Hello!
I noticed that ‘guix shell’ had become relatively slow on cache hits, as
in this example:
--8<---------------cut here---------------start------------->8---
$ time guix shell -D guix -- true
real 0m0.596s
user 0m0.716s
sys 0m0.064s
$ strace -c guix shell -D guix -- true
% time seconds usecs/call calls errors syscall
------ ----------- ----------- --------- --------- ------------------
21.35 0.005453 37 147 20 futex
18.17 0.004641 4641 1 wait4
13.58 0.003470 4 837 mmap
11.59 0.002960 493 6 clone
11.51 0.002940 1 1835 326 newfstatat
9.26 0.002365 2 950 290 openat
7.85 0.002005 3 641 mprotect
2.05 0.000524 0 661 close
2.01 0.000514 3 135 read
1.15 0.000295 0 601 3 lseek
0.33 0.000085 3 25 rt_sigprocmask
0.25 0.000065 3 20 brk
0.22 0.000055 1 28 pread64
0.13 0.000033 4 7 munmap
0.10 0.000025 5 5 rt_sigaction
0.08 0.000020 20 1 arch_prctl
0.08 0.000020 6 3 prlimit64
0.06 0.000016 2 6 1 ioctl
0.06 0.000016 5 3 pipe2
0.05 0.000012 0 16 clock_gettime
0.03 0.000007 2 3 fcntl
0.03 0.000007 7 1 set_tid_address
0.03 0.000007 7 1 set_robust_list
0.02 0.000005 2 2 sched_getaffinity
0.01 0.000002 0 4 write
0.01 0.000002 0 14 getpid
0.00 0.000000 0 2 2 access
0.00 0.000000 0 3 madvise
0.00 0.000000 0 1 execve
0.00 0.000000 0 1 uname
0.00 0.000000 0 1 getcwd
0.00 0.000000 0 115 97 readlink
0.00 0.000000 0 1 sysinfo
0.00 0.000000 0 2 getuid
0.00 0.000000 0 2 geteuid
0.00 0.000000 0 1 utimensat
0.00 0.000000 0 2 getrandom
------ ----------- ----------- --------- --------- ------------------
100.00 0.025544 4 6084 739 total
$ guix describe
Generation 255 Apr 16 2023 22:56:42 (current)
guix 9a5e1dc
repository URL: https://git.savannah.gnu.org/git/guix.git
branch: master
commit: 9a5e1dc1f16f5f8c056e64f2077b035784003673
--8<---------------cut here---------------end--------------->8---
The 950 ‘openat’ calls stem from opening lots of gnu/packages/* files,
which is unnecessary.
This, in turn, comes from (guix scripts pack), which has become a hard
dependency of (guix scripts environment) with commit
b31ea797edb4f6e8c14e8fe790da1319607c5cb1.
I think we should stick to ~0.1s startup time for cached ‘guix shell’,
as described in <https://issues.guix.gnu.org/50960#9>.
Ludo’.
