[PATCH] perf tools: Further speed up the perf build

There's another source of overhead in the perf version string generator: git update-index -q --refresh ... which will iterate the whole checked out tree. This can be pretty slow on NFS volumes, but takes some time even with local SSD disks and a fully cached kernel tree: $ perf stat

[PATCH] perf tools: Further speed up the perf build

There's another source of overhead in the perf version string generator: git update-index -q --refresh ... which will iterate the whole checked out tree. This can be pretty slow on NFS volumes, but takes some time even with local SSD disks and a fully cached kernel tree: $ perf stat