3 ms·

and I would point out that on my machine (GCC 6.3-based x86-64 Linux) the times are much closer ~ time python2 -c exit real 0m0.014s user 0m0

and I would point out that on my machine (GCC 6.3-based x86-64 Linux) the times are much closer ~ time python2 -c exit real 0m0.014s user 0m0.011s sys 0m0.004s vs. ~ time python3 -c exit real 0m0.022s user 0m0.018s sys 0m0.004s So for me it's more like an 8ms realtime difference, and four milliseconds are spent in the system either way. python2 seems to do about 700 system calls (!) to start up and exit immediately, including enumerating things like gtk-2 and wxwidgets, which boggles the mind, but it is what it is. python3 seems to do about 470 system calls, much less but still bonkers to my mind. Also weird that they take the same ~4ms in the kernel given that python3 calls into the kernel so much less.

kstrauser 9y ago
That's better yet - thanks for sharing! Most of my Python processes run for weeks at a go, so startup time isn't that important to me as long as it's not glacial. But 40ms (on my system) or 22ms (on yours) is totally acceptable for interactive shell usage. Thanks for including the syscall counts. I know they'd been working to reduce that, but I hadn't seen how much progress they'd made yet. Are most of those to malloc() and open()?
- joshuamorton 9y ago
  It absolutely is. Consider that that means that python takes 2-3 frames to start up. I'm not sure one should or could reasonably consider that "slow" for interactive use.
- microcolonel 9y ago
  Mostly open, read, and fstat for python2: ~ strace python2 -c exit 2>&1 | sort | grep "^[a-z_]*[(]" | sed -e "s/^$[a-z_]*$[(].*/\1/" | uniq -c | sort -rn | head -n 8 199 open 98 read 94 fstat 92 stat 68 rt_sigaction 63 close 27 mmap 16 mprotect Mostly stat, rt_sigaction, and read for python3: ~ strace python3 -c exit 2>&1 | sort | grep "^[a-z_]*[(]" | sed -e "s/^$[a-z_]*$[(].*/\1/" | uniq -c | sort -rn | head -n 8 92 stat 68 rt_sigaction 57 read 54 fstat 35 open 35 close 28 mmap 24 lseek Some of this might be noise though, it's possible that it has something to do with the installed packages, not sure exactly.
mkl 9y ago
My times on x86-64 Linux are similar to yours, but on the Windows Subsystem for Linux (which emulates the Linux kernel) it's a different story: $ time python2 -c exit real 0m0.111s user 0m0.016s sys 0m0.078s $ time python3 -c exit real 0m0.063s user 0m0.016s sys 0m0.047s Python 3 is consistently ~twice as fast. Both seem slower, but this is on a small laptop so the absolute measurements may not be comparable. This is on Creators Update.

kstrauser 9y ago

That's better yet - thanks for sharing! Most of my Python processes run for weeks at a go, so startup time isn't that important to me as long as it's not glacial. But 40ms (on my system) or 22ms (on yours) is totally acceptable for interactive shell usage. Thanks for including the syscall counts. I know they'd been working to reduce that, but I hadn't seen how much progress they'd made yet. Are most of those to malloc() and open()?

joshuamorton 9y ago
It absolutely is. Consider that that means that python takes 2-3 frames to start up. I'm not sure one should or could reasonably consider that "slow" for interactive use.
microcolonel 9y ago
Mostly open, read, and fstat for python2: ~ strace python2 -c exit 2>&1 | sort | grep "^[a-z_]*[(]" | sed -e "s/^$[a-z_]*$[(].*/\1/" | uniq -c | sort -rn | head -n 8 199 open 98 read 94 fstat 92 stat 68 rt_sigaction 63 close 27 mmap 16 mprotect Mostly stat, rt_sigaction, and read for python3: ~ strace python3 -c exit 2>&1 | sort | grep "^[a-z_]*[(]" | sed -e "s/^$[a-z_]*$[(].*/\1/" | uniq -c | sort -rn | head -n 8 92 stat 68 rt_sigaction 57 read 54 fstat 35 open 35 close 28 mmap 24 lseek Some of this might be noise though, it's possible that it has something to do with the installed packages, not sure exactly.

mkl 9y ago

My times on x86-64 Linux are similar to yours, but on the Windows Subsystem for Linux (which emulates the Linux kernel) it's a different story: $ time python2 -c exit real 0m0.111s user 0m0.016s sys 0m0.078s $ time python3 -c exit real 0m0.063s user 0m0.016s sys 0m0.047s Python 3 is consistently ~twice as fast. Both seem slower, but this is on a small laptop so the absolute measurements may not be comparable. This is on Creators Update.