> On Nov 24, 2021, at 7:31 AM, Alex Xu (Hello71) <alex_y_xu@xxxxxxxx> wrote: > > 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 > You can add: Tested-by: Nick Terrell <terrelln@xxxxxx> Reviewed-by: Nick Terrell <terrelln@xxxxxx> Best, Nick Terrell
