I haven't been able to find STR on this, but I regularly find that Fennec spins my phone (Galaxy Nexus)'s CPU, making interaction (panning and zooming) very slow - think 1-2 fps - and my phone gradually gets hot. This is a fairly content-free bug, but I want it on file because it's a very bad problem when it happens.

If it matters, I'm using Sync.

I have now had this happen twice on this CNN URL. Let the page load fully, including the comments.

When I'm seeing this, I get a stream of things like D/BrowserRepoSession( 6638): Adding visits for GUID IIWPucBeSlE7 D/BrowserDataAccessor( 6638): Storing visits for IIWPucBeSlE7, replacing IIWPucBeSlE7 D/BrowserRepoSession( 6638): Adding visits for GUID Iea3p_lb1RGT D/BrowserDataAccessor( 6638): Storing visits for Iea3p_lb1RGT, replacing Iea3p_lb1RGT After a little while on this site, the problem seems to go away. I choose Ally!

Yup, it's syncing. I expect you're adding a lot of history on desktop, so it's doing non-trivial work when it syncs on the phone. The particular site shouldn't matter; Sync will run even when Fennec is not, so you're probably just noticing more in this case. If you get a chance, logcat with time output captured during or after a slow period would help: http://160.twinql.com/how-to-file-a-good-android-sync-bug Thanks!

assigning to joe (and mfinkle) for gathering more information

I had this sync happen while I was using Fennec: http://pastebin.mozilla.org/1528382 I then forced a sync at Richard's request: http://pastebin.mozilla.org/1528333 Are these of any help?