MADV.SO.1(1) User Commands MADV.SO.1(1)

NAME

madv.so.1 - madv library

SYNOPSIS

/usr/lib/madv.so.1

DESCRIPTION

The madv.so.1 shared object provides a means by which the VM advice can
be selectively configured for a launched process (or processes) and its
descendants. To enable madv.so.1, the following string needs to be
present in the environment (see ld.so.1(1)) along with one or more MADV
environment variables:

LD_PRELOAD=$LD_PRELOAD:madv.so.1

ENVIRONMENT VARIABLES

If the madv.so.1 shared object is specified in the LD_PRELOAD list, the
following environment variables are read by the madv shared object to
determine to which created process(es) to apply the specified advice.

MADV=advice
MADV specifies the VM advice to use for all
heap, shared memory, and mmap regions in the
process address space. This
advice is applied to all created processes.

Values for advice correspond to values in
<sys/mman.h> used in madvise(3C) to specify
memory access patterns:
normal
random
sequential
access_lwp
access_many
access_default


MADVCFGFILE=config-file
config-file is a text file which contains one
or more madv configuration entries of the
form:

exec-name exec-args:advice-opts


Advice specified in config-file takes
precedence over that specified by the MADV
environment variable. When MADVCFGFILE is not
set, advice is taken from file /etc/madv.conf
if it exists.

exec-name specifies the name of an application
or executable. The corresponding advice is set
for newly created processes (see
getexecname(3C)) that match the first exec-
name found in the file.

exec-name can be a full pathname, a base name,
or a pattern string. See File Name Generation
in sh(1) for a discussion of pattern matching.

exec-args is an optionally specified pattern
string to match against arguments. Advice is
set only if exec-args is not specified or
occurs within the arguments to exec-name.

advice-opts is a comma-separated list
specifying the advice for various memory
region(s):

madv=advice
Applies to all heap,
shared memory, and mmap
regions in the process
address space.


heap=advice
The heap is defined to be
the brk area (see
brk(2)). Applies to the
existing heap and for any
additional heap memory
allocated in the future.


shm=advice
ism=advice
dism=advice
Shared memory segments
(see shmat(2)) attached
using any flags, flag
SHM_SHARE_MMU, or flag
SHM_PAGEABLE
respectively. Options ism
and dism take precedence
over option shm.


map=advice
mapshared=advice
mapprivate=advice
mapanon=advice
Mappings established
through mmap(2) using any
flags, flag MAP_SHARED,
flag MAP_PRIVATE, or flag
MAP_ANON, respectively.
Options mapshared,
mapprivate, and mapanon
take precedence over
option map. Option
mapanon takes precedence
over mapshared and
mapprivate.


MADVERRFILE=pathname
By default, error messages are logged via
syslog(3C) using level LOG_ERR and facility
LOG_USER. If MADVERRFILE contains a valid
pathname (such as /dev/stderr), error messages
will be logged there instead.

EXAMPLES

Example 1: Applying advice to all ISM segments

The following configuration applies advice to all ISM segments for
application /usr/bin/foo:


example$ LD_PRELOAD=$LD_PRELOAD:madv.so.1
example$ MADVCFGFILE=madvcfg
example$ export LD_PRELOAD MADVCFGFILE
example$ cat $MADVCFGFILE
/usr/bin/foo:ism=access_lwp

Example 2: Setting advice for all applications with exception

The following configuration sets advice for all applications with the
exception of ls.


example$ LD_PRELOAD=$LD_PRELOAD:madv.so.1
example$ MADV=access_many
example$ MADVCFGFILE=madvcfg
example$ export LD_PRELOAD MADV MADVCFGFILE
example$ cat $MADVCFGFILE
ls:

Example 3: Precedence rules (continuation from Example 2)

Because MADVCFGFILE takes precedence over MADV, specifying '*' (pattern
match all) for the exec-name of the last madv configuration entry would
be equivalent to setting MADV. The following is equivalent to example 2:


example$ LD_PRELOAD=$LD_PRELOAD:madv.so.1
example$ MADVCFGFILE=madvcfg
example$ export LD_PRELOAD MADVCFGFILE
example$ cat $MADVCFGFILE
ls:
*:madv=access_many

Example 4: Applying advice for different regions

The following configuration applies one type of advice for mmap regions
and different advice for heap and shared memory regions for a select set
of applications with exec names that begin with foo:


example$ LD_PRELOAD=$LD_PRELOAD:madv.so.1
example$ MADVCFGFILE=madvcfg
example$ export LD_PRELOAD MADVCFGFILE
example$ cat $MADVCFGFILE
foo*:madv=access_many,heap=sequential,shm=access_lwp

Example 5: Applying advice selectively

The following configuration applies advice for the heap of applications
beginning with ora that have ora1 as an argument:


example$ LD_PRELOAD=$LD_PRELOAD:madv.so.1
example$ MADVCFGFILE=madvcfg
example$ export LD_PRELOAD MADVCFGFILE
example$ cat $MADVCFGFILE
ora* ora1:heap=access_many

FILES

/etc/madv.conf
Configuration file

SEE ALSO

cat(1), ld.so.1(1), proc(1), sh(1), brk(2), exec(2), fork(2), mmap(2),
memcntl(2), shmat(2), getexecname(3C), madvise(3C), syslog(3C), proc(4),
attributes(5)

NOTES

The advice is inherited. A child process has the same advice as
its parent. On exec() (see exec(2)), the advice is set back to the
default system advice unless different advice has been configured via the
madv shared object.


Advice is only applied to mmap regions explicitly created by the user
program. Those regions established by the run-time linker or by system
libraries making direct system calls (for example, libthread allocations
for thread stacks) are not affected.


February 15, 2002 MADV.SO.1(1)