labview performance and memory management

7/24/2019 LabVIEW Performance and Memory Management

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Dev Days Performance

and Memory Management

Adam Kemp

Sta Software EngineerLabVIE !ompi"er #eam


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$oa"s

%nderstand t&e LabVIE E'ec(tionSystem

Learn to improve performance by) *ed(cing data copies

*ed(cing overa"" memory (sage

%nderstand VI E'ec(tion Properties


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#&e LabVIE E'ec(tionSystem

#&e e'ec(tion system is t&e part ofLabVIE w&ic& is responsib"e foract(a""y r(nning yo(r code

Enab"es a(tomatic para""e"ism

%ni+(e to LabVIE ,t&er "ang(ages re+(ire man(a" t&read

management


4/40

#&e LabVIE E'ec(tionSystem

or-s "i-e a t&read poo" A +(e(e of .obs

A set of t&reads p(""ing .obs o t&e +(e(e

/obs 01+(e(e e"ements23 are pieces of VI code to

e'ec(te ,ne +(e(e per e'ec(tion system

%I

Standard

Instr(ment I4,

Data Ac+(isition

,t&er 5

,t&er 6

#imed "oops


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LabVIE E'ec(tion System

Eac& e'ec(tion system &as m("tip"et&reads

E'ception) %I &as on"y one t&read


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LabVIE E'ec(tion System


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LabVIE !"(mpingA"gorit&mClump 1

Clump 2

Clump 0 Clump 0


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!"(mp 6 S"eeping

!"(mp 5 S"eeping

!"(mp 7 S"eeping

LabVIE !"(mpingA"gorit&m

!omp"etion ofdiagram)Divide nodes8 disp"ayofindicators8 t&en VIe'it9

Start of diagram)*eads contro"s8 t&ensc&ed("es !"(mps 5and 6#&en s"eeps999

:ottom ;or Loop

Indicator is(pdated!"(mp 7Sc&ed("edS"eep999

#op ;or LoopIndicator is(pdated!"(mp 7Sc&ed("ed

S"eep999

Clump 1

Clump 2

Clump 0


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$oing to s"eep

&en a node 1goes to s"eep2 it p(ts itse"f on await +(e(e and t&en ret(rns to t&e e'ec(tionsystem E9g98


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Preferred E'ec(tion Systems

Some nodes m(st r(n in %I t&read

Eac& VI can specify a preferrede'ec(tion system Defa("t is 1Same as ca""er2


11/40

Switc&ing E'ec(tionSystems

=appens w&en code needs to r(n in a dierente'ec(tion system t&an t&e ca""er or previo(s code

Most common wit& %I code

Switc&ing e'ec(tion systems can ca(seperformance prob"ems *e+(ires going to s"eep and t&en wa-ing (p on anot&er

e'ec(tion system t&read

Switc&ing bac- ta-es .(st as "ong

!an sometimes set Preferred E'ec(tion System toavoid e'tra switc&es

Avoid (nnecessary %I code


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Priorities

S(bVI priorities aect t&e priority of t&e +(e(ee"ements for t&at VI wit&in an e'ec(tionsystem

=ig&er priority +(e(e e"ements are p(""ed o>rst

#&e priority setting does not aect t&e priorityof t&e e'ec(tion system t&read itse"f#&e ,S may preempt t&e w&o"e t&read to r(n t&et&read for anot&er e'ec(tion system 0or ot&erprocess3

%se #imed Loops to contro" priority more re"iab"y


13/40

S(bro(tine Priority

?ot a rea" priority

*ed(ces e'ec(tion system over&ead for verycommon"y ca""ed code

;orces t&e w&o"e VI to be in a sing"e c"(mp Prevents t&e VI from ever going to s"eep

?o ca""s w&ic& may s"eep 0"i-e +(e(e operations3

?o switc&ing e'ec(tion systems

!an on"y ca"" ot&er s(bro(tine VIs

?o para""e"ism

!an be set to 1S-ip S(bro(tine !a"" If :(sy2

%s(a""y not recommended


14/40

In"ine VIs

Preferred rep"acement for S(bro(tine Priority

Entire b"oc- diagram is inserted into ca""er w&ent&e ca""er is compi"ed @ero ca"" over&ead

!an sti"" contain para""e"ism

A""ows for more compi"er optimiations

Limitations)

?o front pane" access ?ot a"" nodes a""owed

;orces ca""ers to recompi"e every time t&e S(bVI ismodi>ed


15/40

ire Semantics

Every wire is a b(er :ranc&es create copies


16/40

,ptimiations by LabVIE

#&e t&eoretica" B copies become 5 copyoperation9

Copy

Output is inplace with input


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#&e 1In P"ace2 A"gorit&m

Determines w&en a copy needs to bemade eig&ts arrays and c"(sters &ig&er t&an

ot&er types A"gorit&m r(ns before e'ec(tion

Does not -now t&e sie of an array or string

*e"ies on t&e se+(entia" aspects of t&e

program :ranc&es mig&t re+(ire copies


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:ottom %p

In p"ace information is propagatedbottom (p t&ro(g& t&e ca""&ierarc&y

Increments array in place

Copy because

of increment No copies required

Branched wire


19/40

S&owing :(er A""ocations


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E'amp"e of In P"ace,ptimiation

