On Tue, Nov 19, 2024 at 1:31 PM Fabiano Rosas <faro...@suse.de> wrote: > > Yichen Wang <yichen.w...@bytedance.com> writes: > > > v7 > > * Rebase on top of f0a5a31c33a8109061c2493e475c8a2f4d022432; > > * Fix a bug that will crash QEMU when DSA initialization failed; > > * Use a more generalized accel-path to support other accelerators; > > * Remove multifd-packet-size in the parameter list; > > > > v6 > > * Rebase on top of 838fc0a8769d7cc6edfe50451ba4e3368395f5c1; > > * Refactor code to have clean history on all commits; > > * Add comments on DSA specific defines about how the value is picked; > > * Address all comments from v5 reviews about api defines, questions, etc.; > > > > v5 > > * Rebase on top of 39a032cea23e522268519d89bb738974bc43b6f6. > > * Rename struct definitions with typedef and CamelCase names; > > * Add build and runtime checks about DSA accelerator; > > * Address all comments from v4 reviews about typos, licenses, comments, > > error reporting, etc. > > > > v4 > > * Rebase on top of 85b597413d4370cb168f711192eaef2eb70535ac. > > * A separate "multifd zero page checking" patchset was split from this > > patchset's v3 and got merged into master. v4 re-applied the rest of all > > commits on top of that patchset, re-factored and re-tested. > > https://lore.kernel.org/all/20240311180015.3359271-1-hao.xi...@linux.dev/ > > * There are some feedback from v3 I likely overlooked. > > > > v3 > > * Rebase on top of 7425b6277f12e82952cede1f531bfc689bf77fb1. > > * Fix error/warning from checkpatch.pl > > * Fix use-after-free bug when multifd-dsa-accel option is not set. > > * Handle error from dsa_init and correctly propogate the error. > > * Remove unnecessary call to dsa_stop. > > * Detect availability of DSA feature at compile time. > > * Implement a generic batch_task structure and a DSA specific one > > dsa_batch_task. > > * Remove all exit() calls and propagate errors correctly. > > * Use bytes instead of page count to configure multifd-packet-size option. > > > > v2 > > * Rebase on top of 3e01f1147a16ca566694b97eafc941d62fa1e8d8. > > * Leave Juan's changes in their original form instead of squashing them. > > * Add a new commit to refactor the multifd_send_thread function to prepare > > for introducing the DSA offload functionality. > > * Use page count to configure multifd-packet-size option. > > * Don't use the FLAKY flag in DSA tests. > > * Test if DSA integration test is setup correctly and skip the test if > > * not. > > * Fixed broken link in the previous patch cover. > > > > * Background: > > > > I posted an RFC about DSA offloading in QEMU: > > https://patchew.org/QEMU/20230529182001.2232069-1-hao.xi...@bytedance.com/ > > > > This patchset implements the DSA offloading on zero page checking in > > multifd live migration code path. > > > > * Overview: > > > > Intel Data Streaming Accelerator(DSA) is introduced in Intel's 4th > > generation > > Xeon server, aka Sapphire Rapids. > > https://cdrdv2-public.intel.com/671116/341204-intel-data-streaming-accelerator-spec.pdf > > https://www.intel.com/content/www/us/en/content-details/759709/intel-data-streaming-accelerator-user-guide.html > > One of the things DSA can do is to offload memory comparison workload from > > CPU to DSA accelerator hardware. This patchset implements a solution to > > offload > > QEMU's zero page checking from CPU to DSA accelerator hardware. We gain > > two benefits from this change: > > 1. Reduces CPU usage in multifd live migration workflow across all use > > cases. > > 2. Reduces migration total time in some use cases. > > > > * Design: > > > > These are the logical steps to perform DSA offloading: > > 1. Configure DSA accelerators and create user space openable DSA work > > queues via the idxd driver. > > 2. Map DSA's work queue into a user space address space. > > 3. Fill an in-memory task descriptor to describe the memory operation. > > 4. Use dedicated CPU instruction _enqcmd to queue a task descriptor to > > the work queue. > > 5. Pull the task descriptor's completion status field until the task > > completes. > > 6. Check return status. > > > > The memory operation is now totally done by the accelerator hardware but > > the new workflow introduces overheads. The overhead is the extra cost