On Fri, Dec 20, 2024 at 8:29 PM Larry Garfield <la...@garfieldtech.com> wrote:
> Background: PHP has a not-often-considered feature, the stat-cache. That > is, the runtime caches the OS stat() call for files, so that subsequent > reads on the same file can be faster. However, it's even less realized > that it's a single-file cache. It literally only applies when you try to > do two file-infomation operations on the same file in rapid succession, > without any other file reads in between. > > For more info: > https://tideways.com/profiler/blog/the-php-stat-cache-explained > > Because it's so rarely relevant, in the cases it is relevant, it can be > quite a surprise, and a surprise causing weird and hard to explain caching > bugs in applications. > > The cache also dates from 20 years ago, when Rasmus added it (and the > realpath cache) in Yahoo's forked PHP 4, and then it got integrated into > PHP 5. However, hard drives are vastly faster than they were then, and > operating systems are vastly more efficient than they were then. > > There's been some discussion about making the cache disable-able, though > the consensus now seems to be leaning toward getting rid of it outright: > > https://github.com/php/php-src/pull/17178 > > Arnaud ran some quick benchmarks and found that disabling it has a less > than 1% impact on Symfony and WordPress. > > https://github.com/php/php-src/pull/17178#issuecomment-2554323572 > > Before we go any further, is there appetite among the voting population to > remove it? clearstatcache() and similar functions would get stubbed out as > no-ops, but otherwise we'd just hand the responsibility back to the OS > where it belongs, which seems so far like it would be almost an > unmeasurable performance difference but remove some surprise complexity. > > Would you support such a removal? > What additional data would you need to make the case for such removal? > > -- > Larry Garfield > la...@garfieldtech.com This gets a +1 from me. I've had bugs that I suspected were caused by this cache, but I was never able to confirm it until putting clearstatcache() in production. That's not a workflow I'd like to follow, and it has wasted enough of my time.
