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/309549cafdcfe50c4fceac3263220cc3d8b109b2.1730337435.git.jpoimboe@kernel.org/
Showing the changes to scripts (1 of 1 file). Show all
Unified · Split
| @@ -30,6 +30,27 @@ if test $# -gt 0 -o ! -d "$srctree"; then · 29 unmodified lines | ||
| 30 | 30 | usage |
| 31 | 31 | fi |
| 32 | 32 | |
| 33 | +try_tag() { | |
| 34 | + tag="$1" | |
| 35 | + | |
| 36 | + # Is $tag an annotated tag? | |
| 37 | + [ "$(git cat-file -t "$tag" 2> /dev/null)" = tag ] || return 1 | |
| 38 | + | |
| 39 | + # Is it an ancestor of HEAD, and if so, how many commits are in $tag..HEAD? | |
| 40 | + # shellcheck disable=SC2046 # word splitting is the point here | |
| 41 | + set -- $(git rev-list --count --left-right "$tag"...HEAD 2> /dev/null) | |
| 42 | + | |
| 43 | + # $1 is 0 if and only if $tag is an ancestor of HEAD. Use | |
| 44 | + # string comparison, because $1 is empty if the 'git rev-list' | |
| 45 | + # command somehow failed. | |
| 46 | + [ "$1" = 0 ] || return 1 | |
| 47 | + | |
| 48 | + # $2 is the number of commits in the range $tag..HEAD, possibly 0. | |
| 49 | + count="$2" | |
| 50 | + | |
| 51 | + return 0 | |
| 52 | +} | |
| 53 | + | |
| 33 | 54 | scm_version() |
| 34 | 55 | { |
| 35 | 56 | local short=false |
| @@ -61,33 +82,33 @@ scm_version() · 25 unmodified lines | ||
| 61 | 82 | # stable kernel: 6.1.7 -> v6.1.7 |
| 62 | 83 | version_tag=v$(echo "${KERNELVERSION}" | sed -E 's/^([0-9]+\.[0-9]+)\.0(.*)$/\1\2/') |
| 63 | 84 | |
| 85 | + # try_tag initializes count if the tag is usable. | |
| 86 | + count= | |
| 87 | + | |
| 64 | 88 | # If a localversion* file exists, and the corresponding |
| 65 | 89 | # annotated tag exists and is an ancestor of HEAD, use |
| 66 | 90 | # it. This is the case in linux-next. |
| 67 | − tag=${file_localversion#-} | |
| 68 | − desc= | |
| 69 | − if [ -n "${tag}" ]; then | |
| 70 | − desc=$(git describe --match=$tag 2>/dev/null) | |
| 91 | + if [ -n "${file_localversion#-}" ] ; then | |
| 92 | + try_tag "${file_localversion#-}" | |
| 71 | 93 | fi |
| 72 | 94 | |
| 73 | 95 | # Otherwise, if a localversion* file exists, and the tag |
| 74 | 96 | # obtained by appending it to the tag derived from |
| 75 | 97 | # KERNELVERSION exists and is an ancestor of HEAD, use |
| 76 | 98 | # it. This is e.g. the case in linux-rt. |
| 77 | − if [ -z "${desc}" ] && [ -n "${file_localversion}" ]; then | |
| 78 | − tag="${version_tag}${file_localversion}" | |
| 79 | − desc=$(git describe --match=$tag 2>/dev/null) | |
| 99 | + if [ -z "${count}" ] && [ -n "${file_localversion}" ]; then | |
| 100 | + try_tag "${version_tag}${file_localversion}" | |
| 80 | 101 | fi |
| 81 | 102 | |
| 82 | 103 | # Otherwise, default to the annotated tag derived from KERNELVERSION. |
| 83 | − if [ -z "${desc}" ]; then | |
| 84 | − tag="${version_tag}" | |
| 85 | − desc=$(git describe --match=$tag 2>/dev/null) | |
| 104 | + if [ -z "${count}" ]; then | |
| 105 | + try_tag "${version_tag}" | |
| 86 | 106 | fi |
| 87 | 107 | |
| 88 | − # If we are at the tagged commit, we ignore it because the version is | |
| 89 | − # well-defined. | |
| 90 | − if [ "${tag}" != "${desc}" ]; then | |
| 108 | + # If we are at the tagged commit, we ignore it because the | |
| 109 | + # version is well-defined. If none of the attempted tags exist | |
| 110 | + # or were usable, $count is still empty. | |
| 111 | + if [ -z "${count}" ] || [ "${count}" -gt 0 ]; then | |
| 91 | 112 | |
| 92 | 113 | # If only the short version is requested, don't bother |
| 93 | 114 | # running further git commands |
| @@ -95,14 +116,15 @@ scm_version() · 1 unmodified line | ||
| 95 | 116 | echo "+" |
| 96 | 117 | return |
| 97 | 118 | fi |
| 119 | + | |
| 98 | 120 | # If we are past the tagged commit, we pretty print it. |
| 99 | 121 | # (like 6.1.0-14595-g292a089d78d3) |
| 100 | − if [ -n "${desc}" ]; then | |
| 101 | − echo "${desc}" | awk -F- '{printf("-%05d", $(NF-1))}' | |
| 122 | + if [ -n "${count}" ]; then | |
| 123 | + printf "%s%05d" "-" "${count}" | |
| 102 | 124 | fi |
| 103 | 125 | |
| 104 | 126 | # Add -g and exactly 12 hex chars. |
| 105 | − printf '%s%s' -g "$(echo $head | cut -c1-12)" | |
| 127 | + printf '%s%.12s' -g "$head" | |
| 106 | 128 | fi |
| 107 | 129 | |
| 108 | 130 | if ${no_dirty}; then |