Re: [Filesystem] Directory entry caching

From: Niall Douglas (s_sourceforge_at_[hidden])
Date: 2020-05-05 13:59:11

On 02/05/2020 15:53, Chris Glover via Boost wrote:
> On Thu, Apr 30, 2020 at 3:51 AM Andrey Semashev via Boost <
> boost_at_[hidden]> wrote:
> 
>>
>> It's definitely abandoned. And incomplete, by the looks of it.
>>
>>
> Yes, seems so. If there's interest in finishing this work, I can take a
> look to see if I can commit to that, but if it was abandoned for some other
> reason (not breaking ABI maybe?) then I won't bother.
> 
> Does anyone know the history?

I cannot say for sure, but it was abandoned at around the same time as
LLFIO demonstrated to Beman a way of enumerating directory contents,
with complete stat_t per entry, @ > 4 million entries/sec/core on all
the major platforms. That makes any notion of caching pointless, just
enumerate the entire directory, always.

I've also been arguing strenously before WG21 to deprecate
directory_iterator as fundamentally incorrect ASAP, and I don't think
I've been unsuccessful. Recent papers to reach WG21 proposing sorely
needed improvements to directory_iterator have all been shot down. The
feeling I got in the room was the whole thing needs replacing. My
current hope for proposing std::directory_handle for standardisation is
early 2021.

Niall