Re: Adding a way to disable the stat cache

On Fri, Sep 3, 2021 at 4:08 PM Kevin Lyda <kevin@lyda.ie> wrote: > On Fri, Sep 3, 2021 at 2:34 PM Christian Schneider > <cschneid@cschneid.com> wrote: > > If I remember correctly it was about reducing the number of system > calls. Is this no issue any more? > > Has a quick benchmark been done to see the positive / negative impact of > the stat cache for a typical application? > > In the lifespan of php it really wasn't an issue unless someone was > doing something that wasn't wise - I can't think of a single reason to > stat a file in a tight loop. > > However more importantly the current behaviour returns bad data for > perfectly correct programs. So for example on a unix box... > > <?php > passthru('touch foo'); > if (is_file('foo')) { > echo "Correct\n"; > } > passthru('rm foo'); > if (is_file('foo')) { > echo "Incorrect\n"; > } > ?> > > Now this is a silly toy, but imagine using is_file to see if a > graphics file exists, running an image processing program on it to > modify it, and then using a stat call to get the file length to > populate the Content-Length field - it will almost certainly be wrong. > Just to throw it out there: Maybe we should clear the stat cache when functions in the exec family are used? Even if we allow disabling the stat cache, I think we can easily avoid that particular footgun. And if calls to external binaries are involved we likely don't have to worry about stat overhead. Regards, Nikita