Date: Fri, 24 Mar 2017 00:31:17 +0900
From: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
To: Yinghai Lu <yinghai@kernel.org>
Cc: Chao Peng <chao.p.peng@linux.intel.com>,
        "H. Peter Anvin" <hpa@zytor.com>, Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>,
        the arch/x86 maintainers <x86@kernel.org>,
        Michal Marek <mmarek@suse.com>, Kees Cook <keescook@chromium.org>,
        Baoquan He <bhe@redhat.com>, "H.J. Lu" <hjl.tools@gmail.com>,
        Paul Bolle <pebolle@tiscali.nl>,
        Masahiro Yamada <yamada.masahiro@socionext.com>,
        Borislav Petkov <bp@suse.de>,
        Andrew Morton <akpm@linux-foundation.org>,
        Arnd Bergmann <arnd@arndb.de>, Petr Mladek <pmladek@suse.com>,
        "David S. Miller" <davem@davemloft.net>,
        "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
        Andy Lutomirski <luto@kernel.org>,
        Thomas Garnier <thgarnie@google.com>,
        Nicolas Pitre <nicolas.pitre@linaro.org>, Tejun Heo <tj@kernel.org>,
        Daniel Mack <daniel@zonque.org>,
        Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
        Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
        Helge Deller <deller@gmx.de>, Rik van Riel <riel@redhat.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        linux-kbuild <linux-kbuild@vger.kernel.org>
Subject: Re: [PATCH] x86/boot: Support uncompressed kernel
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On (03/23/17 08:07), Yinghai Lu wrote:
> On Thu, Mar 23, 2017 at 5:51 AM, Chao Peng <chao.p.peng@linux.intel.com> wrote:
> > Compressed kernel has its own drawback: uncompressing takes time. Even
> > though the time is short enough to ignore for most cases but for cases that
> > time is critical this is still a big number. In our on-going optimization
> > for kernel boot time, the measured overall kernel boot time is ~90ms while
> > the uncompressing takes ~50ms with gzip.
> >
> > The patch adds a 'CONFIG_KERNEL_RAW' configure choice so the built binary
> > can have no uncompressing at all. The experiment shows:
> >
> >     kernel               kernel size    time in decompress_kernel
> >     compressed (gzip)    3.3M           53ms
> >     uncompressed         14M            3ms
> 
> How about the time difference for bootloader to read kernel from
> flash/disk/network to ram?

there are also faster de-compressors than gzip out there. LZ4, for instance.
LZ4, as far as I remember, can be quite fast, like ~10 times faster than gzip.
have you tested it?

	-ss