Re: [PATCH] x86/boot: Support uncompressed kernel

[Arnd Bergmann]

On Mon, Mar 27, 2017 at 1:47 PM, Michal Marek <mmarek@xxxxxxxx> wrote:
> Dne 27.3.2017 v 09:58 Sebastian Andrzej Siewior napsal(a):
>> On 2017-03-24 13:35:40 [+0800], Chao Peng wrote:
>>>
>>>>>>     kernel               kernel size    time in decompress_kernel
>>>>>>     compressed (gzip)    3.3M           53ms
>>>>>>     uncompressed         14M            3ms
>>>>>
>>> Exactly, LZ4 is the fastest. It takes 16ms to complete the
>>> decompression. Still sounds a little longer when compared to
>>> uncompressed kernel.
>>
>> Are we seriously talking here about one-time improvement of 13ms
>> boot time?
>
> If the use case is launching new VM instances continuously, then
> compressing the kernel image is about as useful as compressing /bin/bash.

I guess the next step would be to use CONFIG_XIP_KERNEL on x86,
which requires an uncompressed kernel but has the additional advantage
of sharing the read-only sections of the kernel image across virtual
machines, resulting in better RAM and cache usage.

        Arnd