When I run ktorrent with 5 downloads, one core of my CPU is running on 100%. When I look at process table ktorrent process shows either 4 or 5 % CPU usage or disk sleep. Network history shows that data is downloaded only by few seconds then there is a longer quiet period, again few seconds interval of downloading and brake again.  When I kill ktorrent the core that was running at 100% slows down to 3-2%. Moreover when I try to open help or settings  in menu bar, not only ktorrent but all system becomes unresponsive.  

Reproducible: Always

Steps to Reproduce:
1. Launch ktorrent with few downloads
2.
3.

Actual Results:  
Downloading only in short time intervals, high cpu usage 

Expected Results:  
continuous downloading, lower cpu usage

I disabled akonadi, here is lspci output:

00:00.0 Host bridge: Intel Corporation 3rd Gen Core processor DRAM Controller (rev 09)
00:02.0 VGA compatible controller: Intel Corporation 3rd Gen Core processor Graphics Controller (rev 09)
00:14.0 USB controller: Intel Corporation 7 Series/C210 Series Chipset Family USB xHCI Host Controller (rev 04)
00:16.0 Communication controller: Intel Corporation 7 Series/C210 Series Chipset Family MEI Controller #1 (rev 04)
00:1a.0 USB controller: Intel Corporation 7 Series/C210 Series Chipset Family USB Enhanced Host Controller #2 (rev 04)
00:1b.0 Audio device: Intel Corporation 7 Series/C210 Series Chipset Family High Definition Audio Controller (rev 04)
00:1c.0 PCI bridge: Intel Corporation 7 Series/C210 Series Chipset Family PCI Express Root Port 1 (rev c4)
00:1c.3 PCI bridge: Intel Corporation 7 Series/C210 Series Chipset Family PCI Express Root Port 4 (rev c4)
00:1d.0 USB controller: Intel Corporation 7 Series/C210 Series Chipset Family USB Enhanced Host Controller #1 (rev 04)
00:1f.0 ISA bridge: Intel Corporation HM77 Express Chipset LPC Controller (rev 04)
00:1f.2 SATA controller: Intel Corporation 7 Series Chipset Family 6-port SATA Controller [AHCI mode] (rev 04)
00:1f.3 SMBus: Intel Corporation 7 Series/C210 Series Chipset Family SMBus Controller (rev 04)
02:00.0 Network controller: Qualcomm Atheros AR9462 Wireless Network Adapter (rev 01)