This patchset is based on Juan Quintela's old series here https://lore.kernel.org/all/20220802063907.18882-1-quint...@redhat.com/
In the multifd live migration model, there is a single migration main thread scanning the page map, queuing the pages to multiple multifd sender threads. The migration main thread runs zero page checking on every page before queuing the page to the sender threads. Zero page checking is a CPU intensive task and hence having a single thread doing all that doesn't scale well. This change introduces a new function to run the zero page checking on the multifd sender threads. This patchset also lays the ground work for future changes to offload zero page checking task to accelerator hardwares. Use two Intel 4th generation Xeon servers for testing. Architecture: x86_64 CPU(s): 192 Thread(s) per core: 2 Core(s) per socket: 48 Socket(s): 2 NUMA node(s): 2 Vendor ID: GenuineIntel CPU family: 6 Model: 143 Model name: Intel(R) Xeon(R) Platinum 8457C Stepping: 8 CPU MHz: 2538.624 CPU max MHz: 3800.0000 CPU min MHz: 800.0000 Perform multifd live migration with below setup: 1. VM has 100GB memory. All pages in the VM are zero pages. 2. Use tcp socket for live migratio. 3. Use 4 multifd channels and zero page checking on migration main thread. 4. Use 1/2/4 multifd channels and zero page checking on multifd sender threads. 5. Record migration total time from sender QEMU console's "info migrate" command. 6. Calculate throughput with "100GB / total time". +------------------------------------------------------+ |zero-page-checking | total-time(ms) | throughput(GB/s)| +------------------------------------------------------+ |main-thread | 9629 | 10.38GB/s | +------------------------------------------------------+ |multifd-1-threads | 6182 | 16.17GB/s | +------------------------------------------------------+ |multifd-2-threads | 4643 | 21.53GB/s | +------------------------------------------------------+ |multifd-4-threads | 4143 | 24.13GB/s | +------------------------------------------------------+ Apply this patchset on top of commit 39a6e4f87e7b75a45b08d6dc8b8b7c2954c87440 Hao Xiang (6): migration/multifd: Add new migration option multifd-zero-page. migration/multifd: Add zero pages and zero bytes counter to migration status interface. migration/multifd: Support for zero pages transmission in multifd format. migration/multifd: Zero page transmission on the multifd thread. migration/multifd: Enable zero page checking from multifd threads. migration/multifd: Add a new migration test case for legacy zero page checking. migration/migration-hmp-cmds.c | 11 ++++ migration/multifd.c | 106 ++++++++++++++++++++++++++++----- migration/multifd.h | 22 ++++++- migration/options.c | 20 +++++++ migration/options.h | 1 + migration/ram.c | 49 ++++++++++++--- migration/trace-events | 8 +-- qapi/migration.json | 39 ++++++++++-- tests/qtest/migration-test.c | 26 ++++++++ 9 files changed, 249 insertions(+), 33 deletions(-) -- 2.30.2