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uTorrent causes my RAM usage to skyrocket


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Here's the problem. It happens on big torrents only (e.g. a linux ISO file). As the download progresses, my free RAM goes down from ~500MB to 3-4MB (yes), accompanied with a horrible slowdown of windows. At that point the hard disk does something and I get ~80MB free, then it goes down to 0 again. If I stop the torrent, the RAM returns in ~30 seconds (as in, I suddenly get ~400MB of free RAM). The task manager shows no abnormal memory usage by utorrent.exe, or any other process. This happens with the latest official build (1.6.1) and the latest beta. In my experience, BitComet doesn't have this problem, but I think it's because it bypasses the Windows file cache. My understanding (from several posts on these forums) is that this is the fault of the Windows file cache. So are there any plans to fix that? I understand that it's not the programmers' fault, but when you boast of having the leanest and meanest torrent client, such RAM usage is a no-no and a workaround is necessary. I would like to continue using uTorrent, but this bug (for lack of a better word) is a showstopper.

I'm using XP Professional, fully updated, tcpip.sys patched for max halfopen connections, and am not running any of the conflicting software listed in the FAQ.

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The beta I have now is 1355, and I've used at least 3 betas of 1.7 before that. Like I said, it also happens in 1.6.1. Cache settings - I've tried setting it to several values, as well as leaving it automatic. I am not running any resident antispyware, antivirus is NOD32, and I don't use a firewall (the default XP is disabled).

edit: NOD32's IMON module is disabled, so it can't be that.

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This behavior is known (memory usage increasing without any culprit, only occuring when µTorrent is running) and has been more-or-less determined to be the Windows cache being stupid. AFAIK, any amount of tweaking to the disk cache won't help, as µTorrent's disk cache actually shows up as increased memory usage by µTorrent (at least it's failed to help anyone with this problem to mess with cache settings before).

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  • 3 weeks later...


I have Windows XP x64 Edition + uTorrent 1.7 beta 1952, and I have the same problem.

My physical memory size is 2Gb.

While downloading a 4GB file - windows system disk cache goes well beyond 1GB.

I wonder, why does uTorrent use windows file caching at all when it has a caching system of its own??

One cache is always better than two.

Just open the file with caching disabled and the problem would probably be gone.

Am I not right?

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I think, this problem must be solvable.

AFAIK, the only limitation of non-system-cached files is that they must be read in sector-aligned blocks. This limitation should be easy to overcome.

So, the problem left is that uTorrent cache is not efficient enough...

Is it really THAT inefficient?

Anyway, i better suffer a bit slower download/upload speeds than to give my ENTIRE RAM to the system cache. :)

Should I start a new topic in the feature request forum?

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I also get "disk overload 100%?" message! I've increased cache to 200Mb but after 1/2 hour the message reappears and the cache is full! It seems that no matter how much cache size i set is not enough! BTW: 'Increase automatic cache size' is checked! I reinstalled 1.6.1 version and the message is there! I use Avast and Windows firewall! I've unchecked all cache advanced settings and now it seems that utorrent is working properly! utorrent version is 1839 i believe(!not sure but 18xx is sure)

Latest update:

It seems that in 2151 release cache is working properly(size is normal).

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The amount of memory used for system cache seems to be different on different versions of Windows (maybe RAM size matters as well), independent on version of uTorrent.

I had the problem with 1.6.1, and have the same problem with 1.7 beta now.

On one machine (Windows XP Professional, 1GB RAM) - system cache grows to a few hundred MBytes and stops there.

On the second machine (Windows XP Professional x64 Edition, 2GB RAM) - system cache growth seems to be unlimited. (Grows almost to 2GB)

On the second (x64) machine the effect is terrible! After the download of a big file - every program resides in the swap-file, and everything is terribly slow.

On the first machine (x86) the effect is not so extreme, but a few hundred megabytes of RAM is not something you can just ignore.

IMHO, system caching of the files being downloaded/uploaded is completely unnecessary.

Firon, try to monitor system cache size with the Performance Monitor (the counter "Memory/Cache Bytes").


If it matters - i download/upload at the speed of about 2-5MBytes/s.

System cache does not go to 2GB instantly, but raises slowly, as the download/upload progresses.

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