On Wed, 4 Feb 2026 09:51:03 +0800 Yaxiong Tian <[email protected]> wrote:
> On my ARM64 platform, I observed that certain tracing module > initializations run for up to 200ms—for example, init_kprobe_trace(). > Analysis reveals the root cause: the execution flow eval_map_work_func() > →trace_event_update_with_eval_map()→trace_event_update_all() > is highly time-consuming. Although this flow is placed in eval_map_wq > for asynchronous execution, it holds the trace_event_sem lock, causing > other modules to be blocked either directly or indirectly. Also in > init_blk_tracer(), this functions require trace_event_sem device_initcall. > > To resolve this issue, I rename `eval_map_wq` and make it global and moved > init_blk_tracer that are related to this lock to run asynchronously on this > workqueue. Also check for kprobe_event= grub parameter; if not provided, > init_kprobe_trace() returns directly. After optimization, boot time is > reduced by approximately 200ms. > > > Based on my analysis and testing, I've identified that only these two > locations significantly impact timing. Other initcall_* functions do not > exhibit relevant lock contention. > > A brief summary of the test results is as follows: > Before this PATCHS: > [ 0.224933] calling init_kprobe_trace+0x0/0xe0 @ 1 > [ 0.455016] initcall init_kprobe_trace+0x0/0xe0 returned 0 after 230080 > usecs > > Only opt setup_boot_kprobe_events() can see: > [ 0.258609] calling init_blk_tracer+0x0/0x68 @ 1 > [ 0.454991] initcall init_blk_tracer+0x0/0x68 returned 0 after 196377 usecs > > After this PATCHS: > [ 0.224940] calling init_kprobe_trace+0x0/0xe0 @ 1 > [ 0.224946] initcall init_kprobe_trace+0x0/0xe0 returned 0 after 3 usecs > skip -------- > [ 0.264835] calling init_blk_tracer+0x0/0x68 @ 1 > [ 0.264841] initcall init_blk_tracer+0x0/0x68 returned 0 after 2 usecs Looks good to me. Acked-by: Masami Hiramatsu (Google) <[email protected]> Thanks! > > --- > Changes in v2: > - Rename eval_map_wq to trace_init_wq. > Changes in v3: > - Opt PATCH 1/3 commit > Changes in v4: > - add trace_async_init boot parameter in patch2 > - add init_kprobe_trace's skip logic in patch3 > - add Suggested-by tag > - Other synchronous optimizations related to trace_async_init > https://lore.kernel.org/all/[email protected]/ > Changes in v5: > - remove trace_async_init boot parameter (patch2 v4) > - remove make Make setup_boot_kprobe_events() asynchronous (patch4 v4) > - Adjusted the patch sequence. > > > Yaxiong Tian (3): > tracing: Rename `eval_map_wq` and allow other parts of tracing use it > blktrace: Make init_blk_tracer() asynchronous > tracing/kprobes: Skip setup_boot_kprobe_events() when no cmdline event > > kernel/trace/blktrace.c | 23 ++++++++++++++++++++++- > kernel/trace/trace.c | 18 +++++++++--------- > kernel/trace/trace.h | 1 + > kernel/trace/trace_kprobe.c | 4 ++++ > 4 files changed, 36 insertions(+), 10 deletions(-) > > -- > 2.25.1 > > -- Masami Hiramatsu (Google) <[email protected]>
