* Adam Borowski <kilob...@angband.pl> wrote:
> From: Nick Terrell <terre...@fb.com>
>
> Integrates the ZSTD decompression code to the x86 pre-boot code.
>
> Zstandard requires slightly more memory during the kernel decompression
> on x86 (192 KB vs 64 KB), and the memory usage is independent of the
> window size.
>
> Zstandard requires memory proportional to the window size used during
> compression for decompressing the ramdisk image, since streaming mode is
> used. Newer versions of zstd (1.3.2+) list the window size of a file
> with `zstd -lv <file>'. The absolute maximum amount of memory required
> is just over 8 MB.
>
> Signed-off-by: Nick Terrell <terre...@fb.com>
> ---
> Documentation/x86/boot.txt | 6 +++---
> arch/x86/Kconfig | 1 +
> arch/x86/boot/compressed/Makefile | 5 ++++-
> arch/x86/boot/compressed/misc.c | 4 ++++
> arch/x86/boot/header.S | 8 +++++++-
> arch/x86/include/asm/boot.h | 6 ++++--
> 6 files changed, 23 insertions(+), 7 deletions(-)
Acked-by: Ingo Molnar <mi...@kernel.org>
> diff --git a/arch/x86/boot/header.S b/arch/x86/boot/header.S
> index 4c881c850125..af2efb256527 100644
> --- a/arch/x86/boot/header.S
> +++ b/arch/x86/boot/header.S
> @@ -526,8 +526,14 @@ pref_address: .quad LOAD_PHYSICAL_ADDR
> # preferred load addr
> # the size-dependent part now grows so fast.
> #
> # extra_bytes = (uncompressed_size >> 8) + 65536
> +#
> +# ZSTD compressed data grows by at most 3 bytes per 128K, and only has a 22
> +# byte fixed overhead but has a maximum block size of 128K, so it needs a
> +# larger margin.
> +#
> +# extra_bytes = (uncompressed_size >> 8) + 131072
>
> -#define ZO_z_extra_bytes ((ZO_z_output_len >> 8) + 65536)
> +#define ZO_z_extra_bytes ((ZO_z_output_len >> 8) + 131072)
This change would also affect other decompressors, not just ZSTD,
correct?
Might want to split this change out into a separate preparatory patch to
allow it to be bisected to, or at least mention it in the changelog more
explicitly?
Thanks,
Ingo
