* Adam Borowski <kilobyte@xxxxxxxxxx> wrote: > From: Nick Terrell <terrelln@xxxxxx> > > 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 <terrelln@xxxxxx> > --- > 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 <mingo@xxxxxxxxxx> > 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
