Newsgroups: php.internals
Path: news.php.net
Xref: news.php.net php.internals:85256
Mailing-List: contact internals-help@lists.php.net; run by ezmlm
Received-SPF: pass (pb1.pair.com: domain lerdorf.com designates 209.85.220.44 as permitted sender)
Message-ID: <550B733F.8080600@lerdorf.com>
Date: Thu, 19 Mar 2015 18:09:19 -0700
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.5.0
MIME-Version: 1.0
To: Eric Stenson <ericsten@microsoft.com>, 
 "internals@lists.php.net" <internals@lists.php.net>
References: <BN1PR03MB1052831DBB31612C78A0DB0D0010@BN1PR03MB105.namprd03.prod.outlook.com>
In-Reply-To: <BN1PR03MB1052831DBB31612C78A0DB0D0010@BN1PR03MB105.namprd03.prod.outlook.com>
Content-Type: multipart/signed; micalg=pgp-sha1;
 protocol="application/pgp-signature";
 boundary="JRKOj5rIJsVWxxDa42xLelLwmMr4n83KX"
Subject: Re: [PHP-DEV] [Q] Does PHP have a negative cache for file stat operations?
From: rasmus@lerdorf.com (Rasmus Lerdorf)

--JRKOj5rIJsVWxxDa42xLelLwmMr4n83KX
Content-Type: text/plain; charset=windows-1252
Content-Transfer-Encoding: quoted-printable

On 03/19/2015 01:26 PM, Eric Stenson wrote:
> PHP Internals folks--
>=20
> We're doing some performance work in WinCache, and we're finding that s=
ome frameworks are...uh...enthusiastically using file_exists(), is_file()=
 and is_dir() functions on files/directories that don't exist.  Every. Si=
ngle. Pageload.
>=20
> Does the PHP stat cache include negative cache entries?  If not, why no=
t?
>=20
> Are there any existing extensions that implement a negative cache for f=
ile_exists(), is_file(), et. al.?

We do not do negative caching. This is documented at
http://php.net/manual/en/function.clearstatcache.php where it says:

  You should also note that PHP doesn't cache information about
  non-existent files. So, if you call file_exists() on a file that
  doesn't exist, it will return FALSE until you create the file. If you
  create the file, it will return TRUE even if you then delete the
  file. However unlink() clears the cache automatically.

But, I think you are also missing the fact that the stat cache is
per-request. So your "every single pageload" aspect won't be helped by
adding negative caching to the stat cache. It is still going to stat on
every single page load. It is only multiple identical stats within the
same request that gets caught by the stat cache.

-Rasmus


--JRKOj5rIJsVWxxDa42xLelLwmMr4n83KX
Content-Type: application/pgp-signature; name="signature.asc"
Content-Description: OpenPGP digital signature
Content-Disposition: attachment; filename="signature.asc"

-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1

iEYEARECAAYFAlULcz8ACgkQlxayKTuqOuBajgCeK8F+0Z+dO+7NqEVkFUGLGgYe
CnQAnRPbULHRyCTR436BZdZxwmRyg+fm
=MtHp
-----END PGP SIGNATURE-----

--JRKOj5rIJsVWxxDa42xLelLwmMr4n83KX--