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/* Copyright (c) 2010-2025. The SimGrid Team. All rights reserved. */
/* This program is free software; you can redistribute it and/or modify it
* under the terms of the license (GNU LGPL) which comes with this package. */
import org.simgrid.s4u.*;
class Writer extends Actor {
public void run()
{
/* - Retrieve all disks from current host */
Disk[] disk_list = Host.current().get_disks();
/* - Write 4,000,000 bytes on Disk1 */
disk_list[0].write(4000000);
Engine.info("First write done.");
/* - Write 4,000,000 bytes on Disk1 again */
disk_list[0].write(4000000);
Engine.info("Second write done.");
}
}
class PrivilegedWriter extends Actor {
public void run() throws TimeoutException
{
/* - Retrieve all disks from current host */
Disk[] disk_list = Host.current().get_disks();
/* - Write 4,000,000 bytes on Disk1 but specifies that this I/O operation gets a larger share of the resource.
*
* Since the priority is 2, it writes twice as fast as a regular one.
*
* So instead of a half/half sharing between the two, we get a 1/3 vs. 2/3 sharing. */
disk_list[0].write(4000000, 2);
Engine.info("First write done.");
/* Note that the timings printed when running this example are a bit misleading, because the uneven sharing only
* last until the privileged actor ends. After this point, the unprivileged one gets 100% of the disk and finishes
* quite quickly. */
/* Resynchronize actors before second write */
this.sleep_for(0.05);
/* - Write 4,000,000 bytes on Disk1 again and this time :
* - Start the I/O operation asynchronously to get an IoPtr
* - Let the actor sleep while half of the data is written
* - Double its priority
* - Wait for the end of the I/O operation
*
* Writing the second half of the data with a higher priority, and thus 2/3 of the bandwidth takes 0.075s.
* In the meantime, the regular writer has only 1/3 of the bandwidth and thus only writes 1MB. After the
* completion of the I/O initiated by the privileged writer, the regular writer has the full bandwidth available and
* only needs 0.025s to write the last MB.
*/
Io io = disk_list[0].write_async(4000000);
this.sleep_for(0.1);
Engine.info("Increase priority for the priviledged writer (%.0f bytes remaining to write)", io.get_remaining());
io.update_priority(2);
io.await();
Engine.info("Second write done.");
}
}
public class io_priority {
public static void main(String[] args)
{
Engine e = new Engine(args);
e.load_platform(args[0]);
e.host_by_name("bob").add_actor("writer", new Writer());
e.host_by_name("bob").add_actor("privileged_writer", new PrivilegedWriter());
e.run();
// The following call is useless in your code, but our continuous integration uses it to track memleaks
e.force_garbage_collection();
}
}
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