Otherwise, it allocates 2 GB of memory at once. Even though the majority of this memory is never touched, the default heuristic overcommit refuses this request if less than 2 GB of RAM+swap is currently available. This results in "zstd: error 11 : Allocation error : not enough memory" and the kernel failing to build. When the size is specified, zstd will reduce the memory request appropriately. For typical kernel sizes of ~32 MB, the largest mmap request will be reduced to 512 MB, which will succeed on all but the smallest devices. For inputs around this size, --stream-size --no-content-size may slightly decrease the compressed size, or slightly increase it: https://github.com/facebook/zstd/issues/2848. Signed-off-by: Alex Xu (Hello71) <alex_y_xu@xxxxxxxx> --- scripts/Makefile.lib | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib index ca901814986a..c98a82ca38e6 100644 --- a/scripts/Makefile.lib +++ b/scripts/Makefile.lib @@ -466,12 +466,20 @@ quiet_cmd_xzmisc = XZMISC $@ # single pass, so zstd doesn't need to allocate a window buffer. When streaming # decompression is used, like initramfs decompression, zstd22 should likely not # be used because it would require zstd to allocate a 128 MB buffer. +# +# --stream-size to reduce zstd memory usage (otherwise zstd -22 --ultra +# allocates, but does not use, 2 GB) and potentially improve compression. +# +# --no-content-size to save three bytes which we do not use (we use size_append). + +# zstd --stream-size is only supported since 1.4.4 +zstd_stream_size = $(shell $(ZSTD) -1c --stream-size=0 --no-content-size </dev/null >/dev/null 2>&1 && printf '%s' '--stream-size=$(total_size) --no-content-size') quiet_cmd_zstd = ZSTD $@ - cmd_zstd = { cat $(real-prereqs) | $(ZSTD) -19; $(size_append); } > $@ + cmd_zstd = { cat $(real-prereqs) | $(ZSTD) $(zstd_stream_size) -19; $(size_append); } > $@ quiet_cmd_zstd22 = ZSTD22 $@ - cmd_zstd22 = { cat $(real-prereqs) | $(ZSTD) -22 --ultra; $(size_append); } > $@ + cmd_zstd22 = { cat $(real-prereqs) | $(ZSTD) $(zstd_stream_size) -22 --ultra; $(size_append); } > $@ # ASM offsets # --------------------------------------------------------------------------- -- 2.34.0
