Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
MIME-Version: 1.0
References: <20220913162732.163631-1-xukuohai@huaweicloud.com>
 <f1e14934-dc54-9bf7-501a-89affdb7371e@iogearbox.net> <YzG51Jyd5zhvygtK@arm.com>
 <YzHk1zRf1Dp8YTEe@FVFF77S0Q05N> <970a25e4-9b79-9e0c-b338-ed1a934f2770@huawei.com>
 <YzR5WSLux4mmFIXg@FVFF77S0Q05N> <2cb606b4-aa8b-e259-cdfd-1bfc61fd7c44@huawei.com>
 <CABRcYmKPchvtkkgWhOJ6o3pHVqTWeenGawHfZ2ug8Akdh6NfnQ@mail.gmail.com>
 <7f34d333-3b2a-aea5-f411-d53be2c46eee@huawei.com> <20221005110707.55bd9354@gandalf.local.home>
In-Reply-To: <20221005110707.55bd9354@gandalf.local.home>
From:   Florent Revest <revest@chromium.org>
Date:   Wed, 5 Oct 2022 17:10:33 +0200
Message-ID: <CABRcYmJGY6fp0CtUBYN8BjEDN=r42BPLSBcrxqu491bTRmfm7g@mail.gmail.com>
Subject: Re: [PATCH bpf-next v2 0/4] Add ftrace direct call for arm64
To:     Steven Rostedt <rostedt@goodmis.org>
Cc:     Xu Kuohai <xukuohai@huawei.com>,
        Mark Rutland <mark.rutland@arm.com>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Xu Kuohai <xukuohai@huaweicloud.com>,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
        bpf@vger.kernel.org, Will Deacon <will@kernel.org>,
        Jean-Philippe Brucker <jean-philippe@linaro.org>,
        Ingo Molnar <mingo@redhat.com>,
        Oleg Nesterov <oleg@redhat.com>,
        Alexei Starovoitov <ast@kernel.org>,
        Andrii Nakryiko <andrii@kernel.org>,
        Martin KaFai Lau <martin.lau@linux.dev>,
        Song Liu <song@kernel.org>, Yonghong Song <yhs@fb.com>,
        John Fastabend <john.fastabend@gmail.com>,
        KP Singh <kpsingh@kernel.org>,
        Stanislav Fomichev <sdf@google.com>,
        Hao Luo <haoluo@google.com>, Jiri Olsa <jolsa@kernel.org>,
        Zi Shen Lim <zlim.lnx@gmail.com>,
        Pasha Tatashin <pasha.tatashin@soleen.com>,
        Ard Biesheuvel <ardb@kernel.org>,
        Marc Zyngier <maz@kernel.org>, Guo Ren <guoren@kernel.org>,
        Masami Hiramatsu <mhiramat@kernel.org>
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

On Wed, Oct 5, 2022 at 5:07 PM Steven Rostedt <rostedt@goodmis.org> wrote:
>
> On Wed, 5 Oct 2022 22:54:15 +0800
> Xu Kuohai <xukuohai@huawei.com> wrote:
>
> > 1.3 attach bpf prog with with direct call, bpftrace -e 'kfunc:vfs_write {}'
> >
> > # dd if=/dev/zero of=/dev/null count=1000000
> > 1000000+0 records in
> > 1000000+0 records out
> > 512000000 bytes (512 MB, 488 MiB) copied, 1.72973 s, 296 MB/s
> >
> >
> > 1.4 attach bpf prog with with indirect call, bpftrace -e 'kfunc:vfs_write {}'
> >
> > # dd if=/dev/zero of=/dev/null count=1000000
> > 1000000+0 records in
> > 1000000+0 records out
> > 512000000 bytes (512 MB, 488 MiB) copied, 1.99179 s, 257 MB/s

Thanks for the measurements Xu!

> Can you show the implementation of the indirect call you used?

Xu used my development branch here
https://github.com/FlorentRevest/linux/commits/fprobe-min-args

As it stands, the performance impact of the fprobe based
implementation would be too high for us. I wonder how much Mark's idea
here https://git.kernel.org/pub/scm/linux/kernel/git/mark/linux.git/log/?h=arm64/ftrace/per-callsite-ops
would help but it doesn't work right now.