Thank you all for the comments in the previous version. I believe we managed to remove much of the complexity of the fdset handling.
Major changes in this v2 are: - The rework of fdset to be less weird when removing fds. Now we always remove after qmp_remove_fd() and never remove after the monitor closes. Also removed the ->removed flag. - Properly check for direct-io during params_check. I'm not going with the meson.build approach because that's kind of novel for migration paramters and I don't want to make direct-io a special case. I also couldn't figure out a way of selecting on CONFIG_O_DIRECT that would not end up removing the direct_io fields from everywhere, forcing us to check the CONFIG all over the place. New in this v2 are two options to make the usage of the feature more uniform and require less special cases in the management layer: - Precopy direct-io. When not using multifd, enable and disable O_DIRECT around the parts of the code known to be aligned. - Implemented direct-io for the incoming side. CI run: https://gitlab.com/farosas/qemu/-/pipelines/1302882857 v1: https://lore.kernel.org/r/20240426142042.14573-1-faro...@suse.de Hi everyone, here's the rest of the migration "mapped-ram" feature that didn't get merged for 9.0. This series adds support for direct I/O, the missing piece to get the desired performance improvements. There's 3 parts to this: 1- The plumbing for the new "direct-io" migration parameter. With this we can already use direct-io with the file transport + multifd + mapped-ram. Patches 1-3. Due to the alignment requirements of O_DIRECT and the fact that multifd runs the channels in parallel with the migration thread, we must open the migration file two times, one with O_DIRECT set and another with it clear. If the user is not passing in a file name which QEMU can open at will, we must then require that the user pass the two file descriptors with the flags already properly set. We'll use the already existing fdset + QMP add-fd infrastructure for this. 2- Changes to the fdset infrastructure to support O_DIRECT. We need those to be able to select from the user-provided fdset the file descriptor that contains the O_DIRECT flag. Patches 4-5. 3- Some fdset validation to make sure the two-fds requirement is being met. Patches 6-7. CI run: https://gitlab.com/farosas/qemu/-/pipelines/1269352083 Fabiano Rosas (17): migration: Fix file migration with fdset tests/qtest/migration: Fix file migration offset check tests/qtest/migration: Add a precopy file test with fdset monitor: Introduce monitor_fdset_*free monitor: Stop removing non-duplicated fds monitor: Simplify fdset and fd removal monitor: Report errors from monitor_fdset_dup_fd_add io: Stop using qemu_open_old in channel-file migration: Add direct-io parameter migration/multifd: Add direct-io support tests/qtest/migration: Add tests for file migration with direct-io monitor: fdset: Match against O_DIRECT migration: Add documentation for fdset with multifd + file tests/qtest/migration: Add a test for mapped-ram with passing of fds io/channel-file: Add direct-io support migration: Add direct-io helpers migration/ram: Add direct-io support to precopy file migration Peter Xu (1): monitor: Drop monitor_fdset_dup_fd_add() docs/devel/migration/main.rst | 24 ++- docs/devel/migration/mapped-ram.rst | 6 +- include/io/channel-file.h | 8 + include/monitor/monitor.h | 3 +- include/qemu/osdep.h | 2 + io/channel-file.c | 33 +++- migration/file.c | 42 +++- migration/file.h | 1 - migration/migration-hmp-cmds.c | 11 ++ migration/migration.c | 54 +++++ migration/migration.h | 2 + migration/options.c | 28 +++ migration/options.h | 1 + migration/qemu-file.c | 29 +++ migration/qemu-file.h | 2 +- migration/ram.c | 40 +++- monitor/fds.c | 89 ++++----- monitor/hmp.c | 2 - monitor/monitor-internal.h | 1 - monitor/qmp.c | 2 - qapi/migration.json | 21 +- stubs/fdset.c | 7 +- tests/qtest/migration-helpers.c | 44 +++++ tests/qtest/migration-helpers.h | 8 + tests/qtest/migration-test.c | 296 +++++++++++++++++++++++++--- util/osdep.c | 34 ++-- 26 files changed, 652 insertions(+), 138 deletions(-) base-commit: 7e1c0047015ffbd408e1aa4a5ec1abe4751dbf7e -- 2.35.3
