From: "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com>
To: Masami Hiramatsu <mhiramat@kernel.org>,
Steven Rostedt <rostedt@goodmis.org>
Cc: Anton Blanchard <anton@ozlabs.org>,
linux-kernel@vger.kernel.org,
Peter Zijlstra <peterz@infradead.org>
Subject: Re: [PATCH 2/2] trace/kprobe: Remove limit on kretprobe maxactive
Date: Fri, 18 Jun 2021 14:11:12 +0530 [thread overview]
Message-ID: <1624005597.xbhcy9xr3f.naveen@linux.ibm.com> (raw)
In-Reply-To: <20210618132636.ceef49ba0fd01bd26508f672@kernel.org>
Masami Hiramatsu wrote:
> On Thu, 17 Jun 2021 13:07:13 -0400
> Steven Rostedt <rostedt@goodmis.org> wrote:
>
>> On Thu, 17 Jun 2021 22:04:34 +0530
>> "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com> wrote:
>>
>> > > 2. Move the kretprobe instance pool from kretprobe to struct task.
>> > > This pool will allocates one page per task, and shared among all
>> > > kretprobes. This pool will be allocated when the 1st kretprobe
>> > > is registered. maxactive will be kept for someone who wants to
>> > > use per-instance data. But since dynamic event doesn't use it,
>> > > it will be removed from tracefs and perf.
>> >
>> > Won't this result in _more_ memory usage compared to what we have now?
>>
>> Maybe or maybe not. At least with this approach (or the function graph
>> one), you will allocate enough for the environment involved. If there's
>> thousands of tasks, then yes, it will allocate more memory. But if you are
>> running thousands of tasks, you should have a lot of memory in the machine.
>>
>> If you are only running a few tasks, it will be less than the current
>> approach.
>
> Right, this depends on how many tasks you are running on your machine.
> Anyway, since you may not sure how much maxactive is enough, you will
> set maxactive high, then it can consume more than that. Of course you
> can optimize by trial and error. But that does not guarantee all cases,
> because the number of tasks can be increased while tracing. You might
> need to re-configure it by checking the nmissed count again.
Yes. If we go down this route, we should limit the per-task allocation
to a more reasonable 4k -- powerpc uses 64k pages.
Thanks,
Naveen
next prev parent reply other threads:[~2021-06-18 8:41 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-14 18:03 [PATCH 0/2] trace/kprobe: Two fixes for kretprobes Naveen N. Rao
2021-06-14 18:03 ` [PATCH 1/2] trace/kprobe: Fix count of missed kretprobes in kprobe_profile Naveen N. Rao
2021-06-15 5:47 ` Masami Hiramatsu
2021-06-14 18:03 ` [PATCH 2/2] trace/kprobe: Remove limit on kretprobe maxactive Naveen N. Rao
2021-06-15 9:35 ` Masami Hiramatsu
2021-06-15 17:41 ` Naveen N. Rao
2021-06-16 0:46 ` Masami Hiramatsu
2021-06-16 1:03 ` Steven Rostedt
2021-06-16 2:27 ` Masami Hiramatsu
2021-06-16 15:10 ` Masami Hiramatsu
2021-06-17 16:34 ` Naveen N. Rao
2021-06-17 17:07 ` Steven Rostedt
2021-06-18 4:26 ` Masami Hiramatsu
2021-06-18 8:41 ` Naveen N. Rao [this message]
2021-06-17 16:19 ` Naveen N. Rao
2021-06-18 6:17 ` Masami Hiramatsu
2021-06-18 13:19 ` Naveen N. Rao
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