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 vari-
ables:
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 exe-
cutable. 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 MAD-
VERRFILE 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 seg-
ments for application /usr/bin/foo:
example$ LD_PRELOAD=$LD_PRELOAD:madv.so.1
example$ MADVCFGFILE=madvcfg
example$ export LD_PRELOAD MADVCFGFILE
example$ cat $MADVCFGFILE
/usr/bin/foo:ism=access_lwp
Example 2: Setting advice for all applications with excep-
tion
The following configuration sets advice for all applications
with the exception of ls.
example$ 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 $MADVCFGFILE
foo*:madv=access_many,heap=sequential,shm=access_lwp
Example 5: Applying advice selectively
The following configuration applies advice for the heap of
applications beginning with ora that have ora1 as an argu-
ment:
example$ 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
ATTRIBUTES
See attributes(5) for descriptions of the following attri-
butes:
____________________________________________________________
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
|_____________________________|_____________________________|
| Availability | SUNWesu (32-bit) |
|_____________________________|_____________________________|
| | SUNWesxu (64-bit) |
|_____________________________|_____________________________|
| Interface Stability | Unstable |
|_____________________________|_____________________________|
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.
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