guix: Use --cores instead of --max-jobs

In Guix, there are two flags for controlling parallelism:

Note: When I say "derivation," think "package"

--cores=n
  - controls the number of CPU cores to build each derivation. This is
    the value passed to `make`'s `--jobs=` flag.
  - defaults to 0: as many cores as is available

--max-jobs=n
  - controls how many derivations can be built in parallel
  - defaults to 1

Therefore, if set --max-jobs=$MAX_JOBS and don't set --cores, Guix could
theoretically spin up $MAX_JOBS * $(nproc) number of threads, and that's
no good.

So we could either default to --cores=1, --max-jobs=$MAX_JOBS

  - Pro: --cores=1 means that `make` will be invoked with `-j1`,
         avoiding problems with package whose build systems and test
         suites break when running multi-threaded.

  - Con: There will be times when only 1 or 2 derivations can be built
         at a time, because the rest of the dependency graph all depend
         on those 1 or 2 derivations. During these times, the machine
         will be severely under-utilized.

or --cores=$MAX_JOBS, --max-jobs=1

  - Pro: We don't encounter prolonged periods of
         severe under-utilization mentioned above.

  - Con: Many packages' build systems and test suites break when running
         multi-threaded.

or --cores=1, --max-jobs=1 and let the user override with
$ADDITIONAL_GUIX_COMMON_FLAGS
pull/21375/head
Carl Dong 4 years ago
parent 66daf4cb3b
commit d5a71e9785

