From: Rasmus Villemoes linux@rasmusvillemoes.dk
[ Upstream commit 523f3dbc187a9618d4fd80c2b438e4d490705dcd ]
Contrary to expectations, passing a single candidate tag to "git describe" is slower than not passing any --match options.
$ time git describe --debug ... traversed 10619 commits ... v6.12-rc5-63-g0fc810ae3ae1
real 0m0.169s
$ time git describe --match=v6.12-rc5 --debug ... traversed 1310024 commits v6.12-rc5-63-g0fc810ae3ae1
real 0m1.281s
In fact, the --debug output shows that git traverses all or most of history. For some repositories and/or git versions, those 1.3s are actually 10-15 seconds.
This has been acknowledged as a performance bug in git [1], and a fix is on its way [2]. However, no solution is yet in git.git, and even when one lands, it will take quite a while before it finds its way to a release and for $random_kernel_developer to pick that up.
So rewrite the logic to use plumbing commands. For each of the candidate values of $tag, we ask: (1) is $tag even an annotated tag? (2) Is it eligible to describe HEAD, i.e. an ancestor of HEAD? (3) If so, how many commits are in $tag..HEAD?
I have tested that this produces the same output as the current script for ~700 random commits between v6.9..v6.10. For those 700 commits, and in my git repo, the 'make -s kernelrelease' command is on average ~4 times faster with this patch applied (geometric mean of ratios).
For the commit mentioned in Josh's original report [3], the time-consuming part of setlocalversion goes from
$ time git describe --match=v6.12-rc5 c1e939a21eb1 v6.12-rc5-44-gc1e939a21eb1
real 0m1.210s
to
$ time git rev-list --count --left-right v6.12-rc5..c1e939a21eb1 0 44
real 0m0.037s
[1] https://lore.kernel.org/git/20241101113910.GA2301440@coredump.intra.peff.net... [2] https://lore.kernel.org/git/20241106192236.GC880133@coredump.intra.peff.net/ [3] https://lore.kernel.org/lkml/309549cafdcfe50c4fceac3263220cc3d8b109b2.173033...
Reported-by: Sean Christopherson seanjc@google.com Closes: https://lore.kernel.org/lkml/ZPtlxmdIJXOe0sEy@google.com/ Reported-by: Josh Poimboeuf jpoimboe@kernel.org Closes: https://lore.kernel.org/lkml/309549cafdcfe50c4fceac3263220cc3d8b109b2.173033... Tested-by: Josh Poimboeuf jpoimboe@kernel.org Signed-off-by: Rasmus Villemoes linux@rasmusvillemoes.dk Signed-off-by: Masahiro Yamada masahiroy@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- scripts/setlocalversion | 54 +++++++++++++++++++++++++++++------------ 1 file changed, 38 insertions(+), 16 deletions(-)
diff --git a/scripts/setlocalversion b/scripts/setlocalversion index 38b96c6797f40..5818465abba98 100755 --- a/scripts/setlocalversion +++ b/scripts/setlocalversion @@ -30,6 +30,27 @@ if test $# -gt 0 -o ! -d "$srctree"; then usage fi
+try_tag() { + tag="$1" + + # Is $tag an annotated tag? + [ "$(git cat-file -t "$tag" 2> /dev/null)" = tag ] || return 1 + + # Is it an ancestor of HEAD, and if so, how many commits are in $tag..HEAD? + # shellcheck disable=SC2046 # word splitting is the point here + set -- $(git rev-list --count --left-right "$tag"...HEAD 2> /dev/null) + + # $1 is 0 if and only if $tag is an ancestor of HEAD. Use + # string comparison, because $1 is empty if the 'git rev-list' + # command somehow failed. + [ "$1" = 0 ] || return 1 + + # $2 is the number of commits in the range $tag..HEAD, possibly 0. + count="$2" + + return 0 +} + scm_version() { local short=false @@ -61,33 +82,33 @@ scm_version() # stable kernel: 6.1.7 -> v6.1.7 version_tag=v$(echo "${KERNELVERSION}" | sed -E 's/^([0-9]+.[0-9]+).0(.*)$/\1\2/')
+ # try_tag initializes count if the tag is usable. + count= + # If a localversion* file exists, and the corresponding # annotated tag exists and is an ancestor of HEAD, use # it. This is the case in linux-next. - tag=${file_localversion#-} - desc= - if [ -n "${tag}" ]; then - desc=$(git describe --match=$tag 2>/dev/null) + if [ -n "${file_localversion#-}" ] ; then + try_tag "${file_localversion#-}" fi
# Otherwise, if a localversion* file exists, and the tag # obtained by appending it to the tag derived from # KERNELVERSION exists and is an ancestor of HEAD, use # it. This is e.g. the case in linux-rt. - if [ -z "${desc}" ] && [ -n "${file_localversion}" ]; then - tag="${version_tag}${file_localversion}" - desc=$(git describe --match=$tag 2>/dev/null) + if [ -z "${count}" ] && [ -n "${file_localversion}" ]; then + try_tag "${version_tag}${file_localversion}" fi
# Otherwise, default to the annotated tag derived from KERNELVERSION. - if [ -z "${desc}" ]; then - tag="${version_tag}" - desc=$(git describe --match=$tag 2>/dev/null) + if [ -z "${count}" ]; then + try_tag "${version_tag}" fi
- # If we are at the tagged commit, we ignore it because the version is - # well-defined. - if [ "${tag}" != "${desc}" ]; then + # If we are at the tagged commit, we ignore it because the + # version is well-defined. If none of the attempted tags exist + # or were usable, $count is still empty. + if [ -z "${count}" ] || [ "${count}" -gt 0 ]; then
# If only the short version is requested, don't bother # running further git commands @@ -95,14 +116,15 @@ scm_version() echo "+" return fi + # If we are past the tagged commit, we pretty print it. # (like 6.1.0-14595-g292a089d78d3) - if [ -n "${desc}" ]; then - echo "${desc}" | awk -F- '{printf("-%05d", $(NF-1))}' + if [ -n "${count}" ]; then + printf "%s%05d" "-" "${count}" fi
# Add -g and exactly 12 hex chars. - printf '%s%s' -g "$(echo $head | cut -c1-12)" + printf '%s%.12s' -g "$head" fi
if ${no_dirty}; then