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C ache Analyzer
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Cache Analyzer
Technical Information
Cache Analyzer
s Basic support for all microcontrollers
s Advanced support for ARM architecture
s Optimize instruction and data cache usage
s Find bus transfer bottlenecks
s Verify effects of code optimisation
s Simulate effects of different cache sizes
s Various graphical and numerical displays
The cache analysis tool provides developers of embedded
systems with the following benefits:
1) Optimization of program run times
2) Reduction in power consumption of the entire system
Cache analysis can be performed on all microcontrollers,
cache architectures, and cache hierarchies. If required,
the predefined cache structure of microcontrollers can
Cache Analyzer
also be modified. In this way, an alternative cache struc-
ture can be tested to
determine if its use will lead to greater cache efficiency
and therefore shorten program run times. The result can
then be taken into account for future designs.
26.03.10
TRACE32 - Technical Information 2
Cache Analyzer
Overview
Microcontrollers that operate at rates of the TRACE32-PowerTrace micropro-
more than 200 MHz can only achieve cessor development tool is used to
optimum program run times in embed- analyze the relationship between
ded systems if their caches are used cache efficiency and program run
efficiently. This article describes how times.
Introduction
A cache is a small, fast memory that is gram instructions or data items
generally integrated directly in the required because of its small size (128
microcontroller. Individual program KB to 1 MB). As a result, various parts
parts are temporarily stored in the of the program compete for space in
cache so that the microcontroller does the cache and evict each other. The
not have to retrieve each program cache structure determines which pro-
instruction or data item from the slow gram parts compete for a place in the
external memory. However, the cache cache and constantly replace other
can only store a limited number of pro- program parts.
Cache Addressing
Short sections of program (usually 16
or 32 bytes) can be temporarily stored Cache addressing uses the memory
in a cache line to enable quick access. address to determine in which cache
Cache addressing, which is defined by line the required program part is to be
the cache structure, determines in temporarily stored. The analyses dis-
which cache line the instructions and cussed in this article use a 2-way set
data items of individual memory associative cache. In a 2-way set asso-
addresses are stored. As the memory ciative cache two cache lines are
address mapping on the cache line allowed to hold the instructions or data
provides the basis for analyzing cache of a memory address.
efficiency, it is necessary to understand
the process of cache addressing.
Cache Analyzer
Cache Analyzer
TRACE32 - Technical Information 3
Tag Cache line
Tag Cache line
Figure 1: Diagram of a 2-way associative cache
❏ Bits [12..4] are used to select the
The given example of a cache has the cache line (9 bits for 512 cache
following data: lines)
❏ 16 bytes per cache line ❏ Bits [31..13] are entered as the
tag in the cache line. The bits
❏ 512 cache lines [31..13] of a memory address are
compared with the tag to
Using this data, a 32-bit memory is determine whether a program
mapped as follows to a cache line: instruction or data item is already
stored in a cache line.
❏ Bits [3..0] are used to determine
the address of the word/byte
within the cache line
(4 bits for 16 bytes per cache line)
31 13 12 4 3 0
Word/byte in the
Tag entry Cache line selection
cache line
Figure 2: In the example of a cache, the bits [12..4] of the memory address
determine in which cache line the program instructions/data items are
to be temporarily stored.
This type of cache addressing means
that all program parts that match the
address defined in bits [12..4] are
stored in the same cache line. For
example, the following memory
addresses are competing for the cache
line 0x15:
0x8150: 0000 0000 0000 0000
100 0 0001 0101 0000
0xA150: 0000 0000 0000 0000
101 0 0001 0101 0000
Cache Analyzer
Cache Analyzer
TRACE32 - Technical Information 4
0xC150: 0000 0000 0000 0000 times slower than when the data
110 0 0001 0101 0000 is stored in the cache. Each time
the external memory is accessed,
If three or more addresses compete for the program execution time slows
the same cache line in a 2-way asso- down considerably.
ciative cache, the memory contents of ❏ Each time the external memory is
the address are repeatedly evicted accessed, the power
from the cache. When an entry is consumption of the entire system
replaced, the evicted cache contents increases immediately by a
have to be reloaded into the cache significant level . This is a great
when the program requires them again. disadvantage for portable,
battery-powered devices.
