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Performance
Arun edited this page 2022-07-22 23:17:05 +05:30
Rick uses a 400TB for multiverse data, and nnn to manage it ;)
Optimization techniques
Significant factors
- quicksort with pre-filters to sort by filename, time, size etc.
- 0 fragmentation - no byte loss while storing file name of directory entries
- no copying of filename strings while sorting/filtering
- entries not matching a filter are moved to the lowest slots to ignore later
- selection handling through optimized bulk memory manipulation
- increased number of open file descriptors
- fast redraw only affected lines to avoid complete refresh
- all the large buffers are aligned
- frequently used structures optimized to facilitate SSE quad-instruction support
- read-ahead request (to kernels supporting the feature)
- fast routines to calculate and render file size
- shifts instead of div and mul (modern compilers do this already)
- optimized memory usage everywhere, buffer re-use
- no floating point arithmetic
- static routines
- controlled binary size
O3level compiler optimization- 0-warning statically-analyzed code (forced
-Wall -Wextra -Werrorin CI) - statically generated hash-table for guaranteed
O(1)extension icon lookups
Rejected options
- replace quicksort with a more aggressive algorithm (favor space over time complexity)
- the difference is not usually perceptible by human beings
- the random load option is also removed to emphasize this
- non-standard calls like
statx()/getdents()/getdents64()- platform-specific,
nnnis POSIX-compliant - man page Description begins with "These are not the interfaces you are interested in."
- platform-specific,
- optimize handling 10K+ entries in a dir
- not a mass use case
- performance with 10K files is good enough today
- SSD/NVMe are the future
- use lazy/background/threaded load
- du, sort and type-to-nav program options require a
stat()on all entries for correctness
- du, sort and type-to-nav program options require a
Selection
Supporting multi-directory selection is technically challenging; nnn uses many optimizations to make it unnoticeable in most cases, but select-all (including filtered) or inversion while already having lots of files selected may take some time.
When tested on Motorola Photon Q (ARM CPU with 13.54 bogomips) and a directory with 10K files, even the most complicated cases we came up with finished within 10 seconds. If the earlier selection was small or continuous, both select all (full as well as on filter) and invert were instant.
Comparison
GNU libc + ncursesw vanilla
Stripped binary (or script) size & memory usage of nnn and some other popular FMs (which existed before nnn) while viewing a directory with 13.5K files (0 directories), sorted by size/du:
BINSZ VIRT RES SHR S %MEM COMMAND
650K 139720 91220 8460 S 1.1 ranger
1M 50496 15328 4076 S 0.2 vifm
1M 72152 12468 7336 S 0.2 mc
110K 15740 4348 2460 S 0.1 nnn -t d
GNU libc + ncursesw + upx custom
Results with aggressive make options, static binary and upx compression:
$ make O_NORL=1 O_NOMOUSE=1 O_NOLC=1 O_NOBATCH=1 O_NOSSN=1 O_NOFIFO=1 O_QSORT=1 O_NOUG=1 static strip $ upx nnn-static $ top BINSZ VIRT RES SHR S %MEM COMMAND 582K 3136 3056 4 S 0.0 nnn-static -cdDEnQrux -t d ~/images // 11K files 582K 2428 2240 4 S 0.0 nnn-static -cdDEnQrux -t d /usr/bin // 1.5K files
musl libc + netbsd-curses vanilla
Results with 1950 files:
$ musl-gcc -O3 -DNORL -I../netbsd-curses/libcurses -o nnn-shared src/nnn.c -Wl,-Bsymbolic-functions -L/opt/netbsd-curses -lcurses -lterminfo $ strip nnn-shared $ musl-gcc -O3 -DNORL -I../netbsd-curses/libcurses -o nnn-static src/nnn.c -Wl,-Bsymbolic-functions -L/opt/netbsd-curses -lcurses -lterminfo -static $ strip nnn-static BINSZ VIRT RES SHR S %MEM COMMAND 102K 1952 1580 868 S 0.0 nnn-shared -dn 354K 1164 824 348 S 0.0 nnn-static -dn
nnn vs. ls
The stripped binary size of ls is 130.7K.
nnn takes less than 50% time to list a directory with 2083 files:
$ time nnn /usr/bin
0.00user 0.01system 0:00.02elapsed 42%CPU (0avgtext+0avgdata 3540maxresident)k
1608inputs+0outputs (3major+325minor)pagefaults 0swaps
$ export LS_COLORS='ex=00:su=00:sg=00:ca=00:'
$ time ls -l /usr/bin
0.01user 0.01system 0:00.05elapsed 47%CPU (0avgtext+0avgdata 3800maxresident)k
784inputs+0outputs (0major+303minor)pagefaults 0swaps
nnn roughly makes one-third the system calls made by ls (all readings taken at cold boot).
