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I'm currently running Firefox 34.0 and Chrome 39.0 on Ubuntu 14.04.
Firefox is presenting with extremely slow DNS look-ups that aren't occurring in Chrome. In order to repro, I've shut down both Ffox and Chrome, and opened new windows. I then visit a new domain that I haven't yet visited, first in Ffox, then Chrome. In order to make sure it's not caching causing the difference, I then try a different domain first with Chrome, and then with Ffox. I repeated this a number of times to make sure.
When visiting a new domain for the first time with Ffox, I see the "Looking up domainname" dialog, and it takes roughly 10 seconds in order to complete the page load, mostly due to what seems to an extremely slow DNS lookup. I'm having no such issues in Chrome.
Additionally, after the first time I visit a website in Ffox, future pageloads are snappy, presumably due to some sort of caching. However, closing Ffox and opening it again will seemingly clear that cache.
I have tried a couple of things here and here, though neither has resolved the issue.
I feel as though it would be very useful to see the requests that Ffox is making in order to understand what's going on, but I've never done that sort of thing before. What would be some useful tools/and how would I use them to diagnose a problem like this?
Justin
Posted 2014-12-26T09:01:44.010
Reputation: 123
In order to compare, open an empty window. Then run `firefox http://domain.com". Chrome will preload before you press enter.
– davidbaumann – 2014-12-26T09:27:35.827https://chrome.google.com/webstore/detail/page-load-time/fploionmjgeclbkemipmkogoaohcdbig http://getfirebug.com/ – davidbaumann – 2014-12-26T09:28:48.987
If you visit a website for a domain in Firefox first and then visit it with Chrome, you haven't eliminated the possibility that DNS caching is playing a role. When you visited it in Firefox, the IP address is stored in the operating system's DNS cache, which means Chrome can retrieve it from that cache. You could use
– moonpoint – 2015-07-25T14:49:41.080sudo /etc/init.d/nscd restartto flush that cache in Ubuntu - see How to flush dns in ubuntu 12.04?Even clearing the DNS cache on your Ubuntu system hasn't eliminated any possible caching-related issue. Because if the DNS server your system queried didn't have the domain to IP address mapping before, it now has it when your system queried it for that domain's IP address. That DNS server will retain the information based on the TTL value for the DNS record in whatever other DNS server is authoritative for that domain. Granted, that probably isn't a factor in this case, but still the role of caching can, potentially, be a factor.
– moonpoint – 2015-07-25T14:58:33.680