PHP OpCache optimisation

Question

I have enabled opcode caching in php, and it delivers savings in pageloads to the extent of 25%.

I use the excellent OpCache.php GUI tool, and my output is as below.

Keys output is as below.

Hits output is as below.

I am trying to understand some of the basic features in there.
1. What are cached keys and free keys ?
2. How do I reduce my misses ? I read somewhere that opcache_hit_rate should be above 99%. Is there a way to go about this fine tuning. I am currently at 91%
3. How is the visualization to be used ?

I am a beginner to this and would appreciate any help. Many thanks.

Generate a million more requests and don't update your scripts -> the hit rate will be ~99% (it's basic math isn't it?) — zerkms
– zerkms, Commented Aug 2, 2015 at 23:20

user149341 · Accepted Answer · 2015-08-02 23:24:44Z

6

For technical reasons, the PHP opcode cache stores values in a fixed set of "bins", referred to here as "cache keys". The ratio of cache keys to free keys is a rough indicator of how full the cache is.
Your miss rate is high right now because you haven't used your application very much -- by my guess, I'd say there have been around eleven requests to your application since your web server started up. This is normal; the first few requests will always result in misses, because the files involved haven't been loaded into the cache yet.
Generally speaking: ignore it. Unless your application is performing poorly or misbehaving in a way that you believe is related to the cache, you don't need to look at this.

answered Aug 2, 2015 at 23:24

user149341

Sign up to request clarification or add additional context in comments.

2 Comments

Vinu D Over a year ago

Thanks for the clear answer. How did you come to the 11 requests conclusion ? It is in the correct ballpark range. Want to understand how that was estimated. Also, is the output of the tool over a period of time ? Say 24 hours or is it from the beginning of time that opcache was enabled. Thanks

user149341 Over a year ago

The opcache stats are mostly cumulative since server startup. Your screenshot shows 7160 hits on 653 cached scripts; 7160 ÷ 653 ≈ 11.

Collectives™ on Stack Overflow

PHP OpCache optimisation

1 Answer 1

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related