Moodle in English: Moodle Performance Problems (split)

Moodle Performance Problems (split)

by Pupil Senpro - Tuesday, December 1, 2015, 5:55 PM

Hello Fellow,
I'm also having problem regarding my Moodle performance.
My current Environment is :

- 2 Server EC2 type small (Memory 2GB), and using ELB for the load balancer
- 2 instances of memcached (512 MB & 1 GB) on different ports, one instance dedicated to
sessions and one instance to MUC
- for the Database server I use RDS - Mysql type Micro (Memory 1GB)

I think It would be fast enough. But When I try access and reloading a page multiple time here is the execution time (from XHprof).

XHProf - 1

Why I say it not fast enough?
Because when I try another environment with just using 1 instance EC2 type small (Memory 2GB), no use of memcached, and same type of RDS. I'm found this execution time.

XHprof - 2

It almost 2 times faster.
When I see the full graph I'm find that the problem is when get object from memcached & mysql.

Culprit - 1

Culprit - 2

Do you have any suggestion Regarding my problem?
Thanks.

Re: Moodle Performance Problems (split)

by Howard Miller - Tuesday, December 1, 2015, 6:11 PM

I split this from another (unrelated) discussion to avoid confusion.

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Re: Moodle Performance Problems (split)

by Howard Miller - Tuesday, December 1, 2015, 6:12 PM

"2 Server EC2 type small (Memory 2GB)"

No chance! From what I remember of trying Moodle on one of those before, it doesn't work. Insufficient resources.

Plus, why would you want to load-balance two tiny servers. It doesn't strike me as being well thought out tbh.

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Re: Moodle Performance Problems (split)

by Pupil Senpro - Tuesday, December 1, 2015, 6:44 PM

So, what is the appropriate memory for the server?
I'm quite new in Installing Moodle.

But from this article https://docs.moodle.org/29/en/Installing_Moodle#Requirements
I'm found that 1 GB it's enough.

Why I use 2 server?, I use it to avoid Single point of Failure.
to increase the Availability.

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Re: Moodle Performance Problems (split)

by Howard Miller - Tuesday, December 1, 2015, 6:56 PM

Single point of failure - like your database? Like the load-balancer?

It's *very* difficult to create a genuinely failure proof Moodle site. I would keep it simple and make sure you have good backups. This effectively means that you can be up and running again within (at the worst) a small number of hours. Moodle is rarely more critical than that.

You haven't given us any clue about how you are using Moodle (number of users, what they are doing etc.) but my impression is that you are trying to do it with a cluster of very small servers. I can't tell you exactly where the problem lies just that I'm not surprised there is one.

For a proper production site, I would suggest a minimum of 4GB is wise. However, as usual, it depends!

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Re: Moodle Performance Problems (split)

by Pupil Senpro - Tuesday, December 1, 2015, 7:39 PM

I'm still implement just for the server.
For the database and load-balancer I'll think about it later.

Ok, I will try to make 4 GB.
And see the differences.

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Re: Moodle Performance Problems (split)

by Paul Verrall - Tuesday, December 1, 2015, 10:27 PM

RAM might not be your problem. But before we assume it is or isn't how about checking your utilisation and swapping first.

You have a clustered setup, how are you sharing your 'moodledata' folder between them?

I'll take a punt and guess NFS, have you configured your 'localcache' and 'temp' folders to not be on the NFS? Have you put the Moodle code on NFS?

Have you configured your OPCache?

Does memcached have it's own instance, or have you clustered it between your two hosts? You have insanely high allocation btw, I'd be surprised if either cache ever exceeded 64MB. This isn't an issue really as (I think?) memcached does not preallocate, it's just unnecessary.

Then again, maybe it is RAM.

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Re: Moodle Performance Problems (split)

by Pupil Senpro - Wednesday, December 2, 2015, 9:32 AM

Yes, you're right.
I'm added the RAM to 4 GB, but still no luck.

- For "moodledata" folder, I'm sharing it using s3fs.
https://github.com/s3fs-fuse/s3fs-fuse

- For localcache folder, i have put it outside "moodledata" folder. But for temp i haven't make it yet. Here's my "moodledata" content.

My moodledata content

- What is mean by moodle code on NFS? Sorry, forgot to mention I'm a system Engineer and problem related code handled by the Developer.

- I haven't configured the OPcache yet. Anyway, can you elaborate more why I need to configure OPcache?

- For the memcached, It have the own instance. I'm using ElastiCache for the memcached. And 555 MB is the smallest node type.

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Re: Moodle Performance Problems (split)

by Paul Verrall - Wednesday, December 2, 2015, 4:47 PM

I don't know much about s3fs I'm afraid. Looking at https://github.com/s3fs-fuse/s3fs-fuse#limitations I do have some concerns though, specifically, 'no coordination between multiple clients mounting the same bucket'.

I could be misinterpreting this massively, but I think this could be an issue (see https://docs.moodle.org/27/en/Server_cluster#.24CFG-.3Edataroot). While locking shouldn't be an issue for moodledata it will be for 'temp' and 'cache'.

Even if you move these to a more suitable location (cache still needs to be shared with all nodes) I would still look at setting 'preventfilelocking' in your config.php.

My comment regarding 'moodle code on NFS' is better written as 'moodle code should not be on a network file system', it makes things really slow, so each node should have it's own local copy of the codebase.

Opcache is important, see https://docs.moodle.org/30/en/OPcache.

Does ElastiCache give you some stats about your usage? if so I'd over-allocate and then reduce the size once I establish what the real use is (I assume bigger elasticaches cost more $$$).

After all this though Tim is probably most right, networks add latency.

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Re: Moodle Performance Problems (split)

by Pupil Senpro - Wednesday, December 2, 2015, 6:14 PM

Yeah I've thought about it. We suspect that s3fs is the culprit. and we want to try using NFS rather than s3fs. But i haven't try it. Soon I will.

Of course each node should have it's own local copy of the codebase. I don't share them.

Ok, I will give a shot regarding opcache.

Yeah it give some stats, Actually I can see several metric from the CloudWatch. But, i don't know which metrics will matter.

Yeah, Tim probably right. I've just want to improve the performance until there's no can be improve.
Thanks.

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Re: Moodle Performance Problems (split)

by Tim Hunt - Wednesday, December 2, 2015, 12:45 AM

If you have more than one server, then every database query and every cache look-up has to go across the network, which adds latency.

So, multi-server set-ups perform worse when you have only one use accessing the system.

However, they scale better, when multiple users access the system at the same time.

So, that is the trade-off.

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Re: Moodle Performance Problems (split)

by Visvanath Ratnaweera - Wednesday, December 2, 2015, 1:00 AM

Tim, I've heard of a Prof. doing research on super computing by welding sheets of Intel 286es. The point was, his results were useful in designing state-of-art super computers!

May be it is just a story. But I wonder, clustering these clouds, one could prove a point (or two).

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Re: Moodle Performance Problems (split)

by Pupil Senpro - Wednesday, December 2, 2015, 1:26 PM

My post that contains additional information have been marked as spam. Is there any way to recover that post?

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Hardware and performance

Moodle Performance Problems (split)