1 /* Copyright (c) 2010-2021. The SimGrid Team. All rights reserved. */
3 /* This program is free software; you can redistribute it and/or modify it
4 * under the terms of the license (GNU LGPL) which comes with this package. */
6 #include "simgrid/s4u.hpp"
8 XBT_LOG_NEW_DEFAULT_CATEGORY(s4u_test, "Messages specific for this s4u example");
12 /* - Retrieve all disks from current host */
13 std::vector<simgrid::s4u::Disk*> const& disk_list = simgrid::s4u::Host::current()->get_disks();
14 /* - Write 4,000,000 bytes on Disk1 */
15 disk_list.front()->write(4000000);
16 XBT_INFO("First write done.");
17 /* - Write 4,000,000 bytes on Disk1 again */
18 disk_list.front()->write(4000000);
19 XBT_INFO("Second write done.");
22 static void privileged_writer()
24 /* - Retrieve all disks from current host */
25 std::vector<simgrid::s4u::Disk*> const& disk_list = simgrid::s4u::Host::current()->get_disks();
27 /* - Write 4,000,000 bytes on Disk1 but specifies that this I/O operation gets a larger share of the resource.
29 * Since the priority is 2, it writes twice as fast as a regular one.
31 * So instead of a half/half sharing between the two, we get a 1/3 vs. 2/3 sharing. */
32 disk_list.front()->io_init(4000000, simgrid::s4u::Io::OpType::WRITE)->set_priority(2)->wait();
33 XBT_INFO("First write done.");
35 /* Note that the timings printed when running this example are a bit misleading, because the uneven sharing only last
36 * until the privileged actor ends. After this point, the unprivileged one gets 100% of the disk and finishes quite
39 /* Resynchronize actors before second write */
40 simgrid::s4u::this_actor::sleep_for(0.05);
42 /* - Write 4,000,000 bytes on Disk1 again and this time :
43 * - Start the I/O operation asynchronously to get an IoPtr
44 * - Let the actor sleep while half of the data is written
45 * - Double its priority
46 * - Wait for the end of the I/O operation
48 * Writing the second half of the data with a higher priority, and thus 2/3 of the bandwidth takes 0.075s.
49 * In the meantime, the regular writer has only 1/3 of the bandwidth and thus only writes 1MB. After the completion
50 * of the I/O initiated by the privileged writer, the regular writer has the full bandwidth available and only needs
51 * 0.025s to write the last MB.
54 simgrid::s4u::IoPtr io = disk_list.front()->write_async(4000000);
55 simgrid::s4u::this_actor::sleep_for(0.1);
56 XBT_INFO("Increase priority for the priviledged writer (%.0f bytes remaining to write)", io->get_remaining());
57 io->update_priority(2);
59 XBT_INFO("Second write done.");
62 int main(int argc, char* argv[])
64 simgrid::s4u::Engine e(&argc, argv);
65 xbt_assert(argc > 1, "Usage: %s platform_file\n\tExample: %s platform.xml\n", argv[0], argv[0]);
67 e.load_platform(argv[1]);
69 simgrid::s4u::Actor::create("writer", e.host_by_name("bob"), writer);
70 simgrid::s4u::Actor::create("privileged_writer", e.host_by_name("bob"), privileged_writer);