Operate on each element of an arrayof waveforms


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Ma-e t&e >rst S(bVI 1inp"ace2

c&anges intoC


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S(bVI 6 is made 1in p"ace2

c&angesintoC


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S(bVI is made 1in p"ace2

c&angesintoC


24/40

;ina" *es("t) Dots are=idden


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In P"ace E"ement Str(ct(re?odes

Seven border node types)

Array inde'4rep"ace

Array sp"it4rep"ace s(barrays

%nb(nd"e4:(nd"e c"(ster

%nb(nd"e4:(nd"e waveform Variant to4from e"ement

In P"ace In4o(t border node

Data Va"(e *eference *ead4rite

*ig&tc"ic- "eft or rig&t border to add nodes


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Pane" Data or ,perate:(ers

!ontro"s andindicators &avet&eir own copy of

t&e data Memory is not

needed if t&e frontpane" is not in

memory Defa("t data

increases memory

(sage


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#ransfer :(ers

#ransfer :(ersprotect data transferbetween ,perate and

E'ec(tion :(ers ,n"y (pdated if front

pane" is in memory

Copy

Copy


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Loca" and $"oba" Variab"es

Loca" variab"es (pdate t&e datatransfer b(er9

*eading a "oca" or g"oba" variab"e

a"ways ca(ses a data copy %se wires to transfer data w&en

possib"e


29/40

Loca" Variab"es vs9 VI Server Property

?ode

Loca" Variab"es !an r(n in any t&read

!opies to4from transfer b(er

rites ca(se second copy into operate b(er if front pane" isin memory 0avoid t&is if possib"e3

%se w&en speed is important

Property ?odes M(st r(n in %I t&read

!opies to4from operate b(er

rites ca(se second copy into transfer b(er

;orce front pane" in memory

%se w&en sync&rono(s disp"ay is necessary

Avoid both if possible


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Data by *eference

Manip("ate references to t&e data insteadof t&e data itse"f

Data Copy

Data Copy

Data

Reference

Reference

Reference

Traditional dataow) branc&esmay create copies

By reference) points tomemory "ocation


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Data Va"(e *eferences

Act as references to data rat&er t&anf("" data itse"f

!an protect access to data


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Memory *ea""ocation

Prea""ocate anarray if yo()

!onditiona""yadd va"(es to

an array !an determine

an (pper "imiton t&e array

sie


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!onditiona" Indicators

An indicator inside a !ase str(ct(reor ;or Loop

Prevents LabVIE from re(sing datab(ers


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*eentrancy and Dataspaces

?onreentrant ,ne dataspace s&ared by every ca""

,n"y one ca"" can e'ec(te at a time

Lower memory (sage

!an save state 0e9g98 for LV6sty"e g"oba"s3

Standard reentrancy8 a-a 1Prea""ocate c"ones2) Every ca"" &as its own dataspace

!a""s never &ave to wait

Poo"ed reentrancy8 a-a 1S&are c"ones2 Added in LabVIE F9B

Eac& ca"" p(""s a dataspace from a s&ared poo" ?ew dataspaces are a""ocated dynamica""y if needed

!a""s never &ave to wait 0e'cept possib"y to a""ocate a new dataspace3

*e+(ired for rec(rsion


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LabVIE !"ean(p

LabVIE c"eans (p many referencesw&en t&e owning VI goes id"e and ot&ersw&en t&e process c"oses

Man(a""y c"ose references to avoid(ndesirab"e memory growt&8 partic("ar"yfor "ongr(nning app"ications9


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Memory %sage of t&e %ser Interface

Every contro" on t&e %I re+(ires memoryin order to store t&e data str(ct(re

At r(n time8 !ontro" and Indicator data is

additiona" copy of b"oc- diagram data Defa("t data for contro"s may contrib(te

to (nnecessary memory (sage

S(bVI %Is genera""y do not contrib(te tomemory (sage


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#ips for red(cing memory(sage

,perate on data in p"ace

Do not over(se reentrant settings

!"ose references to avoid "ea-s

Avoid operations w&ic& re+(ire t&e front pane" tobe in memory E') !ontro" references

Save t&e VI and c"ose t&e front pane" before r(nning

Avoid "arge defa("t data in arrays8 grap&s8 etc9

,n"y disp"ay information on t&e front pane" w&ennecessary

*e+(est Dea""ocation Primitive


38/40

Memory ;ragmentation

59G $: 79H $:

%sedAvai"ab"e795 $: 795G $:

79H$:

795G $: 79H6 $: 79F$:

79 $:

795H $:

*eported

Act(a"


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$enera" :enc&mar-ing tips

Disab"e deb(gging

Save a""

!"ose a"" (nnecessary front pane"s


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labview performance and memory management

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