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madv.so.1(1)
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 mad‐
vise(3C) to specify memory access patterns:
normal
random
sequential
access_lwp
access_many
access_many_pset
access_default
MADVCFGFILE=config-file
config-file is a text file which contains one or more madv configu‐
ration entries of the form:
exec-name exec-args:advice-opts
Advice specified in config-file takes precedence over that speci‐
fied 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 getex‐
ecname(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
ATTRIBUTES
See attributes(7) for descriptions of the following attributes:
tab() box; cw(2.75i) |cw(2.75i) lw(2.75i) |lw(2.75i) ATTRIBUTE TYPEAT‐
TRIBUTE VALUE _ Availabilitysystem/core-os _ Interface StabilityUncom‐
mitted
SEE ALSO
cat(1), ld.so.1(1), proc(1), sh(1), brk(2), exec(2), fork(2), memc‐
ntl(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 runtime linker or by system
libraries making direct system calls (for example, allocations for
thread stacks) are not affected.
Oracle Solaris 11.4 11 May 2021 madv.so.1(1)