Pages with large number of thumbnails tends to be a
slow path in the
parser. This is even more true for people using instant commons. I dont
know for sure, but I imagine it could be improved by batching the checks
for finding image width/height (that might be a difficult change to make
though).
Batching requests sounds possible but would need to retool some things. The
good news is the file links should all be visible in the expanded
preprocessor DOM, so it should be possible to walk the tree, make a
list, batch the file lookup requests and then pass the batch cache into the
Linker functions.
Uh, that's assuming I'm not misremembering the order of operations with
respect to template expansion. :)
IIRC, InstantCommons is slightly trickier as you also need to make multiple
API calls to fetch thumbnail URLs, made even worse by needing to fetch
multiple resolutions for srcset. This gets real nasty if there are a lot of
files and the thumbnail ref data isn't cached...
We could change all that if there was a stable enough URL/linking
API... Can probably fake it for common cases and supported handlers by
generating a URL like we would for a local 404-handler repo; my main
concern is for future expansion where we add more fancy types on Commons
where the local site may not have an extension installed locally. (Iframe
embedding as a fallback for unknown handlers sounds possible, could expose
a frame URL in the imageinfo data.)
-- brion
--
Bawolff
On Saturday, May 28, 2016, Pine W <wiki.pine(a)gmail.com <javascript:;>>
wrote:
Thank you for the update. FWIW, a page that I
load frequently that takes
a
long time is Commons' featured picture
candidates. My guess is that
starting with the implementation of HHVM and with smaller improvements
thereafter, the page load time had been reduced by more than 50%, which
is
impressive and much appreciated.
Pine
On May 27, 2016 15:28, "Ori Livneh" <ori(a)wikimedia.org
<javascript:;>>
wrote:
> Hello,
>
> Here's what the performance team has been up to.
>
> == Dashboards & instrumentation ==
> We spent time instrumenting software and curating displays of
performance
> data. We have several new dashboards to share
with you:
>
> * Global edit rate and save failures (new)
>
https://grafana.wikimedia.org/dashboard/db/edit-count
>
> * Performance metrics (revamped)
>
https://grafana-admin.wikimedia.org/dashboard/db/performance-metrics
>
> * Page load performance
>
https://grafana.wikimedia.org/dashboard/db/navigation-timing
>
> ...by continent:
>
https://grafana.wikimedia.org/dashboard/db/navigation-timing-by-continent
> ...by country :
>
https://grafana.wikimedia.org/dashboard/db/navigation-timing-by-geolocation
> ...by browser :
>
https://grafana.wikimedia.org/dashboard/db/navigation-timing-by-browser
>
> * We found that certain browsers were reporting wildly inaccurate timing
> data and skewing our summary performance metrics, and reacted by
validating
> browser metric data more strictly against
Navigation Timing API specs.
>
>
> == ResourceLoader ==
> ResourceLoader is the MediaWiki subsystem responsible for loading CSS,
> JavaScript, and i18n interface messages for dynamic site features. It is
> critical to site performance. Changes to ResourceLoader are focused on
> reducing backend response time, ensuring we make efficient use of the
> browser cache, and reducing time to first paint (the time it takes any
> content to appear). This work is led by Timo Tijhof.
>
> * The "/static/$mwBranch" entry point has been deprecated and removed in
> favor of wmfstatic - a new multiversion-powered entrypoint accessed via
> "/w" (via RewriteRule)
>
https://phabricator.wikimedia.org/T99096
>
> * Restricting addModuleStyles() to style-only modules (ongoing)
>
https://phabricator.wikimedia.org/T92459
>
> * Startup module check is now based on a feature test instead of browser
> blacklist
>
https://phabricator.wikimedia.org/T102318
>
>
> == WebPageTest ==
> Page load performance varies by browser, platform, and network. To
> anticipate how code changes will impact page performance for readers and
> editors, we use WebPageTest (
>
https://wikitech.wikimedia.org/wiki/WebPageTest),
> a web performance browser automation tool. WebPageTest loads pages on
> Wikimedia wikis using real browsers and collects timing metrics. This
work
> is led by Peter Hedenskog.
>
> * We now generate waterfall charts for page loads on Firefox. Previously
we
> were only able to produce them with Chrome.
>
> * We tracked downs two bugs in WebPageTest that caused it to report an
> incorrect value for time-to-first-byte and reported them upstream.
>
https://phabricator.wikimedia.org/T130182
>
https://phabricator.wikimedia.org/T129735
>
> * We upgraded the WebPageTest agent instance after observing variability
in
> measurements when the agent is under load.
>
https://phabricator.wikimedia.org/T135985
>
> * We designed a new dashboard to help us spot performance regressions
>
https://grafana.wikimedia.org/dashboard/db/webpagetest
>
>
> == Databases ==
> The major effort in backend performance has been to reduce replication
lag.
> Replication lag occurs when a slave database
is not able to reflect
changes
> on the master database quickly enough and
falls behind. Aaron Schulz set
> out to bring peak replication lag down from ten seconds to below five,
by
> identifying problematic query patterns and
rewriting them to be more
> efficient. We are very close to hitting that target: replication lag is
> almost entirely below five seconds on all clusters.
>
>
https://phabricator.wikimedia.org/T95501
>
> * High lag on databases used to generate special pages no longer stops
job
> queue processing
>
https://phabricator.wikimedia.org/T135809
>
> == Multi-DC ==
> "Multi-DC" refers to ongoing work to make it possible to serve reads
from a
> secondary data center. Having MediaWiki
running and serving requests in
> more than one data center will reduce latency and improve site
reliability.
> This project is led by Aaron Schulz.
>
> In order for this to be possible, we need to be able to anticipate which
> requests will need the master database, so we can route them
accordingly.
> The plan is to achieve this by making sure
that GET requests never
require
> a master database connection. We've made
progress incremental progress
> here, most recently by changing action=rollback to use JavaScript to
> perform HTTP POST requests.
>
> We also need to be able to broadcast cache purges across data centers.
The
> major work on this front has been the
addition to core of EventBus
classes
> that relay cache proxy and object cache
purges. Stas Malyshev of the
> discovery team is assisting with this work.
>
> == Thumbor ==
> "Thumbor" is shorthand for the project to factor thumbnail rendering out
of
> MediaWiki and into a standalone service based
on Thumbor (
>
http://thumbor.org/). This project is led by Gilles Dubuc. The
following
> list summarizes recent progress:
>
> - Simplified the VCL as much as possible
> - Added client throttling with the tbf vmod
> - Added progressive JPEG support to ImageMagick engine
> - Added configurable chroma subsampling support
> - Made SVG detection more robust
> - Added multilanguage SVG support
> - Reproduced temp folder security mechanism found in MediaWiki for SVG
for
> all file types
> - Swift's rewrite.py ported to vagrant. On Vagrant thumbor now hooks
itself
> into the same point in the stack it will in
production
> - Swift storage implemented (shard support left to do)
> - Matched Content-Disposition behavior to MediaWiki
> - Vastly increased performance on JPEG processing by using a
long-running
> exiftool process and named pipes to pass
commands to it
> - Made one instance of thumbor run on each available core on vagrant,
since
thumbor
is single-threaded
- Debian packaging well under way:
https://phabricator.wikimedia.org/T134485
all dependencies covered except one. 14 backports and 17 new packages so
far. Working with Filippo to get as many of these into Debian proper as
possible.
Until next time,
Aaron, Gilles, Ori, Timo, and Peter
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