This series does many of the improvements that the migration thread
promised. First, it simplifies substantially the logic of the migration
thread, which makes it easier to do more changes later (patches 1-14).
Second, It makes a large amount of code run outside the big QEMU
lock, so that blocking writes will not starve other threads seeking
to grab the big QEMU mutex---and this in turn lets us remove buffering
(patches 15-24).
Third, it completes the cleanup of rate limiting, which lets us removes
some duplication between incoming and outgoing migration and use QEMUFile
in a much simpler way (patches 25-42).
While my main purpose here is to move the code in the "right" direction,
the saner locking and removed copies give a nice performance bump.
On trivial workloads (idle guests), having little or no iothread lock
contention already improves performance by ~5%. In real-world scenarios,
however, QEMU can now achieve 2.5-3 Gbps on a 10G link, compared to
1.5-1.8 before these patches. Jitter is also improved nicely, though
the previous work on the migration thread already had some effect there.
Much to my surprise, block migration is still working nicely, with no
contortions and only a minimal amount of code running under the iothread
lock. You probably won't here me talking anymore about deprecating it.
Let it rot^Wrest in peace.
Thanks Juan and Orit for the quick review.
v1->v2:
rebased; made changes suggested by Juan and Orit; integrated
Kazuya Saito's migrate_set_state tracepoint; added
WIFEXITED/WEXITSTATUS defines for Windows; minor checkpatch
complaints.
Juan Quintela (1):
Rename buffered_ to migration_
Kazuya Saito (1):
migration: add migrate_set_state tracepoint
Paolo Bonzini (40):
migration: simplify while loop
migration: always use vm_stop_force_state
migration: move more error handling to migrate_fd_cleanup
migration: push qemu_savevm_state_cancel out of qemu_savevm_state_*
block-migration: remove useless calls to blk_mig_cleanup
qemu-file: pass errno from qemu_fflush via f->last_error
migration: use qemu_file_set_error to pass error codes back to
qemu_savevm_state
qemu-file: temporarily expose qemu_file_set_error and qemu_fflush
migration: flush all data to fd when buffered_flush is called
migration: use qemu_file_set_error
migration: simplify error handling
migration: do not nest flushing of device data
migration: prepare to access s->state outside critical sections
migration: cleanup migration (including thread) in the iothread
block-migration: remove variables that are never read
block-migration: small preparatory changes for locking
block-migration: document usage of state across threads
block-migration: add lock
migration: reorder SaveVMHandlers members
migration: run pending/iterate callbacks out of big lock
migration: run setup callbacks out of big lock
migration: yay, buffering is gone
qemu-file: make qemu_fflush and qemu_file_set_error private again
migration: eliminate last_round
migration: detect error before sleeping
migration: remove useless qemu_file_get_error check
migration: use qemu_file_rate_limit consistently
migration: merge qemu_popen_cmd with qemu_popen
qemu-file: fsync a writable stdio QEMUFile
qemu-file: check exit status when closing a pipe QEMUFile
qemu-file: add writable socket QEMUFile
qemu-file: simplify and export qemu_ftell
migration: use QEMUFile for migration channel lifetime
migration: use QEMUFile for writing outgoing migration data
migration: use qemu_ftell to compute bandwidth
migration: small changes around rate-limiting
migration: move rate limiting to QEMUFile
migration: move contents of migration_close to migrate_fd_cleanup
migration: eliminate s->migration_file
migration: inline migrate_fd_close
arch_init.c | 14 +-
block-migration.c | 167 ++++++++++++++------
docs/migration.txt | 20 +--
include/migration/migration.h | 12 +-
include/migration/qemu-file.h | 21 +--
include/migration/vmstate.h | 21 ++-
include/qemu/atomic.h | 1 +
include/qemu/osdep.h | 7 +
include/sysemu/sysemu.h | 6 +-
migration-exec.c | 39 +----
migration-fd.c | 47 +-----
migration-tcp.c | 33 +---
migration-unix.c | 33 +---
migration.c | 357 ++++++++++--------------------------------
savevm.c | 214 ++++++++++++++-----------
trace-events | 3 +
16 files changed, 385 insertions(+), 610 deletions(-)
--
1.8.1.2
