Low hit rate and cache size

Update: I now followed this step-by-step guide to connect redis through unix socket, but that doesn’t change the behavior much. (maxmemory 512mb)

And what I found out is that loading times of the WP back end are around 6 seconds without redis object cache activated and 10-20 seconds with it activated. And the low hit rates and size shown (2 MB) didn’t change.

There must be a problem somewhere. If you could guide me, I’ll send what ever logs are needed.

Thanks in advance!
Laurent

• This reply was modified 12 months ago by biiissen.
• This reply was modified 12 months ago by biiissen.

Update: I had Yoast Test Helper plugin delete the Yoast Indexables and then rebuilt them. The loading times of the pages improved a lot. We’re back at about 6.5 seconds. What is the link here? I don’t fully understand why this has an impact.

When reloading the products page over and over again I only get 85% hit rate (10866/1921) and these 2MB the plugin shows me in the header bar. How’s that? To my understanding this is exactly what the redis cache and the plugin are there for: serve repeated requests from cache (ideally all from RAM) instead of the DB.

Also I noticed that the graph showing the performance of the redis cache is often empty, although I’m constantly working in the WP back end. Does that fit in the picture somehow?

Thanks again in advance for your help!

It looks like your admin is doing upwards of 80,000 cache lookups, of which 35,000 fail. That’s not normal. Some plugin is wreaking havoc on your site. We typically suggest turning them off one by one to identify the culprit.

Dear Julie,

thanks a lot for your reply. I highly appreciate any input to get this site faster.

That screenshot from the admin was a rare exception I now exchanged a few plugins against other ones with similar functionality. So now, I’m more around 5’000-12’000 look ups in the admin, with hit rates >85%, mostly >90%. And the loading time is more around 6 seconds from which usually less then 10ms is for database queries, so I guess the object cache is doing what it should do.

But now my front end is slower then my back end: (uncached) pages take 6-8 seconds to load. (Cached ones 400-600ms.) Your object cache has hit rates around 99% and the database queries take around 15-25ms. So I guess there too, the object cache is doing what it is supposed to.

Regarding what you said about the 80’000 look ups in the back end, a product list with 12 products had 148’000, a list with 3 products 120’000 and a simple page with a heading and sentence on it, had 90’000 look ups (all three with a header and footer of course). Is that normal or would that explain the loading time that is just annoyingly long.

As instructed I disabled all my plugins one by one and enabled them one by one again. With no plugins the site was fast of course, and with each plugin it gets a little slower. Small plugins don’t slow down the site much, bigger ones like WPML (6 plugins) do add roughly 2 seconds to the loading time, Yoast SEO+Pro+Woo together are about 1.5 seconds. Is that normal behavior? All while my CPU sits idle all the time. I pushed the site as much as I could and the CPU was still 75-90% idle.

If you had any clue in which direction to go, or what to look for, I would be very happy for a hint!

Thanks in advance,
Laurent

I think you may need to hire a performance expert to take a look at your site. Or disable plugins that slow you down. There isn’t much more I can say to this.

Dear Julie,

thank you for your reply.
I was already thinking about that option. Do you have a trust-worthy expert to hire at hand?

In your option is there a way to explain these high numbers in look ups or most there be a massive problem somewhere?

Thanks again for your help!

Kind regards,
Laurent

This guy can help: https://remkusdevries.com

Hi Till,

thank you for the reference. That really looks like sb. who knows how to speed up WP websites.
Let’s see if we can afford him and his crew… ??

Please mark my issue as resolved!

Kind regards,
Laurent