From: Michael Ellerman <patch-notifications@ellerman.id.au>
To: "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com>
Cc: linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
Masami Hiramatsu <mhiramat@kernel.org>,
Ingo Molnar <mingo@kernel.org>
Subject: Re: [v4, 6/6] powerpc: kprobes: prefer ftrace when probing function entry
Date: Tue, 25 Apr 2017 08:47:33 +1000 (AEST) [thread overview]
Message-ID: <3wBhLY159cz9s8Y@ozlabs.org> (raw)
In-Reply-To: <53ebcc66e4a7ccf1c22cd1703afb0e4738f981ea.1492606062.git.naveen.n.rao@linux.vnet.ibm.com>
On Wed, 2017-04-19 at 12:52:28 UTC, "Naveen N. Rao" wrote:
> KPROBES_ON_FTRACE avoids much of the overhead with regular kprobes as it
> eliminates the need for a trap, as well as the need to emulate or
> single-step instructions.
>
> Though OPTPROBES provides us with similar performance, we have limited
> optprobes trampoline slots. As such, when asked to probe at a function
> entry, default to using the ftrace infrastructure.
>
> With:
> # cd /sys/kernel/debug/tracing
> # echo 'p _do_fork' > kprobe_events
>
> before patch:
> # cat ../kprobes/list
> c0000000000daf08 k _do_fork+0x8 [DISABLED]
> c000000000044fc0 k kretprobe_trampoline+0x0 [OPTIMIZED]
>
> and after patch:
> # cat ../kprobes/list
> c0000000000d074c k _do_fork+0xc [DISABLED][FTRACE]
> c0000000000412b0 k kretprobe_trampoline+0x0 [OPTIMIZED]
>
> Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Applied to powerpc next, thanks.
https://git.kernel.org/powerpc/c/24bd909e94776ecce95291bff910f1
cheers
prev parent reply other threads:[~2017-04-24 22:47 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-04-19 12:52 [PATCH v4 0/6] powerpc: add support for KPROBES_ON_FTRACE Naveen N. Rao
[not found] ` <cover.1492606062.git.naveen.n.rao@linux.vnet.ibm.com>
2017-04-19 12:52 ` [PATCH v4 1/6] powerpc: ftrace: minor cleanup Naveen N. Rao
2017-04-23 11:53 ` [v4,1/6] " Michael Ellerman
2017-04-19 12:52 ` [PATCH v4 2/6] powerpc: ftrace: restore LR from pt_regs Naveen N. Rao
2017-04-24 22:47 ` [v4,2/6] " Michael Ellerman
2017-04-19 12:52 ` [PATCH v4 3/6] kprobes: Skip preparing optprobe if the probe is ftrace-based Naveen N. Rao
2017-04-24 22:47 ` [v4, " Michael Ellerman
2017-04-19 12:52 ` [PATCH v4 4/6] powerpc: kprobes: add support for KPROBES_ON_FTRACE Naveen N. Rao
2017-04-24 22:47 ` [v4,4/6] " Michael Ellerman
2017-04-19 12:52 ` [PATCH v4 5/6] powerpc: introduce a new helper to obtain function entry points Naveen N. Rao
2017-04-24 22:47 ` [v4, " Michael Ellerman
2017-04-19 12:52 ` [PATCH v4 6/6] powerpc: kprobes: prefer ftrace when probing function entry Naveen N. Rao
2017-04-24 22:47 ` Michael Ellerman [this message]
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