$ time strace -c nnn -d /usr/bin | wc -l
% time seconds usecs/call calls errors syscall
------ ----------- ----------- --------- --------- ----------------
92.56 0.014030 7 1989 newfstatat
4.95 0.000751 188 4 getdents
1.19 0.000180 3 57 1 stat
0.53 0.000081 81 1 inotify_add_watch
0.15 0.000023 2 15 close
0.11 0.000017 2 10 brk
0.10 0.000015 1 14 openat
0.08 0.000012 2 6 write
0.07 0.000010 0 23 3 ioctl
0.05 0.000007 0 15 fstat
0.05 0.000007 7 1 1 unlink
0.04 0.000006 1 8 read
0.04 0.000006 0 14 mmap
0.04 0.000006 6 1 inotify_rm_watch
0.03 0.000005 5 1 sysinfo
0.01 0.000002 2 1 lseek
0.00 0.000000 0 2 lstat
0.00 0.000000 0 10 mprotect
0.00 0.000000 0 1 munmap
0.00 0.000000 0 9 rt_sigaction
0.00 0.000000 0 9 7 access
0.00 0.000000 0 1 execve
0.00 0.000000 0 1 arch_prctl
0.00 0.000000 0 1 inotify_init1
------ ----------- ----------- --------- --------- ----------------
100.00 0.015158 2194 12 total
0.01user 0.05system 0:00.08elapsed 84%CPU (0avgtext+0avgdata 3524maxresident)k
4576inputs+0outputs (10major+545minor)pagefaults 0swaps
0
$ export LS_COLORS='ex=00:su=00:sg=00:ca=00:'
$ time strace -c ls -l /usr/bin | wc -l
% time seconds usecs/call calls errors syscall
------ ----------- ----------- --------- --------- ----------------
42.88 0.011274 6 1989 lstat
27.69 0.007281 4 1989 1989 lgetxattr
20.74 0.005454 4 1548 1548 getxattr
5.82 0.001529 3 442 readlink
1.35 0.000355 89 4 getdents
0.38 0.000100 3 31 write
0.24 0.000064 2 33 5 openat
0.18 0.000048 1 34 close
0.17 0.000046 3 17 lseek
0.16 0.000042 1 40 mmap
0.16 0.000041 4 11 munmap
0.11 0.000030 1 30 fstat
0.04 0.000011 2 5 brk
0.04 0.000011 11 1 mremap
0.03 0.000007 0 17 read
0.00 0.000000 0 20 mprotect
0.00 0.000000 0 2 rt_sigaction
0.00 0.000000 0 1 rt_sigprocmask
0.00 0.000000 0 2 2 ioctl
0.00 0.000000 0 12 12 access
0.00 0.000000 0 4 socket
0.00 0.000000 0 4 4 connect
0.00 0.000000 0 1 execve
0.00 0.000000 0 2 2 statfs
0.00 0.000000 0 1 arch_prctl
0.00 0.000000 0 1 futex
0.00 0.000000 0 1 set_tid_address
0.00 0.000000 0 1 set_robust_list
0.00 0.000000 0 1 prlimit64
------ ----------- ----------- --------- --------- ----------------
100.00 0.026293 6244 3562 total
0.02user 0.12system 0:00.13elapsed 106%CPU (0avgtext+0avgdata 3728maxresident)k
3752inputs+0outputs (7major+526minor)pagefaults 0swaps
1989
C vs. other languages
- Python3 vs. C gcc benchmarks
- Go vs. C gcc benchmarks
- Bash script vs. C gcc
/* compare.c */
int main(void)
{
for (int i = 0; i < 1000000; i++)
printf("hello\n");
return 0;
}
$ time -p ./compare
real 1.89
user 0.20 <<
sys 1.25
---------------------------------
# compare.sh
#!/bin/bash
for (( i = 0; i < 1000000; i++ ))
do
echo hello
done
exit 0
$ time -p ./compare.sh
real 5.88
user 4.66 <<
sys 1.21