The contents have to be accessed from
the external memory each time. This is
The best way to reduce the frequency
to be avoided if possible for the follow-
with which the external memory is
ing reasons:
accessed, is to prevent unnecessary
❏ Current access times for external eviction from the cache. Unnecessary
memories show that the rate at eviction always occurs when several
which an instruction or data item memory addresses compete for a lim-
is retrieved from the external ited number of cache lines, while other
memory, is on average, 10 to 30 cache lines are hardly being used, if at
all.
Figure 3: Several memory addresses compete for a limited number of cache
lines, while other cache lines are hardly used.
Cache Analyzer
Cache Analyzer
TRACE32 - Technical Information 5
Cache efficiency can be optimized by ory in such a way that competition for
modifying the relocation information in cache lines is distributed as evenly as
the linker command file so that func- possible.
tions and data are placed in the mem-
Figure 4: Competition for cache lines is distributed evenly.
cache. Since October 2004, Lauter-
Before developers of embedded bach Datentechnik GmbH has provided
designs can optimize the positioning of a cache analysis tool for its TRACE32-
functions and data in the memory, they PowerTrace microprocessor develop-
require an analysis tool that can trace ment system.
any unnecessary eviction from the
Cache Analysis
Before describing how to carry out a ❏ Cache miss: An instruction or
cache analysis, here is a short defini- data item required by the
tion of some important terms: program that is not located in the
cache and therefore has to be
❏ Cache hit: An instruction or data loaded from the external memory.
item required by the program that
is located in the cache. ❏ Cache victim: An instruction or
data item evicted from the cache,
in order to create a cache miss
place for the program part
currently required.
Cache Analyzer
Cache Analyzer
TRACE32 - Technical Information 6
The following steps are required to ture
carry out a cache analysis using
TRACE32-PowerTrace for a selected The TRACE32 software identifies the
system function (for example, image cache structure of the microcontroller
compression for a cellular telephone): used in the target system. The instruc-
tion cache (IC) has the same cache
structure as the cache structure
Identifying the cache struc- described in the introduction.
Figure 5: Automatic definition of the cache structure of the microcontroller
Evaluating the results of the
The software can identify all cache analysis
structures and cache hierarchies cur-
rently available on the market, includ- Cache analysis determines the cache
ing level 2/level 3 caches. TRACE32 hit, cache miss, and cache victim rates
also supports cache structures that for the recorded program and data flow
have been configured using a memory based on the defined cache structure.
protection unit (MPU) or a memory
management unit (MMU). To avoid unnecessary eviction from the
cache, the following information is
required:
Recording program and data
❏ Which cache lines have a
flow in the trace memory particularly high cache victim
Cache analysis is based on the pro- rate?
gram and data flow recorded in the ❏ Which parts of the program are
trace memory. TRACE32-PowerTrace competing for these lines?
provides a 128-MFrame trace memory,
which can record up to 10 seconds of
❏ Are there any cache lines that are
not, or hardly, being used?
program run time.
Cache Analyzer
Cache Analyzer
TRACE32 - Technical Information 7
Figure 6: Analysis of the cache hit/cache miss/cache victim rates fo
instruction cache (IC) and data (DC) caches
Figure 7: Analysis of the cache hit/cache miss/cache victim rates for the
individual cache lines of the instruction cache
Figure 8: List of program addresses competing for cache line 0x15 of the
instruction cache
Cache Analyzer
Cache Analyzer
TRACE32 - Technical Information 8
therefore, eviction will always occur,
Figure 8 in the above analysis shows resulting in cache victims. At the same
that the program instructions at the time, cache line 0x19 is completely
addresses, 0x8150, 0xA150, and unused. By redirecting the address of
0xC150, are competing for the cache one of the competing program instruc-
line 0x15. The above example uses a tions to the end address 0x190, the
cache in which each cache line has two competition can be removed from
locations in the cache (2-way associa- cache line 0x15 and there will be no
tive cache). Three program addresses further cache victims.
are competing for one cache line;
Cache Analyzer
Cache Analyzer
TRACE32 - Technical Information 9
Relationship Between Cache Efficiency and Program
Run Time
As described in the previous section, between program run time and cache
cache analysis is based on the pro- efficiency can be measured and veri-
gram and data flow recorded in the fied using TRACE32-PowerTrace.
trace memory. As all entries in the
trace memory have a time stamp, the Figure 9 shows how the function ana-
trace contents are used as the basis for lyzed has a cache hit rate of 79% and a
run time measurements. This has the cache victim rate of 21% for the cache
advantage that the direct relationship line 0x15.
