git: Globally limit threads used by git-pack-objects(1)

By default, git-pack-objects(1) will spawn as many threads as there are
logical CPU cores on the machine. While this typically makes sense on a
client's machine because a client will want the command to finish as
fast as possible, on the server-side this is less of a good idea because
it can easily impact other, concurrently running Git commands.

This is why we have started to limit the number of threads this command
may use when performing repository maintenance. Packing of objects is in
no way limited to maintenance though, but it's also executed e.g. when
serving packfiles.

Let's globally limit the number of threads git-pack-objects(1) uses by
injecting the `pack.threads` configuration into all commands which may
generate packfiles.

Changelog: performance

2 files changed, 0 insertions, 32 deletions

diff --git a/internal/gitaly/service/repository/repack.go b/internal/gitaly/service/repository/repack.go
index 18415d4ba..6ba97185d 100644
--- a/internal/gitaly/service/repository/repack.go
+++ b/internal/gitaly/service/repository/repack.go
@@ -3,11 +3,9 @@ package repository
 import (
 	"context"
 	"fmt"
-	"math"
 
 	"github.com/prometheus/client_golang/prometheus"
 	gitalyerrors "gitlab.com/gitlab-org/gitaly/v14/internal/errors"
-	"gitlab.com/gitlab-org/gitaly/v14/internal/git"
 	"gitlab.com/gitlab-org/gitaly/v14/internal/git/housekeeping"
 	"gitlab.com/gitlab-org/gitaly/v14/internal/helper"
 	"gitlab.com/gitlab-org/gitaly/v14/proto/go/gitalypb"
@@ -25,14 +23,6 @@ func init() {
 	prometheus.MustRegister(repackCounter)
 }
 
-// log2Threads returns the log-2 number of threads based on the number of
-// provided CPUs. This prevents repacking operations from exhausting all
-// available CPUs and increasing request latency
-func log2Threads(numCPUs int) git.ValueFlag {
-	n := math.Max(1, math.Floor(math.Log2(float64(numCPUs))))
-	return git.ValueFlag{Name: "--threads", Value: fmt.Sprint(n)}
-}
-
 func (s *server) RepackFull(ctx context.Context, in *gitalypb.RepackFullRequest) (*gitalypb.RepackFullResponse, error) {
 	if in.GetRepository() == nil {
 		return nil, helper.ErrInvalidArgument(gitalyerrors.ErrEmptyRepository)
diff --git a/internal/gitaly/service/repository/repack_test.go b/internal/gitaly/service/repository/repack_test.go
index 7e73290a6..d7efb78dc 100644
--- a/internal/gitaly/service/repository/repack_test.go
+++ b/internal/gitaly/service/repository/repack_test.go
@@ -300,25 +300,3 @@ func TestRepackFullDeltaIslands(t *testing.T) {
 		return err
 	})
 }
-
-func TestLog2Threads(t *testing.T) {
-	t.Parallel()
-	for _, tt := range []struct {
-		cpus    int
-		threads string
-	}{
-		{1, "1"},
-		{2, "1"},
-		{3, "1"},
-		{4, "2"},
-		{8, "3"},
-		{9, "3"},
-		{13, "3"},
-		{16, "4"},
-		{27, "4"},
-		{32, "5"},
-	} {
-		actualThreads := log2Threads(tt.cpus)
-		require.Equal(t, tt.threads, actualThreads.Value)
-	}
-}