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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. */
#include "simgrid/s4u.hpp"
XBT_LOG_NEW_DEFAULT_CATEGORY(s4u_test, "Messages specific for this s4u example");
namespace sg4 = simgrid::s4u;
static void writer()
{
/* - Retrieve all disks from current host */
std::vector<sg4::Disk*> const& disk_list = sg4::Host::current()->get_disks();
/* - Write 4,000,000 bytes on Disk1 */
disk_list.front()->write(4000000);
XBT_INFO("First write done.");
/* - Write 4,000,000 bytes on Disk1 again */
disk_list.front()->write(4000000);
XBT_INFO("Second write done.");
}
static void privileged_writer()
{
/* - Retrieve all disks from current host */
std::vector<sg4::Disk*> const& disk_list = sg4::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.front()->write(4000000, 2);
XBT_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 */
sg4::this_actor::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.
*/
sg4::IoPtr io = disk_list.front()->write_async(4000000);
sg4::this_actor::sleep_for(0.1);
XBT_INFO("Increase priority for the priviledged writer (%.0f bytes remaining to write)", io->get_remaining());
io->update_priority(2);
io->wait();
XBT_INFO("Second write done.");
}
int main(int argc, char* argv[])
{
sg4::Engine e(&argc, argv);
xbt_assert(argc > 1, "Usage: %s platform_file\n\tExample: %s platform.xml\n", argv[0], argv[0]);
e.load_platform(argv[1]);
e.add_actor("writer", e.host_by_name("bob"), writer);
e.add_actor("privileged_writer", e.host_by_name("bob"), privileged_writer);
e.run();
return 0;
}
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