Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::3:6 as permitted sender) client-ip=2620:137:e000::3:6;
From:   Yuan Tan <tanyuan@tinylab.org>
To:     falcon@tinylab.org
Cc:     arnd@arndb.de, linux-kernel@vger.kernel.org,
        linux-mips@vger.kernel.org, linux-riscv@lists.infradead.org,
        linux@weissschuh.net, palmer@rivosinc.com,
        paul.walmsley@sifive.com, paulburton@kernel.org,
        paulmck@kernel.org, tim.bird@sony.com, tsbogend@alpha.franken.de,
        w@1wt.eu
Subject: Re: [PATCH v1 0/7] DCE/DSE: Add Dead Syscalls Elimination support, part1
Date:   Sat, 30 Sep 2023 17:31:32 +0800
Message-Id: <20230930093132.2166-1-tanyuan@tinylab.org>
In-Reply-To: <cover.1695679700.git.falcon@tinylab.org>
References: <cover.1695679700.git.falcon@tinylab.org>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Feedback-ID: bizesmtp:tinylab.org:qybglogicsvrgz:qybglogicsvrgz5a-1
Precedence: bulk

I don't know why linux-kernel@vger.kernel.org reject my email send out by
thunderbird. So here I am resending this mail with git send-email.

Here is a test result about DEAD_CODE_DATA_ELIMINATION (DCE) and dead syscalls
elimination (DSE). It's based on config[1] and a simple hello.c initramfs.

In the DSE test, we set CONFIG_SYSCALLS_USED="sys_write sys_exit
sys_reboot," which is used by hello.c to simply print "Hello" then exit
and shut down qemu.


|                                    | syscall remain | vmlinux size     | vmlinux after strip |
| ---------------------------------- | -------------- | ---------------- | ------------------- |
| disable DCE                        | 236            | 2559632          | 1963400             |
| enable DCE                         | 208            | 2037384 (-20.4%) | 1485776 (-24.3%)    |
| enable DCE and DSE(SHE_GROUP)      | 3              | 1856640 (-27.6%) | 1354424 (-31.0%)    |
| enable DCE and DSE(SHE_LINK_ORDER) | 3              | 1856664 (-27.6%) | 1354424 (-31.0%)    |

It shows that dead syscalls elimination can save 7% of space based on DCE.

[1]: https://pastebin.com/KG4fd7aT