Re: [PATCH v4 5/5] blktrace: Make init_blk_tracer() asynchronous when trace_async_init set

Yaxiong Tian
2026-01-30T09:59:42Z

在 2026/1/30 17:30, Masami Hiramatsu (Google) 写道:
> On Thu, 29 Jan 2026 15:29:58 -0500
> Steven Rostedt <rostedt@goodmis.org> wrote:
>
>> On Wed, 28 Jan 2026 19:25:46 -0700
>> Jens Axboe <axboe@kernel.dk> wrote:
>>
>>> On Jan 28, 2026, at 5:40 PM, Steven Rostedt <rostedt@goodmis.org> wrote:
>>>> ﻿
>>>> Jens,
>>>>
>>>> Can you give me an acked-by on this patch and I can take the series through
>>>> my tree.
>>> On phone, hope this works:
>>>
>>> Acked-by: Jens Axboe <axboe@kernel.dk>
>> Thanks!
>>
>>>> Or perhaps this doesn't even need to test the trace_async_init flag and can
>>>> always do the work queue? Does blk_trace ever do tracing at boot up? That
>>>> is, before user space starts?
>>> Not via the traditonal way of running blktrace.
>> Masami and Yaxiong,
>>
>> I've been thinking about this more and I'm not sure we need the
>> trace_async_init kernel parameter at all. As blktrace should only be
>> enabled by user space, it can always use the work queue.
>>
>> For kprobes, if someone is adding a kprobe on the kernel command line, then
>> they are already specifying that tracing is more important.
>>
>> Patch 3 already keeps kprobes from being an issue with contention of the
>> tracing locks, so I don't think it ever needs to use the work queue.
>>
>> Wouldn't it just be better to remove the trace_async_init and make blktrace
>> always use the work queue and kprobes never do it (but exit out early if
>> there were no kprobes registered)?
> Yeah, for kprobes event case, that sounds good to me. I think [3/5] is
> enough to speed it up if user does not define kprobe events on cmdline.
>
> Thank you,

Agreed.

Hi Jens：

what do you think about this proposal (making blktrace always use the
work queue)?

>
>> That is, remove patch 2 and 4 and make this patch always use the work queue.
>>
>> -- Steve
>