[Buildroot] [PATCH v2 1/1] fs/common.mk: enable multithreaded xz compression

Matthew Weber matthew.weber at rockwellcollins.com
Thu Jan 24 15:01:56 UTC 2019


James,


On Thu, Jan 24, 2019 at 2:28 AM <james.hilliard1 at gmail.com> wrote:
>
> From: James Hilliard <james.hilliard1 at gmail.com>
>
> xz help indicates only 1 thread is used unless we set threads:
> -T, --threads=NUM   use at most NUM threads; the default is 1; set to 0
>                     to use as many threads as there are processor cores
>
> Signed-off-by: James Hilliard <james.hilliard1 at gmail.com>
>

Reviewed-by: Matthew Weber <matthew.weber at rockwellcollins.com>

> ---
> Changes v1 -> v2:
>   - use PARALLEL_JOBS to determine how many threads to compress with
>   - disable multithreaded compression for reproducible builds
> ---
>  fs/common.mk | 4 ++++
>  1 file changed, 4 insertions(+)
>
> diff --git a/fs/common.mk b/fs/common.mk
> index a560417..76da6d8 100644
> --- a/fs/common.mk
> +++ b/fs/common.mk
> @@ -106,7 +106,11 @@ endif
>  ifeq ($$(BR2_TARGET_ROOTFS_$(2)_XZ),y)
>  ROOTFS_$(2)_DEPENDENCIES += host-xz
>  ROOTFS_$(2)_COMPRESS_EXT = .xz
> +ifeq ($(BR2_REPRODUCIBLE),y)
>  ROOTFS_$(2)_COMPRESS_CMD = xz -9 -C crc32 -c
> +else
> +ROOTFS_$(2)_COMPRESS_CMD = xz -T $(PARALLEL_JOBS) -9 -C crc32 -c

I double checked this logic below in package/Makefile.in for creating
PARALLEL_JOBS still made sense for the use of the value above.

# If BR2_JLEVEL is 0, scale the maximum concurrency with the number of
# CPUs. An additional job is used in order to keep processors busy
# while waiting on I/O.
# If the number of processors is not available, assume one.
ifeq ($(BR2_JLEVEL),0)
PARALLEL_JOBS := $(shell echo \
        $$((1 + `getconf _NPROCESSORS_ONLN 2>/dev/null || echo 1`)))
else
PARALLEL_JOBS := $(BR2_JLEVEL)
endif


Matt



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