Hamza Kaya wrote:
Hi Murali,
I found these functions from a previous post in this mail list [pvfs2
native api]. I will attach the code too. As you guess they use the
system interface to handle file operations.
Yeah, we don't support that code. Use at your own risk :).
I used the unix calls (fopen etc.) instead of the pvfs_* calls. It works
correctly.
Another thing I tried is to use fork() instead of pthreads. The pseudo
code is as follows:
main:
for 1 to n
{
fork ();
child {
PVFS_util_init_defaults ();
thread_func ();
PVFS_sys_finalize ();
}
}
parent {
waitforchilds;
}
thread_func:
filesize=1GB
offset= rand (0 - 1GB)
for i to m
{
PVFS_sys_read (100KB, offset);
}
this code works correctly.
When I used fork and unix calls I got approximately 3 thread_func calls
per second. However with fork and system interface I got approx. 400
thread_func calls per second. What may cause this difference? In the
first case I observed that the client machine and the server machine
contacts with the same port number. In other words client use the same
port number to connect the servers 3334th port. In the second case this
port number changed. I observed many different port numbers connecting
to pvfs2 servers port. [Raw sockets used to listen the network] May be
the reason is this.
The pvfs2-client uses a single TCP connection to communicate with the
server. Multiple processes started in the way you describe will use
multiple connections (because they have no way to share a single one).
That might be one reason for the difference in performance -- with only
one connection to the server, there is more potential for serialization.
Given the errors that you're getting, it's quite possible that the
system interface version just isn't working right. Have you checked to
see if you are getting correct results?
We haven't spent a lot of time tweaking multiprocess per node
performance, yet.
Thanks,
Rob
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