988488 - High CPU usage when downloading files

Status: RESOLVED DUPLICATE of bug 902733

(Firefox :: Untriaged, defect)

Description

[nicholas.jakobsen]

Attachment: Screen Shot 2014-03-26 at 11.36.32 AM.png

User Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_9_2) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/33.0.1750.152 Safari/537.36

Steps to reproduce:

Download a file, (I was downloading SQL Server, ~3gb). Close all tabs.


Actual results:

Downloading at ~2.4MB/s  Firefox CPU usage spikes to ~30%
Downloading at ~3MB/s  Firefox CPU usage spikes to ~40%


Expected results:

CPU usage shouldn't spike so high.

Comment 1

[nicholas.jakobsen]

When the download completes, Firefox CPU usage drops to 0%.

Comment 2

[[:Aleksej]]

Downloading at 4+ MB/s, no usage over 20% (a nettop).
firefox-28.0.en-US.linux64

Comment 3

[YF (Yang)]

Could you try http://support.mozilla.com/en-US/kb/Safe+Mode

and try removing the downloads button from the toolbar and rewatch, by bug 888129.

Comment 4

[tpdi]

I'm seeing the same issue, with a file of unknown size and only when the down list is open (displayed). 

Interestingly, both Firefox *and* Intel's Zero Config Service show CPU spikes, *each* around 20%.

The CPU usage returns to normal levels when the download list is hidden.

Comment 5

[tpdi]

Attachment: ff-high-cpu-while-download-list-is-open--before.png

Comment 6

[tpdi]

Attachment: ff-high-cpu-while-download-list-is-open--during.png

Comment 7

[tpdi]

Attachment: ff-high-cpu-while-download-list-is-open--after.png

Comment 8

[Kai-Uwe Rommel]

I also see the problem of high CPU usage when downloading some large files with sufficient download rate (e.g. 1 MByte/sec or higher) - always, reproducible and on each and every Firefox installation that I use (all on Windows).

For example, I just downloaded both a RHEL and a CentOS ISO image at the same time. Combined both downloads had a throughput of about 6...8 MByte/sec. Firefox' CPU usage went to 70% on a VM using two Xeon server cores. When one download finished and I unpacked that ISO with 7Zip, the 7Z process used almost NO CPU at all while Firefox still used more than 50%.

So, something is really programmed in a bad way in the Firefox download code. I am seeing this, as I already wrote, on many installations and always and since so many years of using Firefox that I am very astonished that it should not be reproducible by the developers so that it could be fixed quickly.

Comment 9

[Dmitry Gutov]

When downloading a file (e.g. Kubuntu ISO from its official site, at ~1.4MB/s), the CPU usage hovers around 20%. And it drops to under 5% as soon as I cancel the download. qBittorrent, as a point of comparison, never goes above 10%, even though it's doing more CPU intensive stuff along with downloading.

Whether the "downloads" button is on the toolbar or hidden, doesn't seem to make a lot of difference (it seemed to add a few percent, but I can't say for sure, with the percentage floating around).

The effect is stable, and happens with an empty profile I've set up for testing.

Ubuntu 15.10, Firefox 44.0a2 (2015-11-20).

Comment 10

[Karl Tomlinson (:karlt)]

The download list issue of comment 4 sounds a little different from what others are seeing even without the list open, and so may be worth filing separately.

Removing the download button from the toolbar resolves the problem.

Comment 11

[Karl Tomlinson (:karlt)]

(In reply to Karl Tomlinson (ni?:karlt) from comment #10)
> The download list issue of comment 4 sounds a little different from what
> others are seeing even without the list open

Bug 1053840 may cover that.