Re: Questions about OPcache interned strings buffer

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]


Thanks, that is precisely the StackOverflow question I made and linked already :). But sadly neither does the behaviour derived from the code in the answer match the actually observed results from opcache_get_status() I described, nor does it answer why it is as it is.

Not sure what the definition of a buffer overflow should tell me. You mean that the full interned strings buffer is the result of a buffer overflow? Actually I don't think so, there are no errors or problems with it, it just seems to be fully used. I only wonder why the used MiB of the interned strings buffer is higher than the used MiB of the remaining while OPcache, and why it keeps being nearly fully used even when I again double it's size. Somehow there seem to be more strings stored than actually available in all PHP files. Maybe the result of intense other caching layers in Wordpress or phpBB, I recognised large PHP scripts in some of their tmp/cache directories (up to 1 MiB size).

Kind regards, 


-------- Ursprüngliche Nachricht --------
Von: Dziamid Harbatsevich <newads777@xxxxxxxxx>
Datum: 01.12.21 19:50 (GMT+01:00)
An: Micha <micha.faul@xxxxxx>
Betreff: Re: Questions about OPcache interned strings buffer

I think this will help to get closer.

On Sun, Nov 28, 2021 at 5:45 AM Micha <micha.faul@xxxxxx> wrote:
> Hi guys,
> I have two questions regarding the OPcache interned strings bugger, I
> hope this mailing list is the right place to ask them, else feel free to
> redirect me to a more fitting place.
> 1. What is the logic behind the assigned strings buffer size and the
> actually usable size? When using powers of 2, it seems to be exactly 75%
> of it being usable, but for values between powers of 2, the usable
> buffer size seems to increase by exactly what was added to the setting,
> so that the used percentage increases until the next power of 2 is
> reached. So basically it is possible that an increase of the settings
> value leads to a decrease of the actually usable strings buffer. I'm
> just wondering about what the remaining <=25% are used for, whether
> using a power of 2 is preferable, or the opposite to have a batter
> ratio. To avoid confusion it may be reasonable to add the <=25% always
> to the usage statistics output, so that setting and statistics match.
> Also Asked on stackoverflow:
> 2. I have a PHP8.1 instance where I can increase the interned strings
> buffer size as much as I want, it is always nearly fully used based on
> the statistics. Currently it's 256 MiB assigned, 100% used with 512 MiB
> overall OPcache size ~90% used. This doesn't look reasonable, as the
> interned strings buffer is also meant to reduce the actual OPcache usage
> (? bundling strings), so it looks wrong that it is used with more MiB
> than the remaining OPcache. Or is it somehow expected that every smaller
> and larger fraction is a string is stored in the interned strings buffer
> as long as it is available, so that it basically always fills up? If so,
> how can one estimate a good size for ones individual instance?
> Best regards,
> Micha

[Index of Archives]     [PHP Home]     [Apache Users]     [PHP on Windows]     [Kernel Newbies]     [PHP Install]     [PHP Classes]     [Pear]     [Postgresql]     [Postgresql PHP]     [PHP on Windows]     [PHP Database Programming]     [PHP SOAP]

  Powered by Linux