CPU > > prepares and submits the task descriptors and the extra cost CPU pulls for > > completion. The design is around minimizing these two overheads. > > > > 1. In order to reduce the overhead on task preparation and submission, > > we use batch descriptors. A batch descriptor will contain N individual > > zero page checking tasks where the default N is 128 (default packet size > > / page size) and we can increase N by setting the packet size via a new > > migration option. > > 2. The multifd sender threads prepares and submits batch tasks to DSA > > hardware and it waits on a synchronization object for task completion. > > Whenever a DSA task is submitted, the task structure is added to a > > thread safe queue. It's safe to have multiple multifd sender threads to > > submit tasks concurrently. > > 3. Multiple DSA hardware devices can be used. During multifd initialization, > > every sender thread will be assigned a DSA device to work with. We > > use a round-robin scheme to evenly distribute the work across all used > > DSA devices. > > 4. Use a dedicated thread dsa_completion to perform busy pulling for all > > DSA task completions. The thread keeps dequeuing DSA tasks from the > > thread safe queue. The thread blocks when there is no outstanding DSA > > task. When pulling for completion of a DSA task, the thread uses CPU > > instruction _mm_pause between the iterations of a busy loop to save some > > CPU power as well as optimizing core resources for the other hypercore. > > 5. DSA accelerator can encounter errors. The most popular error is a > > page fault. We have tested using devices to handle page faults but > > performance is bad. Right now, if DSA hits a page fault, we fallback to > > use CPU to complete the rest of the work. The CPU fallback is done in > > the multifd sender thread. > > 6. Added a new migration option multifd-dsa-accel to set the DSA device > > path. If set, the multifd workflow will leverage the DSA devices for > > offloading. > > 7. Added a new migration option multifd-normal-page-ratio to make > > multifd live migration easier to test. Setting a normal page ratio will > > make live migration recognize a zero page as a normal page and send > > the entire payload over the network. If we want to send a large network > > payload and analyze throughput, this option is useful. > > 8. Added a new migration option multifd-packet-size. This can increase > > the number of pages being zero page checked and sent over the network. > > The extra synchronization between the sender threads and the dsa > > completion thread is an overhead. Using a large packet size can reduce > > that overhead. > > > > * Performance: > > > > We 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 > > > > We perform multifd live migration with below setup: > > 1. VM has 100GB memory. > > 2. Use the new migration option multifd-set-normal-page-ratio to control > > the total > > size of the payload sent over the network. > > 3. Use 8 multifd channels. > > 4. Use tcp for live migration. > > 4. Use CPU to perform zero page checking as the baseline. > > 5. Use one DSA device to offload zero page checking to compare with the > > baseline. > > 6. Use "perf sched record" and "perf sched timehist" to analyze CPU usage. > > > > A) Scenario 1: 50% (50GB) normal pages on an 100GB vm. > > > > CPU usage > > > > |---------------|---------------|---------------|---------------| > > | |comm |runtime(msec) |totaltime(msec)| > > |---------------|---------------|---------------|---------------| > > |Baseline |live_migration |5657.58 | | > > | |multifdsend_0 |3931.563 | | > > | |multifdsend_1 |4405.273 | | > > | |multifdsend_2 |3941.968 | | > > | |multifdsend_3 |5032.975 | | > > | |multifdsend_4 |4533.865 | | > > | |multifdsend_5 |4530.461 | | > > | |multifdsend_6 |5171.916 | | > > | |multifdsend_7 |4722.769 |41922 | > > |---------------|---------------|---------------|---------------| > > |DSA |live_migration |6129.168 | | > > | |multifdsend_0 |2954.717 | | > > | |multifdsend_1 |2766.359 | | > > | |multifdsend_2 |2853.519 | | > > | |multifdsend_3 |2740.717 | | > > | |multifdsend_4 |2824.169 | | > > | |multifdsend_5 |2966.908 | | > > | |multifdsend_6 |2611.137 | | > > | |multifdsend_7 |3114.732 | | > > | |dsa_completion |3612.564 |32568 | > > |---------------|---------------|---------------|---------------| > > > > Baseline total runtime is calculated by adding up all multifdsend_X > > and live_migration threads runtime. DSA offloading total runtime is > > calculated by adding up all multifdsend_X, live_migration and > > dsa_completion threads runtime. 