Another thing that seems to be ignored here is how well gzip performs when
embedding multiple images in a single stylesheet. When we implemented this
feature we were skeptical about possible side-effects of say, embedding the
same image multiple times, or embedding images that might not end up being
used. Our tests showed that gzip was so aggressive at combining common
image headers and in some cases color pallets or actual pixel data, that we
would have to have a pretty extreme situation for these sorts of things to
actually cause performance issues.
- Trevor
On Wed, Sep 25, 2013 at 10:53 PM, Jon Robson <jdlrobson(a)gmail.com> wrote:
Yup very flawed but interesting never the less.
Putting into the back
of the memory bank. Thanks for sharing Ori and thanks Brion for
pointing out the flaws that I also skimmed over :)
On Mon, Sep 23, 2013 at 5:26 PM, Matthew Flaschen
<mflaschen(a)wikimedia.org> wrote:
On 09/23/2013 06:11 PM, Brion Vibber wrote:
Per comments on the article, I wouldn't read much into it -- the
benchmark is pretty flawed. It doesn't measure anything representative
of typical usage.
Yeah. They inexplicably *only* used a single size, a 17.8kB PNG (18227
bytes). If you're not sure why that's a problem, check the size of some
of
the images MW embeds. Examples from a quick
grep:
resources/jquery/images/jquery.arrowSteps.head-ltr.png - 303 bytes
resources/jquery.tipsy/images/tipsy.png - 133 bytes
resources/jquery.ui/themes/vector/images/ui-icons_ffffff_256x240.png -
3702
bytes
resources/mediawiki.action/images/green-checkmark.png - 681 bytes
Why does it matter? The main reason to avoid requests for every single
image is to minimize the time, latency, and bandwidth (bytes) used for
HTTP
request and responses. The smaller the image,
the bigger the fraction
(header size / image size) is, thus the more wasted header time.
What he said about a 814 byte fixed header is also simply wrong. Some of
our data URIs are less than 814 bytes *total*. E.g.
data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAEAAAAkCAAAAABtHw/QAAAAGElEQVQIW2P4wMTA9B8Fo5IIGl0EQQIxAEzaGCA3rKnhAAAAAElFTkSuQmCC
is a real example from jquery.ui.dialog.
We should keep this issue in mind (there is a penalty, particularly for
large images), but that article draws a skewed picture.
Matt
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Jon Robson
http://jonrobson.me.uk
@rakugojon
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