Figure 9: Graphical analysis of the cache hit/cache victim rates for the cache line
0x15.
The high rate of replacement also
becomes apparent when the function’s
run time is studied. The average run
time of the function (sievebad) is 77.6
us.
Figure 10: Run-time analysis of the sievebad function using
TRACE32-PowerTrace
Cache Analyzer
Cache Analyzer
TRACE32 - Technical Information 10
mized function (sievegood) shows an
By redirecting the address of one of the immediate and considerable improve-
competing program instructions to the ment in run-time performance. The run
end address 0x190, the competition is time is on average only 7.9 us.
removed from cache line 0x15. As only
two addresses are now competing for
this cache line, there is no need for fur-
ther eviction. An analysis of the opti-
Figure 11: Run-time analysis of the sievegood function using
TRACE32-PowerTrace
actually leads to the predicted improve-
Using a combination of cache analysis ment in run times. It can also be used
and run-time measurements, develop- to investigate if code optimizations
ers can use TRACE32-PowerTrace to impair cache efficiency and therefore
test whether optimized cache efficiency do not improve program run times.
Summary
The latest cache analysis tool from required, the predefined cache struc-
Lauterbach Datentechnik GmbH pro- ture of microcontrollers can also be
vides developers of embedded sys- modified. In this way, an alternative
tems with the following benefits: cache structure can be tested to deter-
mine if its use will lead to greater cache
efficiency and therefore shorten pro-
❏ Optimization of program run
gram run times. The result can then be
times
taken into account for future designs.
❏ Reduction in power consumption
of the entire system
Cache analysis can be performed on
all microcontrollers, cache architec-
tures, and cache hierarchies. If
Cache Analyzer
Cache Analyzer
TRACE32 - Technical Information 11
Contact
International Representative
Australia Finland
Embedded Logic Solutions Pty L Nohau
Mr. Ramzi Kattan Mr. Leevi Lehtinen
391 Hume Highway Teknobulevardi 3-5
Bankstown NSW 2200 FI-01531 Vantaa
Phone: ++61 2 9793 9542 Phone: ++358 40 546 1469
FAX: ++61 2 9790 1183 FAX: ++358 9 2517 8101
EMAIL: sales@emlogic.com.au EMAIL: leevi.lehtinen@nohau.se
Austria France
Lauterbach Datentechnik GmbH Logic Instrument
Mr. Norbert Weiss Mr. Stephane Morice
Fichtenstr. 27 BP 116
D-85649 Hofolding 71, route de Saint-Denis
Phone: ++49 8104 8943 183 F-95170 Deuil la Barre
FAX: ++49 8104 8943 170 Phone: ++33 1 342861 70
EMAIL: info_de@lauterbach.com FAX: ++33 1 342800 50
EMAIL: s.morice@logic-instrument.com
Belgium
Tritec Benelux B.V. Germany
Mr. Robbert de Voogt Lauterbach Datentechnik GmbH
Stationspark 550 Mr. Norbert Weiss
NL-3364 DA Sliedrecht Fichtenstr. 27
Phone: ++31 184 41 41 31 D-85649 Hofolding
FAX: ++31 184 42 36 11 Phone: ++49 8104 8943 183
EMAIL: software@tritec.nl FAX: ++49 8104 8943 170
EMAIL: info_de@lauterbach.com
Brazil
ANACOM Software e Hardware Ltd Germany North
Mr. Rodrigo Ferreira Lauterbach Datentechnik GmbH
Rua Nazareth, 807, Bairro Barc Mr. Klaus Hommann
BR-09551-200 Sao Caetano do Sul Leonhardring 5
Phone: 0055 11 3422-4200 D-31319 Sehnde
FAX: 0055 11 3422-4242 Phone: ++49 5138 6185 0
EMAIL: rferreira@anacom.com.br FAX: ++49 5138 6185 3
EMAIL: klaus.hommann@lauterbach.com
Canada
Lauterbach Inc. India
4 Mount Royal Ave. Electro Systems Ass. Pvt. Ltd.
USA-Marlborough, MA 01752 Mr. G. V. Gurunatham
Phone: ++1 508 303 6812 4215 JK Complex First Main Rd.
