Re: Failed to hand off onionskin

[Scott Bennett <bennett@xxxxxxxxxx>]

     On Tue, 16 Dec 2008 18:44:58 -0500 Roger Dingledine <arma@xxxxxxx>
wrote:
>On Wed, Dec 17, 2008 at 12:28:37AM +0100, Mitar wrote:
>> From time to time I am getting this warning:
>> 
>> Failed to hand off onionskin. Closing.
>> Your computer is too slow to handle this many circuit creation
>> requests! Please consider using the MaxAdvertisedBandwidth config
>> option or choosing a more restricted exit policy.
>
>This warning happens when you have more than 100 create cells queued
>for processing, so presumably your CPU isn't able to keep up with them.
>
>> I have been monitoring the system and while it is true that sometimes
>> it tops one processor, it occupies most of the time just 50 % of one
>> processor. I have also configured Tor daemon to use two threads so
>> even if it tops one it could still switch to another. But it rarely
>> passes 100 % (that is, it rarely really uses two processors). The
>> system as a whole has also not topped its CPU power. And while load
>> does not seem to be so high I get at the same time this errors. Is
>> there some other system bound which would be causing this and not CPU?
>> Are there some other performance tweaks I could try?
>
>Well, step one is to set
>NumCPUs 2
>but I think you already did that.
>
     Roger missed mentioning (step two) that you can adjust the queue limit
yourself, e.g., by adding to torrc

MaxONionsPending 200

to double the default limit of 100.  Try 200, and if that takes care of it,
fine.  If not, set it to something higher.  It does increase tor's memory
requirement, but only by a small amount.


                                  Scott Bennett, Comm. ASMELG, CFIAG
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