Re: Vim surprisingly slow?

2017-11-15 16:57 GMT+03:00 Tim Chase <vim@tim.thechases.com>:
> On 2017-11-15 08:25, Christian Brabandt wrote:
>> On Mi, 15 Nov 2017, Dominique Pellé wrote:
>> > As highlighted in red, notice that we only write 179,281 bytes to
>> > file "20150425.txt" but we open/write/close/fsync 5004 times.
>> > That repeated I/O patterns kills performance, especially because
>> > of the frequent fsync().
> [snip]
>> > Maybe we can change vim to avoid the constant
>> > open/write/close/fsync on file "20150425.txt" which should speed
>> > it up greatly.
>
> However, my understanding is that the writefile() method should be
> doing the same thing (open, append, close) and that's as fast as I
> expect. Though I could be wrong and writefile() might internally
> cache the file handle.
>
>> Thanks for this nice analysis. It is probably the fsync call that
>> is slowing Vim down. We can avoid the fsync by disabling the
>> 'fsync' option.
>
> Does the writefile() method does an fsync() too? If not, it's a
> strong indicator that the fsync() may be part of the guilty slowness.

Does not, not in Vim. In Neovim this is governed by both &fsync option
(by default it is respected) and additional s/S flags pair which
allows one to select a bit safer option vs faster option.

>
> If the writefile() version does an fsync() we may be barking up the
> wrong tree.
>
> I'll test the patch later today when I'm not about to run out the
> door.
>
> Thanks!
>
> -tim
>
>
>
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