FAX: ++1 508 303 6813 IND-Bangalore 560 021
EMAIL: info_us@lauterbach.com Phone: ++91 80 23577924
FAX: ++91 80 23475615
China EMAIL: esaindia@vsnl.com
Watertek Inc. Ireland
Mr. Liu Ming
Room 1006, Hai Tai Building Lauterbach Ltd.
No.229,North Si Huan Zhong Rd. Mr. Barry Lock
PRC-Beijing Hai Dian Distr., 100083 11 Basepoint Enterprise Centre
Phone: +86 10 82883933-680 Stroudley Road
FAX: +86 10 82883858 Basingstoke, Hants RG24 8UP
EMAIL: sales@watertek.com Phone: ++44-1256-333-690
FAX: ++44-1256-336-661
Denmark EMAIL: info_uk@lauterbach.com
Nohau Danmark A/S Israel
Mr. Flemming Jensen
Klausdalsbrovej 493 Itec Ltd.
DK-2730 Herlev Mr. Mauri Gottlieb
Phone: ++45 44 52 16 50 P.O.Box 10002
FAX: ++45 44 52 26 55 IL-Tel Aviv 61100
EMAIL: info@nohau.dk Phone: ++972 3 6491202
FAX: ++972 3 6497661
Egypt EMAIL: general@itec.co.il
Wantech Italy
Mr. Nawara
5 Shafik Ghalie St., Suite 2 Lauterbach Srl
Off Pyramids Road, Giza Mr. Maurizio Menegotto
Cairo 12111 Via Enzo Ferrieri 12
Phone: ++20 2 5848020 I-20153 Milano
FAX: ++20 2 5877303 Phone: ++39 02 45490282
EMAIL: sales@wantechnet.com FAX: ++39 02 45490428
EMAIL: info_it@lauterbach.com
Cache Analyzer
Contact
TRACE32 - Technical Information 12
Japan South Korea
Lauterbach Japan, Ltd. MDS Technology Co.,Ltd.
Mr. Kenji Furukawa Mr. Hyunchul Kim
3-9-5 Shinyokohama 15F Kolon Digital Tower Vilant
Kouhoku-ku #222-7, Guro-3dong, Guro-gu
Yokohama-shi, Japan 222-0033 Seoul, 152-848, ROK
Phone: ++81-45-477-4511 Phone: ++82 2 2106 6000
FAX: ++81-45-477-4519 FAX: ++82 2 2106 6004
EMAIL: info@lauterbach.co.jp EMAIL: trace32@mdstec.com
Luxemburg Spain
Tritec Benelux B.V. Captura Electronica,SCCL
Mr. Robbert de Voogt Mr. Juan Martinez
Stationspark 550 c/Albert Einstein s/n
NL-3364 DA Sliedrecht Edificio Forum de la Tecnol.
Phone: ++31 184 41 41 31 E-08042 Barcelona
FAX: ++31 184 42 36 11 Phone: ++34 93 291 76 33
EMAIL: software@tritec.nl FAX: ++34 93 291 76 35
EMAIL: info@captura-el.com
Malaysia
Flash Technology Sweden
Mr. Teo Kian Hock Nohau Elektronik AB
No 61, # 04-15 Kaki Bukit Av 1 Mr.Greger Andersson
Shun Li Industrial Park Derbyvägen 4
SGP-Singapore 417943 SE-21235 Malmoe
Phone: ++65 6749 6168 Phone: ++46 40 59 22 00
FAX: ++65 6749 6138 FAX: ++46 40 59 22 29
EMAIL: flashsgp@pacific.net.sg EMAIL: info@nohau.se
Netherlands Switzerland
Tritec Benelux B.V. JDT Jberg DatenTechnik
Mr. Robbert de Voogt Mr. Andreas Iberg
Stationspark 550 Zimmereistrasse 2
NL-3364 DA Sliedrecht CH-5734 Reinach AG
Phone: ++31 184 41 41 31 Phone: ++41 62 7710 886
FAX: ++31 184 42 36 11 FAX: ++41 62 7717 187
EMAIL: software@tritec.nl EMAIL: Andreas.Jberg@jdt.ch
New Zealand Taiwan
Embedded Logic Solutions Pty L Superlink Technology Corp.
