IDGF
International Desktop Grid Federation
ASSESSING THE PERFORMANCE OF
DESKTOP GRID APPLICATIONS
A. Afanasiev, N. Khrapov, and M. Posypkin
DEGISCO is supported by the FP7 Capacities Programme under contract nr RI-261561.
1
Desktop Grids in a Few Words
“Desktop Grids, Desktop Clouds, allow to employ otherwise
idle computing time of Desktop computers for large
computational programmes. Desktop Grids can be used
inside an organisation, or they can collect computing time
from volunteers all over the country, or even all over the
world.” (IDGF Flyer)
2
Why Understanding the
Performance is Important?
 Desktop Grids collect huge number (millions)
of CPUs
 But there are huge overheads:
– nodes are not available all the time
– only a part of CPU power is available
– high percentage of faults
– heterogeneity
 The real performance is much less than the
peak one
DEGISCO WP4 31/07/2017
3
3
Why Understanding the
Performance is Important?
 Know what you really gain from
parallelization
 Identify sources of overhead
 Compare different load distribution policies
and select the best
DEGISCO WP4 31/07/2017
4
4
The “Parallel” Speedup
The speedup is defined as the ratio of the time taken to
solve a problem on a single processing element to the
time required to solve the same problem on a parallel
computer with p identical processing elements.
(Ananth Grama, Anshul Gupta, George Karypis, Vipin Kumar, Introduction
to Parallel Computing, Addison-Wesley, 2003.)
Ts
Sp 
Tp
DEGISCO WP4 31/07/2017
5
5
The “Parallel” Speedup
Doesn’t work for desktop-grid systems because of two
reasons:
1. Desktop Grid applications are long running (weeks,
months) => Ts is too large to obtain in a reasonable
time
2. The processors are NOT identical => which
processor should be used as a reference?
DEGISCO WP4 31/07/2017
6
6
Desktop Grid Terminology
Results
Workunits
7
Speedup Notion for Desktop Grids
Speedup
Ttot
Sd 
Ms
Total time (sum for all successful T 
tot
workunits)
Makespan
 t ( x)
xU
Ms  t stop  t start
For parallel systems Ttot  Ts , Ms  T p
and thus
Sd  S p
8
The Speedup as a Function of Time Interval
The introduced notion of speedup requires the application to
terminate – not very practical for long running tasks. We can
define the speedup for a given time interval:
Ttot (t1 , t 2 )
S d (t1 , t 2 ) 
t 2  t1
Ttot (t1 , t2 ) a total time of a useful job performed between
moments t1 and t2.
9
How to compute Ttot(t1,t2)?
accounted
internal jobs
external jobs
boundary jobs
t2
t1
Boundary jobs are not accounted but
contribute to the useful job!
err 
10
N boundary
N internal
not
accounted
How to compute Ttot(t1,t2)?
For accurate
measurement we
need:
err 
t2
t1
N boundary
N internal
N boundary  N internal
tav  t2  t1
11
1
Replication
Results
Workunits
12
What to do with Replication?
Replication is used in Desktop Grids to
guarantee the result correctness and to
achieve better load balancing
1 r
t ( x )   t ( xr )
r i 1
We take average time over all successful
replicas
13
Implementation
BOINC
periodic task
Logger
Web-based
UI
Log files
14
Based on Google
Web Toolkit
Implementation
15
Application to OPTIMA@home


The performance evaluation tools have been
deployed at OPTIMA@home project (available
through administrative Web-interface)
Helped to measure the real speedup and to compare
the efficiency of different load distribution strategies
DEGISCO WP4 31/07/2017
16
16
Other Tools: SZTAKI Package
Good tool
shipped with
the SZTAKI
Desktop Grid:
shows the
performance
of your project
in GFlops
17
Other Tools: Statistic Sites
BOINCStats calculates the average performance
DEGISCO WP4 31/07/2017
18
18
The Comparison
 Speedup is more informative than GFlops
performance
 Speedup is application oriented while the
performance is infrastructure-oriented
 The user should have a possibility to tune the
time interval
 It is good to know both speedup and
performance
DEGISCO WP4 31/07/2017
19
19
Conclusions and Future Work
 Extend the notion of parallel efficiency in a
similar way
 Improve web-interface
 Make our tools publically available open
source
 Maybe integrate with some existing package
e.g. SZTAKI desktop grid
DEGISCO WP4 31/07/2017
20
20
IDGF
International Desktop Grid Federation
http://desktopgridfederation.org/
Globe adapted from
http://upload.wikimedia.org/
wikipedia/commons/f/fa/
Globe.svg
21