Tag: performance

Northern Quarter Open Mic: Ethan

So I went to the Open Mic night at the Northern Quarter bar in Huddersfield last week for the first time and saw an act that was quite upsetting. Turned out to be just a guy doing his act but at the time I was actually kind of terrified. A unique experience. Meet Ethan.

Ethan is a gaunt, serious looking chap, wearing glasses, a long dark coat and a baseball cap. He keeps popping out for smokes all evening and generally seemed a bit jittery. Towards the end of the night he gets called up on stage.

His first song is a slow spoken word cover of “Fever” over a strange noisy electronic backing track, during which he paces nervously around the small stage. For his second song, he kneels down behind a small duffel bag, holding it open towards himself and staring into it.

Through the largish PA system blares an oppressively loud droning noisy low note. His words are distorted by the bass but from what I can make out this is a desperate man unable to care for his family, reaching the end of his tether. He’s been staring into his bag the whole time.

And suddenly I think: has this guy got a gun in his bag and is he going to shoot himself? The loud bass line is upsetting enough, booming against my chest, but now I’m actually a bit concerned. I’m near the open door and I start kind of planning an exit! My heart is racing!

The noise builds and builds and I’m wondering if I’m going to have a panic attack. Then at the peak, he quickly reaches into the bag and pulls out a white papier-mâché mask/helmet, puts it on his head and starts writhing around on the floor.

So Ethan is obviously a genius. But I think the fact I’ve never seen him before, so didn’t know what to expect, and that I was already nervous myself from having performed earlier meant his act landed just “perfectly” and I was quite terrified.

I spoke to him after and excitedly told him my experience but he barely allowed himself a smile. Was I ruining it by acknowledging it? Or was I just the weird one?

12/4/2022 Add Comment

Netfilter Conntrack Memory Usage

On a busy Linux Netfilter-based firewall, you usually need to up the maximum number of allowed tracked connections (or new connections will be denied and you’ll see log messages from the kernel link this: nf_conntrack: table full, dropping packet.

More connections will use more RAM, but how much?  We don’t want to overcommit, as the connection tracker uses unswappable memory and things will blow up. If we set aside 512MB for connection tracking, how many concurrent connections can we track?

There is some Netfilter documentation on wallfire.org, but it’s quite old. How can we be sure it’s still correct without completely understanding the Netfilter code? Does it account for real life constraints such as page size, or is it just derived from looking at the code? A running Linux kernel gives us all the info we need through it’s slabinfo proc file.
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17/6/2009 4 Comments

My Ukepedia Talk at Barcamp Leeds 2009

Tim Dobson very kindly recorded and uploaded my talk on the Ukepedia at Barcamp Leeds last Saturday.

For those of your with short attention spans, I finally get started with the talk at about 2mins 30, and start singing the first article, Otitis Media, at about 7mins.

5/6/2009 Add Comment

High performance WordPress

Of all the WordPress installations I manage, two of them bring in a rather large number of hits.

To speed up WordPress I usually just enable the MySQL query cache and install the eaccelerator PHP opcode cacher. On one particular box, an Intel 1.3Ghgz PIII this increased performance from around 3 requests per second to around 10.

Recently I came across the WP-Cache plugin for WordPress. This takes the finished output from any given wordpress request and caches it to disk, serving directly from the static cache for the next hour (configurable). Any new posts or comments in the mean time immediately mark the cached version stale, so you don’t need to wait around for an hour.

On the same hardware and blog, this increases performance from 10 requests per second to over 250. A 2500% increase in speed.
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5/6/2006 Add Comment

Lighttpd and Ruby on Rails: Secure and Fast Downloading

When controlling access to files on a webserver developers often use the web application itself as a file server. The request comes in, the script checks for some session authentication variable or something, then streams the file from disk (hopefully from outside the webroot) to the browser.

The problem with this from a performance standpoint is that a thread/process of the web application has to be running for the entire duration of the download. With a busy webserver serving many concurrent downloads, this is an immense overhead. The web server itself should be orders of magnitude faster at serving files directly than via a web application, but you can’t just stick the files in a different directory and hope nobody finds the secret urls. The new web server on the block, Lighttpd, has some clever solutions for this problem.
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16/3/2006 3 Comments

eAccelerator php speederupper

My earlier post about Turck-mmcache is now deprecated. Turck-mmcache has not been actively developed in quite a while. eAccelerator is a fork of Turck-mmcache and has been actively developed by a new team.

eAccelerator fixes all the PHP crashing errors I had, and adds support for newer version PHP too (including PHP 5.1 in their latest dev snapshot, which I’ve had working perfectly btw)

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15/1/2006 Add Comment