DBA). The Sun Solution Centers can
not give recommendations for what the actual IPC parameter
settings should be. These values are application dependent.
For Solaris releases previous to 2.6 more swap space, "backing
store" is needed for shared memory. Use swap -l. Divide the block
numbers by 2 to get megabytes. There should be atleast 2 times
the amount of swap for allocated shared memory (shmmax).
Here is the default and maximum values for shmmax:
Default Maximum
shmmax 1048576 (1Meg) 4294967295 (4GB) 2.5.1, 2.6, 32bit solaris 7
2147483647 (2GB) 2.5 or lower
Solaris 2.6 shmmax and shmmin are unsigned ints (32 bit).
Solaris 7 "32-bit" shmmax and shmmin are unsigned ints (32 bit).
Solaris 7 "64-bit" shmmax and shmmin are unsigned longs (64 bit).
In all cases, shmmni and shmseg are signed ints (31 bit).
shmmax limits the maximum size of a shared memory segment, which is the
largest value which can be requested of shmget(2). The resource it controls
is not preallocated. It is allocated on demand.
Solaris 7 64-bit breaks the 4GB barrier. The maximum size is theoretical.
The actual settings need to be based on the system resources like
memory and database sizes and configurations. The maximum size of
the segment itself (shmmax) is just an upper limit.
******
See REFERENCES A. IPC articles available in the SunSolve collections
See REFERENCES B. More SunWorld Online Articles
See REFERENCES C. New Book on Oracle8 and Unix Performance Tuning
******
-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
3a, 3b and 3c below show examples of the syntax for setting
IPC parameters in the /etc/system file using decimal values.
Hex values can also be used but would need to be preceeded with "0x".
3a. Shared Memory Parameters
----------------------------
Example of shared memory parameters in /etc/system:
#
set shmsys:shminfo_shmmax=1048576000
set shmsys:shminfo_shmmin=1
set shmsys:shminfo_shmmni=200
set shmsys:shminfo_shmseg=10
#
The above parameters are displayed in the order in which they appear
in the /usr/include/sys/shm.h file on Solaris 2.6 and Solaris 7.
The header files, shm.h, sem.h and smg.h, are included below
to demonstrate the following:
1) show the exact parameter name
2) show the definition of each parameter
3) show how to construct the syntax for
adding an IPC parameter to the /etc/system file
For example, setting the maximum shared memory segment size
in the /etc/system file would be as follows:
set shmsys:shminfo_shmmax = <decimal or hex number>;
shmsys:shminfo_shmmax is constructed from:
shm (header file name - shm.h)
sys (directory abbreviation -/usr/include/sys)
shminfo (the structure name - struct shminfo)
shmmax (a parameter in struct shminfo)
From /usr/include/sys/shm.h:
struct shminfo {
size_t shmmax, /* max shared memory segment size */
shmmin; /* min shared memory segment size */
int shmmni, /* # of shared memory identifiers */
shmseg; /* max attached shared memory */
/* segments per process */
};
Note that a type "size_t" is different on Solaris 2.6 and Solaris 7:
Solaris 2.6 /usr/include/sys/types.h:
#ifndef _SIZE_T
#define_SIZE_T
typedefuint_tsize_t;/* len param for string funcs */
#endif
Solaris 7 /usr/include/sys/types.h:
#ifndef _SIZE_T
#define _SIZE_T
#if defined(_LP64) || defined(_I32LPx)
typedef ulong_t size_t; /* size of something in bytes */
#else
typedef uint_t size_t; /* (historical version) */
#endif
#endif /* _SIZE_T */
3b. Semaphore Parameters
------------------------
Example of a semaphore parameter in /etc/system:
#
set semsys:seminfo_semmap=15
#
From /usr/include/sys/sem.h:
/*
* Semaphore information structure
*/
struct seminfo {
int semmap; /* # of entries in semaphore map */
int semmni; /* # of semaphore identifiers */
int semmns; /* # of semaphores in system */
int semmnu; /* # of undo structures in system */
int semmsl; /* max # of semaphores per id */
int semopm; /* max # of operations per semop call */
int semume; /* max # of undo entries per process */
int semusz; /* size in bytes of undo structure */
int semvmx; /* semaphore maximum value */
int semaem; /* adjust on exit max value */
};
3c. Message Queue Parameters
---------------------------
Example of a message queue parameter in /etc/system:
#
set msgsys:msginfo_msgmap=150
#
From /usr/include/sys/msg.h:
/*
* Message information structure.
*/
struct msginfo {
int msgmap; /* # of entries in msg map */
int msgmax; /* max message size */
int msgmnb; /* max # bytes on queue */
int msgmni; /* # of message queue identifiers */
int msgssz; /* msg segment size (should be word size */
/* multiple) */
int msgtql; /* # of system message headers */
ushort_t msgseg; /* # of msg segments (MUST BE < 3276 */
};
******
See REFERENCES A. IPC articles available in the SunSolve collections
See REFERENCES B. More SunWorld Online Articles
See REFERENCES C. New Book on Oracle8 and Unix Performance Tuning
******
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发表于 2002-06-14 18:00
