[PATCH] D18422: Add Cache Pruning support

[Aaron Ballman via llvm-commits]

On Thu, Mar 24, 2016 at 3:09 PM, Rafael Espíndola
<rafael.espindola at gmail.com> wrote:
> On 24 March 2016 at 15:00, Mehdi Amini <mehdi.amini at apple.com> wrote:
>>
>>> On Mar 24, 2016, at 11:54 AM, Rafael Espíndola <rafael.espindola at gmail.com> wrote:
>>>
>>> On 24 March 2016 at 13:20, Mehdi AMINI via llvm-commits
>>> <llvm-commits at lists.llvm.org> wrote:
>>>> joker.eph added a comment.
>>>>
>>>> This will not help with the access to `StatBuf.st_atime`.
>>>
>>> Note that atime is not very dependable. I think most linux systems
>>> these days use relatime for example.
>>
>> Is it detectable? Could we "touch" the file to update mtime?
>
> That relatime is not updated? I guess it is possible to write a test, yes.
>
> The man page of mount says:
>
> -----------------------------------------------------------------------------------
>     relatime
>               Update  inode  access times relative to modify or change
> time.  Access time is only updated if the previous access time was
> earlier than the current modify or change time.  (Similar to noatime,
> but it doesn't break mutt or other applications that need to know if a
> file has been
>               read since the last time it was modified.)
>
>               Since Linux 2.6.30, the kernel defaults to the behavior
> provided by this option (unless noatime was specified), and the
> strictatime option is required to obtain traditional semantics.  In
> addition, since Linux 2.6.30, the file's last access time is always
> updated if it is  more
>               than 1 day old.
> ------------------------------------------------------------------------------
>
> Aaron, is atime available on windows?

There is an st_atime field for struct stat that works on NTFS file
systems but not FAT. I'm not certain what its resolution is, however.

~Aaron