Re: autosave in the background

[<tomas@tuxteam.de>]

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On Tue, Jul 11, 2017 at 10:38:11AM +0100, Sharon Kimble wrote:
> 
> Is it possible for emacs to autosave in the background?
> 
> I have a file that I'm working on which is 3.3mbs in size, using
> org-mode, and whilst I'm writing it *everything*, literally everything,
> stops and pauses, becoming unresponsive until its saved completely.
> Hence my request.

It would make sense first to understand what's going on. Most probably
it isn't "disc" write times. Consider my box, a "netbook" class machine
with a (slow) mechanical disk (and full disk encryption, which means
that disk I/O sends one of both CPUs out fot lunch):

 | tomas@rasputin:~$ time dd if=/dev/zero of=/tmp/foo bs=4096 count=1024
 | 1024+0 records in
 | 1024+0 records out
 | 4194304 bytes (4.2 MB) copied, 0.0192296 s, 218 MB/s
 | 
 | real    0m0.024s
 | user    0m0.004s
 | sys     0m0.016s

That's 4M, so in your case's ballpark.

OK, OK, I cheated: of course the sync to disk is happening in the
background and doesn't count towards the 24 ms above. Now with
sync:

 | tomas@rasputin:~$ time dd if=/dev/zero of=/tmp/foo bs=4096 count=1024 conv=fdatasync
 | 1024+0 records in
 | 1024+0 records out
 | 4194304 bytes (4.2 MB) copied, 0.14341 s, 29.2 MB/s
 | 
 | real    0m0.151s
 | user    0m0.008s
 | sys     0m0.016s

Still "just" 150 ms (and I expect your case to be more the "cheating"
case: I don't think Emacs waits for a sync before coming back).

So there must be something else going on. Perhaps you can profile
a "save file"?

Cheers
- -- tomás

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