pmadvise

- applies advice about memory to a process

Synopsis

pmadvise -o option[,option] [-F] [-l] [-v] pid...

Description

pmadvise applies advice about how memory is used in the specified process using madvise(3C).

pmadvise allows users to apply advice to a specific sub-range at a specific instant in time. pmadvise differs from madv.so.1(1) in that madv.so.1(1) applies the advice throughout execution of the target program to all segments of a specified type.

Options

The following options are supported:

-F

Force by grabbing the target process even if another process has control.

You should exercise caution when using the -F option. See proc(1).

-l

Show unresolved dynamic linker map names.

-o

Specify advice to apply in the following form:

private=advice
shared=advice
heap=advice
stack=advice
address[:length]=advice

where the advice can be one of the following:

normal
random
sequential
willneed
dontneed
free
access_lwp
access_many
access_many_pset
access_default

An address and length can be given to specify a subrange to apply the advice. The address should be hexadecimal and the length should be in bytes by default.

If length is not specified and the starting address refers to the start of a segment, the advice is applied to that segment. length can be qualified by K, M, G, T, P, or E to specify kilobytes, megabytes, gigabytes, terabytes, or exabytes respectively as the unit of measure.

-v

Print verbose output. Display output as pmap(1) does, showing what advice is being applied where. This can be useful when the advice is being applied to a named region (for example, private, shared, and so forth) to get feedback on exactly where the advice is being applied.

pmadvise tries to process all legal options. If an illegal address range is specified, an error message is printed and the offending option is skipped. pmadvise quits without processing any options and prints a usage message when there is a syntax error.

If conflicting advice is given on a region, the order of precedence is from most specific advice to least, that is, most general. In other words, advice specified for a particuliar address range takes precedence over advice for heap and stack which in turn takes precedence over advice for private and shared memory.

Moreover, the advice in each of the following groups are mutually exclusive from the other advice within the same group:

MADV_NORMAL, MADV_RANDOM, MADV_SEQUENTIAL
MADV_WILLNEED, MADV_DONTNEED, MADV_FREE
MADV_ACCESS_DEFAULT, MADV_ACCESS_LWP, MADV_ACCESS_MANY

Operands

The following operands are supported:

pid

Process ID.

Examples

Example 1 Applying Advice to a Segment at Specified Address

The following example applies advice to a segment at a specified address:

% pmap $$
100666: tcsh
00010000     312K r-x--  /usr/bin/tcsh
0006C000      48K rwx--  /usr/bin/tcsh
00078000     536K rwx--    [ heap ]
FF100000     856K r-x--  /lib/libc.so.1
FF1E6000      32K rwx--  /lib/libc.so.1
FF1EE000       8K rwx--  /lib/libc.so.1
FF230000     168K r-x--  /lib/libcurses.so.1
FF26A000      32K rwx--  /lib/libcurses.so.1
FF272000       8K rwx--  /lib/libcurses.so.1
FF280000     576K r-x--  /lib/libnsl.so.1
FF310000      40K rwx--  /lib/libnsl.so.1
FF31A000      24K rwx--  /lib/libnsl.so.1
FF364000       8K rwxs-    [ anon ]
FF370000      48K r-x--  /lib/libsocket.so.1
FF38C000       8K rwx--  /lib/libsocket.so.1
FF3B0000     176K r-x--  /lib/ld.so.1
FF3EC000       8K rwx--  /lib/ld.so.1
FF3EE000       8K rwx--  /lib/ld.so.1
FFBE6000     104K rw---    [ stack ]
%
% pmadvise -o 78000=access_lwp $$

%

Example 2 Using the -v Option

The following example displays verbose output from pmadvise:

 
% pmadvise -o heap=access_lwp,stack=access_default -v $$
1720:   -sh
00010000      88K r-x--  /usr/sbin/sh
00036000       8K rwx--  /usr/sbin/sh
00038000      16K rwx--    [ heap ]           <= access_lwp
FF250000      24K r-x--  /lib/libgen.so.1
FF266000       8K rwx--  /lib/libgen.so.1
FF272000       8K rwxs-    [ anon ]
FF280000     840K r-x--  /lib/libc.so.1
FF362000      32K rwx--  /lib/libc.so.1
FF36A000      16K rwx--  /lib/libc.so.1
FF390000      64K rwx--    [ anon ]
FF3B0000     168K r-x--  /lib/ld.so.1
FF3EA000       8K rwx--  /lib/ld.so.1
FF3EC000       8K rwx--  /lib/ld.so.1
FFBFE000       8K rw---    [ stack ]          <= access_default

Exit Status

The following exit values are returned:

0

Successful completion.

non-zero

An error occurred.

Files

/proc/*

Process files

/usr/prob/lib/*

proc tools support files

Attributes

See attributes(5) for descriptions of the following attributes:

The command syntax is Committed. The output formats are Uncommitted.

See Also

madv.so.1(1), pmap(1), proc(1), madvise(3C), attributes(5)