Alex Bennée [off-list ref] writes:
41.58% git libcrypto.so.1.0.0 [.] sha1_block_data_order_ssse3
33.62% git libz.so.1.2.3.4 [.] inflate_fast
10.39% git libz.so.1.2.3.4 [.] adler32
2.03% git [kernel.kallsyms] [k] clear_page_c
Do you have any large blobs in the repo that are referenced directly by
a tag?
Because this just so happens to exactly reproduce your symptoms:
# in a random git.git
$ time git describe --debug
[...]
real 0m0.390s
user 0m0.037s
sys 0m0.011s
$ git tag big1 $(dd if=/dev/urandom bs=1M count=512 | git hash-object -w --stdin)
512+0 records in
512+0 records out
536870912 bytes (537 MB) copied, 45.5088 s, 11.8 MB/s
$ time git describe --debug
[...]
real 0m1.875s
user 0m1.738s
sys 0m0.129s
$ git tag big2 $(dd if=/dev/urandom bs=1M count=512 | git hash-object -w --stdin)
512+0 records in
512+0 records out
536870912 bytes (537 MB) copied, 44.972 s, 11.9 MB/s
$ time git describe --debugsuche zur Beschreibung von HEAD
[...]
real 0m3.620s
user 0m3.357s
sys 0m0.248s
(I actually ran the git-describe invocations more than once to ensure
that they are again cache-hot.)
git-describe should probably be fixed to avoid loading blobs, though I'm
not sure off hand if we have any infrastructure to infer the type of a
loose object without inflating it. (This could probably be added by
inflating only the first block.) We do have this for packed objects, so
at least for packed repos there's a speedup to be had.
--
Thomas Rast
trast@{inf,student}.ethz.ch
On 30 May 2013 16:33, Thomas Rast [off-list ref] wrote:
Alex Bennée [off-list ref] writes:
quoted
41.58% git libcrypto.so.1.0.0 [.] sha1_block_data_order_ssse3
33.62% git libz.so.1.2.3.4 [.] inflate_fast
10.39% git libz.so.1.2.3.4 [.] adler32
2.03% git [kernel.kallsyms] [k] clear_page_c
Do you have any large blobs in the repo that are referenced directly by
a tag?
Most probably. I've certainly done a bunch of releases (which are tagged) were
the last thing that was updated was an FPGA image.
Because this just so happens to exactly reproduce your symptoms:
# in a random git.git
$ time git describe --debug
[...]
real 0m0.390s
user 0m0.037s
sys 0m0.011s
$ git tag big1 $(dd if=/dev/urandom bs=1M count=512 | git hash-object -w --stdin)
512+0 records in
512+0 records out
536870912 bytes (537 MB) copied, 45.5088 s, 11.8 MB/s
$ time git describe --debug
[...]
real 0m1.875s
user 0m1.738s
sys 0m0.129s
$ git tag big2 $(dd if=/dev/urandom bs=1M count=512 | git hash-object -w --stdin)
512+0 records in
512+0 records out
536870912 bytes (537 MB) copied, 44.972 s, 11.9 MB/s
$ time git describe --debugsuche zur Beschreibung von HEAD
[...]
real 0m3.620s
user 0m3.357s
sys 0m0.248s
(I actually ran the git-describe invocations more than once to ensure
that they are again cache-hot.)
That looks pretty promising as a replication.
git-describe should probably be fixed to avoid loading blobs, though I'm
not sure off hand if we have any infrastructure to infer the type of a
loose object without inflating it. (This could probably be added by
inflating only the first block.) We do have this for packed objects, so
at least for packed repos there's a speedup to be had.
Will it be loading the blob for every commit it traverses or just ones that hit
a tag? Why does it need to load the blob at all? Surely the commit
tree state doesn't
need to be walked down?
--
Thomas Rast
trast@{inf,student}.ethz.ch
--
Alex, homepage: http://www.bennee.com/~alex/