Re: [RFC PATCH 0/4] Add support for LZ4-compressed kernels


H. Peter Anvin <hpa@...>
 

On 01/29/2013 02:15 AM, Russell King - ARM Linux wrote:
On Mon, Jan 28, 2013 at 02:25:10PM -0800, Andrew Morton wrote:
What's this "with enabled unaligned memory access" thing? You mean "if
the arch supports CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS"? If so,
that's only x86, which isn't really in the target market for this
patch, yes?

It's a lot of code for a 50ms boot-time improvement. Does anyone have
any opinions on whether or not the benefits are worth the cost?
Well... when I saw this my immediate reaction was "oh no, yet another
decompressor for the kernel". We have five of these things already.
Do we really need a sixth?

My feeling is that we should have:
- one decompressor which is the fastest
- one decompressor for the highest compression ratio
- one popular decompressor (eg conventional gzip)

And if we have a replacement one for one of these, then it should do
exactly that: replace it. I realise that various architectures will
behave differently, so we should really be looking at numbers across
several arches.

Otherwise, where do we stop adding new ones? After we have 6 of these
(which is after this one). After 12? After the 20th?
The only concern I have with that is if someone paints themselves into a corner and absolutely wants, say, LZO.

Otherwise, per your list it pretty much sounds like we should have lz4, gzip, and xz.

-hpa

--
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel. I don't speak on their behalf.

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