@ -80,6 +80,50 @@ at the end of the `guix pull`)
export PATH="${HOME}/.config/guix/current/bin${PATH:+:}$PATH"
```
### Controlling the number of threads used by `guix` build commands
By default, the scripts under `./contrib/guix` will invoke all `guix` build
commands with `--cores="$JOBS"`. Note that `$JOBS` defaults to `$(nproc)` if not
specified. However, astute manual readers will also notice that there is a
`--max-jobs=` flag (which defaults to 1 if unspecified).
Here is the difference between `--cores=` and `--max-jobs=`:
> Note: When I say "derivation," think "package"
`--cores=`
- controls the number of CPU cores to build each derivation. This is the value
passed to `make`'s `--jobs=` flag.
`--max-jobs=`
- controls how many derivations can be built in parallel
- defaults to 1
Therefore, the default is for `guix` build commands to build one derivation at a
time, utilizing `$JOBS` threads.
Specifying the `$JOBS` environment variable will only modify `--cores=`, but you
can also modify the value for `--max-jobs=` by specifying
`$ADDITIONAL_GUIX_COMMON_FLAGS`. For example, if you have a LOT of memory, you
may want to set:
```sh
export ADDITIONAL_GUIX_COMMON_FLAGS='--max-jobs=8'
```
Which allows for a maximum of 8 derivations to be built at the same time, each
utilizing `$JOBS` threads.
Or, if you'd like to avoid spurious build failures caused by issues with
parallelism within a single package, but would still like to build multiple
packages when the dependency graph allows for it, you may want to try:
```sh
export JOBS=1 ADDITIONAL_GUIX_COMMON_FLAGS='--max-jobs=8'
```
## Usage
### As a Tool for Deterministic Builds
@ -125,12 +169,16 @@ find output/ -type f -print0 | sort -z | xargs -r0 sha256sum
the actual SDK (e.g. SDK_PATH=$HOME/Downloads/macOS-SDKs instead of
$HOME/Downloads/macOS-SDKs/Xcode-11.3.1-11C505-extracted-SDK-with-libcxx-headers).
* _**MAX_JOBS**_
* _**JOBS**_
Override the number of jobs to run simultaneously, you might want to do so on
a memory-limited machine. This may be passed to:
- `guix` build commands as in `guix environment --cores="$JOBS"`
- `make` as in `make --jobs="$JOBS"`
- `xargs` as in `xargs -P"$JOBS"`
Override the maximum number of jobs to run simultaneously, you might want to
do so on a memory-limited machine. This may be passed to `make` as in `make
--jobs="$MAX_JOBS"` or `xargs` as in `xargs -P"$MAX_JOBS"`. _(defaults to the
value of `nproc` outside the container)_
_(defaults to the value of `nproc` outside the container)_
* _**SOURCE_DATE_EPOCH**_

@ -134,7 +134,7 @@ done
# Determine the maximum number of jobs to run simultaneously (overridable by
# environment)
MAX_JOBS="${MAX_JOBS:-$(nproc)}"
JOBS="${JOBS:-$(nproc)}"
# Usage: host_to_commonname HOST
#
@ -152,7 +152,7 @@ host_to_commonname() {
# Download the depends sources now as we won't have internet access in the build
# container
for host in $HOSTS; do
make -C "${PWD}/depends" -j"$MAX_JOBS" download-"$(host_to_commonname "$host")" ${V:+V=1} ${SOURCES_PATH:+SOURCES_PATH="$SOURCES_PATH"}
make -C "${PWD}/depends" -j"$JOBS" download-"$(host_to_commonname "$host")" ${V:+V=1} ${SOURCES_PATH:+SOURCES_PATH="$SOURCES_PATH"}
done
# Determine the reference time used for determinism (overridable by environment)
@ -164,7 +164,7 @@ time-machine() {
# shellcheck disable=SC2086
guix time-machine --url=https://github.com/dongcarl/guix.git \
--commit=490e39ff303f4f6873a04bfb8253755bdae1b29c \
--max-jobs="$MAX_JOBS" \
--cores="$JOBS" \
--keep-failed \
${SUBSTITUTE_URLS:+--substitute-urls="$SUBSTITUTE_URLS"} \
${ADDITIONAL_GUIX_COMMON_FLAGS} ${ADDITIONAL_GUIX_TIMEMACHINE_FLAGS} \
@ -218,7 +218,7 @@ for host in $HOSTS; do
cat << EOF
INFO: Building commit ${GIT_COMMIT:?not set} for platform triple ${HOST:?not set}:
...using reference timestamp: ${SOURCE_DATE_EPOCH:?not set}
...running at most ${MAX_JOBS:?not set} jobs
...running at most ${JOBS:?not set} jobs
...from worktree directory: '${PWD}'
...bind-mounted in container to: '/bitcoin'
...in build directory: '$(distsrc_for_host "$HOST")'
@ -304,12 +304,12 @@ EOF
${SOURCES_PATH:+--share="$SOURCES_PATH"} \
${BASE_CACHE:+--share="$BASE_CACHE"} \
${SDK_PATH:+--share="$SDK_PATH"} \
--max-jobs="$MAX_JOBS" \
--cores="$JOBS" \
--keep-failed \
${SUBSTITUTE_URLS:+--substitute-urls="$SUBSTITUTE_URLS"} \
${ADDITIONAL_GUIX_COMMON_FLAGS} ${ADDITIONAL_GUIX_ENVIRONMENT_FLAGS} \
-- env HOST="$host" \
MAX_JOBS="$MAX_JOBS" \
JOBS="$JOBS" \
SOURCE_DATE_EPOCH="${SOURCE_DATE_EPOCH:?unable to determine value}" \
${V:+V=1} \
${SOURCES_PATH:+SOURCES_PATH="$SOURCES_PATH"} \

@ -26,7 +26,7 @@ cat << EOF
Required environment variables as seen inside the container:
HOST: ${HOST:?not set}
SOURCE_DATE_EPOCH: ${SOURCE_DATE_EPOCH:?not set}
MAX_JOBS: ${MAX_JOBS:?not set}
JOBS: ${JOBS:?not set}
DISTSRC: ${DISTSRC:?not set}
OUTDIR: ${OUTDIR:?not set}
EOF
@ -173,7 +173,7 @@ esac
####################
# Build the depends tree, overriding variables that assume multilib gcc
make -C depends --jobs="$MAX_JOBS" HOST="$HOST" \
make -C depends --jobs="$JOBS" HOST="$HOST" \
${V:+V=1} \
${SOURCES_PATH+SOURCES_PATH="$SOURCES_PATH"} \
${BASE_CACHE+BASE_CACHE="$BASE_CACHE"} \
@ -267,7 +267,7 @@ mkdir -p "$DISTSRC"
sed -i.old 's/-lstdc++ //g' config.status libtool src/univalue/config.status src/univalue/libtool
# Build Bitcoin Core
make --jobs="$MAX_JOBS" ${V:+V=1}
make --jobs="$JOBS" ${V:+V=1}
# Perform basic ELF security checks on a series of executables.
make -C src --jobs=1 check-security ${V:+V=1}
@ -344,7 +344,7 @@ mkdir -p "$DISTSRC"
{
find "${DISTNAME}/bin" -type f -executable -print0
find "${DISTNAME}/lib" -type f -print0
} | xargs -0 -n1 -P"$MAX_JOBS" -I{} "${DISTSRC}/contrib/devtools/split-debug.sh" {} {} {}.dbg
} | xargs -0 -n1 -P"$JOBS" -I{} "${DISTSRC}/contrib/devtools/split-debug.sh" {} {} {}.dbg
;;
esac

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