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),
memcntl(2), mmap(2), shmat(2), getexecname(3C), madvise(3C),
syslog(3C), proc(5), attributes(7)

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)