On Sat, Mar 17 2018, Nguyễn Thái Ngọc Duy jotted:
> v5 changes are small enough that the interdiff is pretty self
> explanatory (there's also a couple commit msg updates).
I've been testing this and it's definitely an improvement. I think it
would be good to get some mention in the commit messages themselves of
the incremental improvement, to that end I wrote this:
$ cat /tmp/howmuch-mem.sh
#!/bin/sh
cd /tmp &&
(
for i in {1..3}
do
/usr/bin/time -f MaxRSS:%M ~/g/git/git --git-dir=/tmp/linux.git
--exec-path=/home/avar/g/git repack -A -d 2>&1
done | grep MaxRSS: | sort -n | head -n 1 | tr '\n' '\t' &&
git git-commit-summary &&
echo
) | tee -a /tmp/git-memory.log
I.e. we repack linux.git (I'd already repacked it once) and do three
runs, and take the lowest RSS size. This yields (I rebased your series
on top of g...@github.com:git/git.git master and pushed it to
g...@github.com:avar/git.git pack-objects-reduce-memory-footprint), via:
git rebase --exec='make -j8 CFLAGS="-O3" && /tmp/howmuch-mem.sh' -i
That gave me, kb on the first column:
MaxRSS:3746648 f23a196dd9 ("pack-objects: a bit of document about struct
object_entry", 2018-03-01)
MaxRSS:3700696 953b6473d7 ("pack-objects: turn type and in_pack_type to
bitfields", 2018-03-01)
MaxRSS:3700404 6cbe573539 ("pack-objects: use bitfield for
object_entry::dfs_state", 2018-03-01)
MaxRSS:3654044 0b93ebcae9 ("pack-objects: use bitfield for
object_entry::depth", 2018-03-01)
MaxRSS:3654040 67a4d48773 ("pack-objects: move in_pack_pos out of struct
object_entry", 2018-03-01) [X]
MaxRSS:3654104 e77319c65a ("pack-objects: move in_pack out of struct
object_entry", 2018-03-01) [X]
MaxRSS:3608096 a72cfcfea3 ("pack-objects: refer to delta objects by index
instead of pointer", 2018-03-01)
MaxRSS:3562212 76eaa779eb ("pack-objects: shrink z_delta_size field in
struct object_entry", 2018-03-05)
MaxRSS:3515164 42e28dd4b3 ("pack-objects: shrink size field in struct
object_entry", 2018-03-05)
MaxRSS:3469440 26eba3ded4 ("pack-objects: shrink delta_size field in
struct object_entry", 2018-03-05)
MaxRSS:3423704 c6493de964 ("pack-objects.h: reorder members to shrink
struct object_entry", 2018-03-12)
I.e. on git.git we end up with just over a a 8.5% reduction, and
interestingly have a slight increase over a past commit in one change,
and one that just makes 4kb of difference (marked via [X] above).
Also, your v0 says it overall saves 260MB of memory. According to this
it's 320MB. You did note some reductions in subsequent patches, but it's
worth calling that out explicitly.
I have a bigger in-house repo that looks like this with this change:
MaxRSS:4753120 f23a196dd9 ("pack-objects: a bit of document about struct
object_entry", 2018-03-01)
MaxRSS:4699084 953b6473d7 ("pack-objects: turn type and in_pack_type to
bitfields", 2018-03-01)
MaxRSS:4699028 6cbe573539 ("pack-objects: use bitfield for
object_entry::dfs_state", 2018-03-01)
MaxRSS:4645452 0b93ebcae9 ("pack-objects: use bitfield for
object_entry::depth", 2018-03-01)
MaxRSS:4645288 67a4d48773 ("pack-objects: move in_pack_pos out of struct
object_entry", 2018-03-01)
MaxRSS:4645548 e77319c65a ("pack-objects: move in_pack out of struct
object_entry", 2018-03-01)
MaxRSS:4591484 a72cfcfea3 ("pack-objects: refer to delta objects by index
instead of pointer", 2018-03-01)
MaxRSS:4537980 76eaa779eb ("pack-objects: shrink z_delta_size field in
struct object_entry", 2018-03-05)
MaxRSS:4484148 42e28dd4b3 ("pack-objects: shrink size field in struct
object_entry", 2018-03-05)
MaxRSS:4430404 26eba3ded4 ("pack-objects: shrink delta_size field in
struct object_entry", 2018-03-05)
MaxRSS:4376148 c6493de964 ("pack-objects.h: reorder members to shrink
struct object_entry", 2018-03-12)
I.e. a tad more than a 7.9% reduction in memory use.
This series also doesn't make a difference to the total runtime (which
is good, just wanted to make sure). On linux.git on my box best out of
three is 1:15.74 before and 1:14.93 after, which is within the margin of
random error.
