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

Masami Hiramatsu
2026-01-30T09:30:27Z

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,

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

--
Masami Hiramatsu (Google) <mhiramat@kernel.org>