Hello all,

I'm new to Linode and like the system very much, but I'm having some trouble with the speed of my LAMP setup. Many thanks in advance for any help you can provide. Here's my situation:

I copied over my development site from my other VPS (which has less RAM than my Linode) and tried to set it up as similarly as possible. I was able to get it working easily, but immediately noticed that browsing the site on my Linode was very slow. The site is built using Drupal, by the way.

Digging in, I noticed:

* On my front page the Linode required 1,000+ms of SQL queries (compared to 200+ms for the other VPS)

* My front page was rendered generally in 6s, but sometimes as bad as 30s (compared to 2-3s on my old system)

*When loading a page, I never saw CPU usage go above 10%, so I don't think I'm maxing it out ever

* top reveals that I have about 120M free of RAM

* io_status reveals that I have io_tokens=2000000

* To set the server up, I tried out both Fedora Core 6 and Centos 5 distributions (it's what i'm used to). On each one I yum updated everything, yum installed mysql, php, and httpd

* I enabled caching in mysql with query_cache_size=32M - no noticeable improvement

* I enabled APC for php caching - no noticeable improvement

This is a development site - there's no visitors except me and very little load - so I'm not at the stage of fine tuning server performance. I just want it to be reasonably responsive. I was never that happy with the old VPS, so I'm hoping that this can get better. I've tried searching the forums, but I must be missing something.

Googling around, I did notice a few posts that claimed Drupal sites run much better under Xen, so perhaps that's worth a try.

Again, thanks for your help!

I use a few of my linodes to test drupal sites. Performance has been fine for me. Not as fast as a dedi, but still a few secs at most. Turning on caching in drupal can help if you are CPU limited, and if it works for your development needs, but it sounds like you're not.

I can tell sometimes the bandwidth becomes limited, possibly when many other linodes on my host are using bandwidth and we have to share. That might be a possibility for you. For my particular drupal pages, the total size for the generated web content is huge and spread across several resources just for one page, it takes some time to transmit it all.

One possibility is that you're just unlucky and the other Linode users sharing your host are using significant IO and you don't get as much as you used to. The thing about any VPS is that you get unpredictable performance, since it depends on what the other people on your host are doing.

I'm on the Linode xen beta but I don't have drupal running there. Even though linode calls their xen service beta, it has been extremely stable for my uses and noticeably faster. You might try it.

Hi, thanks for your reply.

You're right, I'm not using caching in drupal, since I'm logged in to the site most of the time working on it. When I get it ready for production I'll turn that on, but right now I'm just noticing that it's a bit slow to use for development.

It's quite possible I'm setting something up wrong. MySQL query's are consistently 10x slower than on the other server (as reported by the devel module). I suppose it could just be bad luck that my Linode is overtaxed by other users, as you said, but my dashboard says the load on my Linode is medium, and from what I've read here the io is well enough limited by the io_tokens to keep any one user from hogging it all...

I'll post back if I figure anything out. Let me know if you have any ideas. I'd love to get this working, since otherwise I really like my Linode...

Thanks.

Poor, or no indexing on your tables for the queries you're running?

Need to tune mysql to utilize less memory, to avoid sweeping the disk during large joins or table scans?

EDIT ->> that should read "to utilize MORE memory"

-Chris

Hi Caker,

Thanks for you input.

The indexing on the tables seems fine and is certainly the same on both servers.

mysqld is taking up 13m and the server seems to have plenty of memory free (at least for now, with just me on it so very few apache processes). I don't see any swap activity.

There seems to be a problem both with the speed of MySQL querys and the speed of Apache/PHP execution. On a sample page load, the drupal development tool devel tells me "Executed 280 queries in 2487.21 milliseconds. Page execution time was 33164.62 ms." Both are about 10x off what I expect, though sometimes the page execution is more like 6-10s rather than 30.

