Re: file born 30 seconds after its creation on ext4 - bug?
On 2022-04-26 12:47:53 -0500, Nicholas Geovanis wrote:
> On Tue, Apr 26, 2022 at 12:37 PM Nicholas Geovanis <nickgeovanis@gmail.com>
> wrote:
>
> > On Tue, Apr 26, 2022 at 8:45 AM Vincent Lefevre <vincent@vinc17.net>
> > wrote:
> >
> >> On an ext4 filesystem, I got a file born 30 seconds after its
> >> actual creation. Is this a bug?
> >>
> >
> > Only experimentation can really back me up on this, but consider the
> > following:
> >
> > Every time you use the "|" operator or the ";" separator on a command-line,
> > new processes are being spawned. Which wait to be dispatched on a core.
> > But you are not serializing the dispatch of those processes, and
> > especially with
> > 16 fast cores, you can't predict their order of execution.
> >
>
> A couple more observations:
> (1) It looks like you're trying to observe behavior in the very same
> filesystem in which
> the running executable is loaded from and its log files are being
> written-to. That's
> alot of variables in motion at once.
>
> (2) Yes, the "|" is in a sense serializing I/O in "lt|head". But the
> filesystem is syncing
> buffered and disk-based content separately from that.
There are no parallel writes to the file, i.e. everything is
serialized from this point of view.
--
Vincent Lefèvre <vincent@vinc17.net> - Web: <https://www.vinc17.net/>
100% accessible validated (X)HTML - Blog: <https://www.vinc17.net/blog/>
Work: CR INRIA - computer arithmetic / AriC project (LIP, ENS-Lyon)
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