This patch proposes to warn users about the negative performance impact of CC_OPTIMIZE_FOR_SIZE (compiling with -Os instead of -O2). For the moment, we are just advising users not to select this option, but extra details would be useful.
I made some experiments with this option. All of them yielded degraded overall boot time. The kernel is smaller and hence is copied and started earlier, but the benefits are quickly offset by the slower kernel code. Even the total boot time is usually worse than with a regular kernel. Here are my latest results, on Atmel SAMA5D3 Xplained (ARM), Linux 3.10, gzip compressed kernel: Timestamp O2 Os Diff Starting kernel 4.307 s 5.593 s -94 ms Starting init 4.213 s 5.549 s -44 ms Login prompt 21.085 s 22.900 s +1.815 s Michael Opdenacker (1): init/Kconfig: improve CC_OPTIMIZE_FOR_SIZE documentation init/Kconfig | 14 +++++++++++++- 1 file changed, 13 insertions(+), 1 deletion(-) -- 1.8.3.2 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
