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docs: Update guestfs-performance with parallel scaling numbers and test script.

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Richard W.M. Jones
2013-02-23 22:35:48 +00:00
parent ff80a54011
commit 680450f3b4
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examples/guestfs-performance.pod
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@@ -267,6 +267,107 @@ Linux but expensive on Windows.
=back
=head1 PARALLEL APPLIANCES
Libguestfs appliances are mostly I/O bound and you can launch multiple
appliances in parallel. Provided there is enough free memory, there
should be little difference in launching 1 appliance vs N appliances
in parallel.
On a 2-core (4-thread) laptop with 16 GB of RAM, using the (not
especially realistic) test Perl script below, the following plot shows
excellent scalability when running between 1 and 20 appliances in
parallel:
12 ++---+----+----+----+-----+----+----+----+----+---++
+ + + + + + + + + + *
| |
| * |
11 ++ ++
| |
| |
| * * |
10 ++ ++
| * |
| |
s | |
9 ++ ++
e | |
| * |
c | |
8 ++ * ++
o | * |
| |
n 7 ++ ++
| * |
d | * |
| |
s 6 ++ ++
| * * |
| * |
| |
5 ++ ++
| |
| * |
| * * |
4 ++ ++
| |
| |
+ * * * + + + + + + + +
3 ++-*-+----+----+----+-----+----+----+----+----+---++
0 2 4 6 8 10 12 14 16 18 20
number of parallel appliances
It is possible to run many more than 20 appliances in parallel, but if
you are using the libvirt backend then you should be aware that out of
the box libvirt limits the number of client connections to 20.
The simple Perl script below was used to collect the data for the plot
above, but there is much more information on this subject, including
more advanced test scripts and graphs, available in the following blog
postings:
L<http://rwmj.wordpress.com/2013/02/25/multiple-libguestfs-appliances-in-parallel-part-1/>
L<http://rwmj.wordpress.com/2013/02/25/multiple-libguestfs-appliances-in-parallel-part-2/>
L<http://rwmj.wordpress.com/2013/02/25/multiple-libguestfs-appliances-in-parallel-part-3/>
L<http://rwmj.wordpress.com/2013/02/25/multiple-libguestfs-appliances-in-parallel-part-4/>
#!/usr/bin/perl -w
use strict;
use threads;
use Sys::Guestfs;
use Time::HiRes qw(time);
sub test {
my $g = Sys::Guestfs->new;
$g->add_drive_ro ("/dev/null");
$g->launch ();
# You could add some work for libguestfs to do here.
$g->close ();
}
# Get everything into cache.
test (); test (); test ();
for my $nr_threads (1..20) {
my $start_t = time ();
my @threads;
foreach (1..$nr_threads) {
push @threads, threads->create (\&test)
}
foreach (@threads) {
$_->join ();
if (my $err = $_->error ()) {
die "launch failed with $nr_threads threads: $err"
}
}
my $end_t = time ();
printf ("%d %.2f\n", $nr_threads, $end_t - $start_t);
}
=head1 TROUBLESHOOTING POOR PERFORMANCE
=head2 ENSURE HARDWARE VIRTUALIZATION IS AVAILABLE