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| Define your load-average support |
port, edit sendmail/conf.h |
The load average is the average number of blocked processes
(processes that are runnable but not able to run because of a lack of
resources) over the last minute. The sendmail
program can vary its behavior appropriately as the load average
changes. Thresholds for change are defined by the options shown in
Table 24-9.
The method that is used to get the current load average from the
operating system varies widely. This LA_TYPE definition determines
which method to use. It is correctly defined inside
sendmail/conf.h for all currently supported
operating systems. Porting sendmail to a new
system might require that you define LA_TYPE yourself. The possible
values and their meanings are shown in Table 3-5.
Table 3-5. LA_ Methods for getting the load average
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LA_ZERO
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Always returns 0. Essentially disables load average checking. This is
portable to all systems.
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LA_INT
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Read /dev/kmem for the symbol
avenrun. If found, interpret the result as a
native (usually long) integer.
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LA_FLOAT
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Read /dev/kmem for the symbol
avenrun. If found, interpret the result as a
floating-point value.
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LA_SHORT
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Read /dev/kmem for the symbol
avenrun. If found, interpret the result as a
short integer.
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LA_SUBR
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Call the library routine getloadavg(3) and use
the result returned.
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LA_MACH
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Call the MACH-specific processor_set_info(2)
routine and use the result returned.
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LA_PROCSTR
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Read the Linux-specific /proc/loadavg file and
interpret the result as a floating-point value.
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LA_READKSYM
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Use the (some SysV versions) ioctl of
MIOC_READKSYM to read /dev/kmem.
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LA_DGUX
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DG/UX-specific support for using the
dg_sys_info(2) function to read the load
average.
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LA_HPUX
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HP-UX specific support for using the
pstat_getdynamic(2) function to read the load
average.
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LA_IRIX6
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Irix 6.x-specific support that adapts to 32- or 64-bit kernels. This
is, otherwise, similar to LA_INT.
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LA_KSTAT
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Solaris specific support for using the kstat(2)
function to read the load average.
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LA_DEVSHORT
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Read a short from a system file and scale it in the same manner as
LA_SHORT. The default file is
/dev/table/avenrun.
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The LA_INT, LA_SHORT, LA_FLOAT, and LA_READKSYM settings require
additional tuning. For these, three additional definitions are used,
as shown in Table 3-6.
Table 3-6. Tuning for LA_INT, LA_SHORT, LA_FLOAT, and LA_READKSYM
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FSHIFT
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Number of bits to shift right when using LA_INT, LA_SHORT, and
LA_READKSYM. Default is 8.
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_PATH_UNIX
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The pathname of your kernel. This is required for LA_INT and
LA_SHORT. Default is /unix for SysV;
/hp_ux for HP-UX V9;
/stand/unix for HP-UX V10, News, and UXP/OS;
/dev/ksyms for Solaris;
/dynix for DYNIX; otherwise
/vmunix.
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_PATH_KMEM
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The pathname of your kernel memory. This is required for LA_INT,
LA_SHORT, LA_FLOAT, and LA_READKSYM. Default is
/dev/kmem.
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LA_AVENRUN
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The name of the kernel variable that holds the load average. Used by
LA_INT, LA_SHORT, and LA_FLOAT. Default is
averun for SysV, otherwise
_averun.
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NAMELISTMASK
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The mask to bitwise-AND against the return value of
nlist(3). If this is undefined, the return value
is used as is. A common value is 0x7fffffff to strip off the high
bit.
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New ports should be reported to
sendmail@sendmail.org so that they can be folded
into future releases.
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