41922 msec VS 32568 msec runtime and > > that is 23% total CPU usage savings. > > > > Latency > > > > |---------------|---------------|---------------|---------------|---------------|---------------| > > | |total time |down time |throughput > > |transferred-ram|total-ram | > > > > |---------------|---------------|---------------|---------------|---------------|---------------| > > |Baseline |10343 ms |161 ms |41007.00 mbps > > |51583797 kb |102400520 kb | > > > > |---------------|---------------|---------------|---------------|-------------------------------| > > |DSA offload |9535 ms |135 ms |46554.40 mbps > > |53947545 kb |102400520 kb | > > > > |---------------|---------------|---------------|---------------|---------------|---------------| > > > > Total time is 8% faster and down time is 16% faster. > > > > B) Scenario 2: 100% (100GB) zero pages on an 100GB vm. > > > > CPU usage > > |---------------|---------------|---------------|---------------| > > | |comm |runtime(msec) |totaltime(msec)| > > |---------------|---------------|---------------|---------------| > > |Baseline |live_migration |4860.718 | | > > | |multifdsend_0 |748.875 | | > > | |multifdsend_1 |898.498 | | > > | |multifdsend_2 |787.456 | | > > | |multifdsend_3 |764.537 | | > > | |multifdsend_4 |785.687 | | > > | |multifdsend_5 |756.941 | | > > | |multifdsend_6 |774.084 | | > > | |multifdsend_7 |782.900 |11154 | > > |---------------|---------------|-------------------------------| > > |DSA offloading |live_migration |3846.976 | | > > | |multifdsend_0 |191.880 | | > > | |multifdsend_1 |166.331 | | > > | |multifdsend_2 |168.528 | | > > | |multifdsend_3 |197.831 | | > > | |multifdsend_4 |169.580 | | > > | |multifdsend_5 |167.984 | | > > | |multifdsend_6 |198.042 | | > > | |multifdsend_7 |170.624 | | > > | |dsa_completion |3428.669 |8700 | > > |---------------|---------------|---------------|---------------| > > > > Baseline total runtime is 11154 msec and DSA offloading total runtime is > > 8700 msec. That is 22% CPU savings. > > > > Latency > > > > |--------------------------------------------------------------------------------------------| > > | |total time |down time |throughput > > |transferred-ram|total-ram | > > > > |---------------|---------------|---------------|---------------|---------------|------------| > > |Baseline |4867 ms |20 ms |1.51 mbps |565 > > kb |102400520 kb| > > > > |---------------|---------------|---------------|---------------|----------------------------| > > |DSA offload |3888 ms |18 ms |1.89 mbps |565 > > kb |102400520 kb| > > > > |---------------|---------------|---------------|---------------|---------------|------------| > > > > Total time 20% faster and down time 10% faster. > > > > * Testing: > > > > 1. Added unit tests for cover the added code path in dsa.c > > 2. Added integration tests to cover multifd live migration using DSA > > offloading. > > > > Hao Xiang (10): > > meson: Introduce new instruction set enqcmd to the build system. > > util/dsa: Implement DSA device start and stop logic. > > util/dsa: Implement DSA task enqueue and dequeue. > > util/dsa: Implement DSA task asynchronous completion thread model. > > util/dsa: Implement zero page checking in DSA task. > > util/dsa: Implement DSA task asynchronous submission and wait for > > completion. > > migration/multifd: Add new migration option for multifd DSA > > offloading. > > migration/multifd: Enable DSA offloading in multifd sender path. > > util/dsa: Add unit test coverage for Intel DSA task submission and > > completion. > > migration/multifd: Add integration tests for multifd with Intel DSA > > offloading. > > > > Yichen Wang (1): > > util/dsa: Add idxd into linux header copy list. > > > > Yuan Liu (1): > > migration/doc: Add DSA zero page detection doc > > > > .../migration/dsa-zero-page-detection.rst | 290 +++++ > > docs/devel/migration/features.rst | 1 + > > hmp-commands.hx | 2 +- > > include/qemu/dsa.h | 188 +++ > > meson.build | 14 + > > meson_options.txt | 2 + > > migration/migration-hmp-cmds.c | 19 +- > > migration/multifd-zero-page.c | 129 +- > > migration/multifd.c | 29 +- > > migration/multifd.h | 5 + > > migration/options.c | 30 + > > migration/options.h | 1 + > > qapi/migration.json | 32 +- > > scripts/meson-buildoptions.sh | 3 + > > scripts/update-linux-headers.sh | 2 +- > > tests/qtest/migration-test.c | 80 +- > > tests/unit/meson.build | 6 + > > tests/unit/test-dsa.c | 503 ++++++++ > > util/dsa.c | 1112 +++++++++++++++++ > > util/meson.build | 3 + > > 20 files changed, 2427 insertions(+), 24 deletions(-) > > create mode 100644 docs/devel/migration/dsa-zero-page-detection.rst > > create mode 100644 include/qemu/dsa.h > > create mode 100644 tests/unit/test-dsa.c > > create mode 100644 util/dsa.c > > Hi, take a look at make check, there are some tests failing. > > Summary of Failures: > > 16/474 qemu:qtest+qtest-x86_64 / qtest-x86_64/test-hmp > ERROR 0.86s killed by signal 6 SIGABRT > 18/474 qemu:qtest+qtest-ppc64 / qtest-ppc64/test-hmp > ERROR 0.93s killed by signal 6 SIGABRT > 20/474 qemu:qtest+qtest-aarch64 / qtest-aarch64/test-hmp > ERROR 1.30s killed by signal 6 SIGABRT > 21/474 qemu:qtest+qtest-s390x / qtest-s390x/test-hmp > ERROR 0.76s killed by signal 6 SIGABRT > 22/474 qemu:qtest+qtest-riscv64 / qtest-riscv64/test-hmp > ERROR 0.60s killed by signal 6 SIGABRT > > Looks like a double-free due to glib autofree. Here's one sample: > > #0 __GI_abort () at abort.c:49 > #1 0x00007ffff5899c87 in __libc_message (action=do_abort, fmt=0x7ffff59c3138 > "%s\n") at ../sysdeps/posix/libc_fatal.c:155 > #2 0x00007ffff58a1d2a in malloc_printerr (str=0x7ffff59c0e0e "free(): > invalid pointer") at malloc.c:5347 > #3 0x00007ffff58a37d4 in _int_free (av=<optimized out>, p=<optimized out>, > have_lock=0) at malloc.c:4173 > #4 0x00007ffff78c5639 in g_free (mem=0x5555561200f1 > <qemu_mutex_unlock_impl+96>) at ../glib/gmem.c:199 > #5 0x0000555555bdd527 in g_autoptr_cleanup_generic_gfree (p=0x7fffffffd568) > at /usr/include/glib-2.0/glib/glib-autocleanups.h:28 > #6 0x0000555555bdfabc in hmp_migrate_set_parameter (mon=0x7fffffffd6f0, > qdict=0x555558554560) at ../migration/migration-hmp-cmds.c:577 > #7 0x0000555555c1a231 in handle_hmp_command_exec (mon=0x7fffffffd6f0, > cmd=0x5555571e7450 <hmp_cmds+4560>, qdict=0x555558554560) at > ../monitor/hmp.c:1106 > #8 0x0000555555c1a470 in handle_hmp_command (mon=0x7fffffffd6f0, > cmdline=0x5555577ec2f6 "xbzrle-cache-size 64k") at ../monitor/hmp.c:1158 > #9 0x0000555555c1c40e in qmp_human_monitor_command > (command_line=0x5555577ec2e0 "migrate_set_parameter xbzrle-cache-size 64k", > has_cpu_index=false, cpu_index=0, errp=0x7fffffffd800) > at ../monitor/qmp-cmds.c:181 > #10 0x00005555560c7eb6 in qmp_marshal_human_monitor_command > (args=0x7fffe000ac00, ret=0x7ffff4d25da8, errp=0x7ffff4d25da0) at > qapi/qapi-commands-misc.c:347 > #11 0x000055555610e7a4 in do_qmp_dispatch_bh (opaque=0x7ffff4d25e40) at > ../qapi/qmp-dispatch.c:128 > #12 0x000055555613a1b9 in aio_bh_call (bh=0x7fffe0004050) at > ../util/async.c:172 > #13 0x000055555613a2d5 in aio_bh_poll (ctx=0x5555573df400) at > ../util/async.c:219 > #14 0x000055555611b8cd in aio_dispatch (ctx=0x5555573df400) at > ../util/aio-posix.c:424 > #15 0x000055555613a712 in aio_ctx_dispatch (source=0x5555573df400, > callback=0x0, user_data=0x0) at ../util/async.c:361 > #16 0x00007ffff78bf82b in g_main_dispatch (context=0x5555573e3440) at > ../glib/gmain.c:3381 > #17 g_main_context_dispatch (context=0x5555573e3440) at ../glib/gmain.c:4099 > #18 0x000055555613bdae in glib_pollfds_poll () at ../util/main-loop.c:287 > #19 0x000055555613be28 in os_host_main_loop_wait (timeout=0) at > ../util/main-loop.c:310 > #20 0x000055555613bf2d in main_loop_wait (nonblocking=0) at > ../util/main-loop.c:589 > #21 0x0000555555bb455c in qemu_main_loop () at ../system/runstate.c:835 > #22 0x00005555560594d1 in qemu_default_main () at ../system/main.c:37 > #23 0x000055555605950c in main (argc=18, argv=0x7fffffffdc18) at > ../system/main.c:48
Fixed. Interesting that our marco of g_auto(GStrv) won't work in switch-case statements. I switched back to original char **/g_strfreev() to get it working.