Here's vmstat 1 while loading that page:

procs -----------memory---------- ---swap-- -----io---- --system-- -----cpu------
 r  b   swpd   free   buff  cache   si   so    bi    bo   in   cs us sy id wa st
 0  0      0  91904  18112 108500    0    0     2     3  160    9  0  0 100  0  0
 0  0      0  91904  18112 108500    0    0     0     0  109    8  0  0 100  0  0
 2  0      0  92436  18116 107440    0    0     0     0  120   58 20  8 72  0  0
 2  0      0  92436  18116 107520    0    0     0     0  106   11 88 12  0  0  0
 3  0      0  92388  18116 107660    0    0     0     0  118   22 82 18  0  0  0
 2  0      0  92388  18116 107784    0    0     0   644  166   23 50 50  0  0  0
 3  0      0  92264  18116 107932    0    0     0     0  105   19 50 50  0  0  0
 2  0      0  92140  18116 108076    0    0     0     0  131   65 25 75  0  0  0
 3  0      0  92016  18116 108172    0    0     0     0  105   64  0 100  0  0  0
 2  0      0  92016  18116 108200    0    0     0     0  122   39 67 33  0  0  0
 2  0      0  91892  18120 108292    0    0     0   520  143   32 67 33  0  0  0
 2  0      0  91892  18120 108412    0    0     0     0  105   53 50 50  0  0  0
 2  0      0  91644  18120 108556    0    0     0     0  104    4 71 29  0  0  0
 3  0      0  91520  18120 108716    0    0     0     0  123    7 67 33  0  0  0
 3  0      0  91396  18120 108844    0    0     0     0  104    5 67 33  0  0  0
 2  0      0  91188  18124 109048    0    0     0   668  158   13 50 50  0  0  0
 2  0      0  91064  18124 109192    0    0     0     0  107    5 50 50  0  0  0
 2  0      0  90940  18124 109340    0    0     0     0  108    6 38 63  0  0  0
 2  0      0  90816  18124 109492    0    0     0     0  108   72 67 33  0  0  0
 2  0      0  90724  18124 109636    0    0     0   748  126  130 33 67  0  0  0
 2  0      0  90476  18124 109780    0    0     0     0  114  104 44 56  0  0  0
 2  0      0  90352  18124 109916    0    0     0     0  122   91 20 80  0  0  0
 2  0      0  90228  18124 110036    0    0     0     0  109   72 63 38  0  0  0
 3  0      0  90136  18124 110156    0    0     0     0  110   98 50 50  0  0  0
 2  0      0  90012  18124 110336    0    0     0   620  151  141 33 67  0  0  0
 2  0      0  89888  18124 110476    0    0     0     0  108  107 67 33  0  0  0
 1  0      0  89764  18124 110612    0    0     0     0  109   98 38 63  0  0  0
 2  0      0  89640  18124 110748    0    0     0     0  106   93 67 33  0  0  0
 3  0      0  89392  18124 110936    0    0     0   688  153  146 80 20  0  0  0
 2  0      0  89284  18124 111076    0    0     0     0  110   25 43 57  0  0  0
 2  0      0  88392  18124 111208    0    0     0     0  118   21 80 20  0  0  0
 2  0      0  87772  18124 111344    0    0     0   508  117   44 33 67  0  0  0
 2  0      0  87772  18128 111456    0    0     0   184  120   12 40 60  0  0  0
 2  0      0  87524  18136 111572    0    0     0     0  116    6 33 67  0  0  0
 3  0      0  87400  18136 111696    0    0     0     0  138    4 50 50  0  0  0
 4  0      0  87152  18136 111816    0    0     0     0  121    5 50 50  0  0  0
 3  0      0  86904  18136 111960    0    0     0   228  163    7 38 63  0  0  0
 2  0      0  86680  18136 112092    0    0     0   564  118    7 60 40  0  0  0
 3  0      0  86432  18136 112228    0    0     0     0  120    4 33 67  0  0  0
 2  0      0  86184  18136 112348    0    0     0     0  113    5 33 67  0  0  0
 2  0      0  85936  18136 112500    0    0     0     4  124   11 50 50  0  0  0
 1  0      0  85564  18136 112776    0    0     0   652  140   14 75 25  0  0  0
 1  0      0  85580  18136 112776    0    0     0     0  123   31  4  0 96  0  0
 1  0      0  85580  18136 112780    0    0     0     0  124   38  2  0 98  0  0
 0  0      0  85580  18136 112780    0    0     0     0  103    8  0  0 100  0  0
 0  0      0  85580  18136 112780    0    0     0    28  106   10  0  0 100  0  0
 0  0      0  85580  18136 112780    0    0     0     0  102    8  0  0 100  0  0
 0  0      0  85580  18136 112780    0    0     0     0  102    5  0  0 100  0  0

Your vmstat output shows that it's CPU bound. Something seems odd here.

Anyway ... Have you given any thought to registering for the Xen beta? The Xen boxes are stable and have much less overhead (plus 4 processor cores in the Linodes instead of just 1).

-Chris