Mr. Ramzi Kattan Mr. Sulin Huang
391 Hume Highway 3F-8,No.77,Shin-Tai-Wu Rd.Sec1
Bankstown NSW 2200 Taipei Hsien 221, Taiwan, R.O.C.
Phone: ++61 2 9793 9542 Phone: ++886 2 26983456
FAX: ++61 2 9790 1183 FAX: ++886 2 26983535
EMAIL: sales@emlogic.com.au EMAIL: stc@tpts1.seed.net.tw
Norway Turkey
Nohau Elektronik AB Bildem Bilgisayar Ltd. Sti.
Mr. Greger Andersson Mr. Hakan Yavuz
Derbyvägen 4 Koroglu Cad. 64/3 G.O.Pasa
S-21235 Malmoe TR-06700 Ankara
Phone: ++46 40 59 22 00 Phone: ++90 312 4472700
FAX: ++46 40 59 22 29 FAX: ++90 312 4472702
EMAIL: info@nohau.se EMAIL: info@bildem.com.tr
Poland UK
Quantum Sp.z o.o. Korp. Transf Lauterbach Ltd.
Mr. Czeslaw Bil Mr. Barry Lock
ul. Skwierzynska 21 11 Basepoint Enterprise Centre
53-521 Wroclaw Stroudley Rd
Phone: ++48 71 362 6356 Basingstoke, Hants RG24 8UP
FAX: ++48 71 362 6357 Phone: ++44 (0) 1256-333690
EMAIL: bil@quantum.com.pl FAX: ++44 (0) 1256-336661
EMAIL: info_uk@lauterbach.com
Portugal
Captura Electronica,SCCL USA East
Mr. Juan Martinez Lauterbach Inc.
c/Albert Einstein s/n Mr. Udo Zoettler
Edificio Forum de la Tecnol. 4 Mount Royal Ave.
E-08042 Barcelona USA-Marlborough, MA 01752
Phone: ++34 93 291 76 33 Phone: ++1 508 303 6812
FAX: ++34 93 291 76 35 FAX: ++1 508 303 6813
EMAIL: info@captura-el.com EMAIL: info_us@lauterbach.com
Singapore USA West
Flash Technology Lauterbach Inc.
Mr. Teo Kian Hock Mr. Jerry Flake
No 61, # 04-15 Kaki Bukit Av 1 13256 SW. Hillshire Drive
Shun Li Industrial Park USA-Tigard, OR 97223
SGP-Singapore 417943 Phone: ++1 503 524 2222
Phone: ++65 6749 6168 FAX: (503) 524 2223
FAX: ++65 6749 6138 EMAIL: jerry.flake@lauterbach.com
EMAIL: flashsgp@pacific.net.sg
Cache Analyzer
Contact
TRACE32 - Technical Information 13
Additional Information
http://www.lauterbach.com
Lauterbach Datentechnik GmbH Lauterbach Japan, Ltd.
Fichtenstr. 27 3-9-5 Shinyokohama Kouhoku-ku
D-85649 Hofolding Yokohama-shi Japan 222-0033
Tel. ++49 8104 8943-188 FAX -187 Phone ++81-45-477-4511 FAX -4519
info@lauterbach.com info_j@lauterbach.com
http://www.lauterbach.de http://www.lauterbach.co.jp
Lauterbach Inc. Lauterbach s.r.l.
4 Mount Royal Ave. Lauterbach s.r.l.
Marlboro MA 01752 Via Enzo Ferrieri 12
Phone (508) 303 6812 FAX (508) 303 6813 I-20153 Milano
info_us@lauterbach.com Phone ++39 02 45490282
http://www.lauterbach.com/usa FAX ++39 02 45490428
info_it@lauterbach.it
Lauterbach Ltd. http://www.lauterbach.it
11 Basepoint Enterprise Ctre Stroudley Road
Basingstoke, Hants RG24 8UP
Phone ++44-1256-333-690 FAX -661
info_uk@lauterbach.com
http:/www.lauterbach.co.uk
Disclaimer
The information presented is intended to give overview information only.
Changes and technical enhancements or modifications can be made with-
Cache Analyzer
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