[PATCH RFC]: Bus_dma eats all available memory

Scott Long scottl at samsco.org
Thu Jun 25 18:30:37 UTC 2009

Piotr Zięcik wrote:
> Hi
> While working on new driver for FreeBSD I have found a problem in bus_dma 
> subsystem. Every time when bus_dmamap_create() is called on bus_dma tag
> using bounce zone, at least 1 page in bounce zone is allocated. This causes 
> eating of all avaible memory by bounce zone. Problem affects i386, amd64 and 
> arm.

The code block that you point at can only be entered if the maxpages 
limit has not been reached.  However, the max limit is per zone, not
global, and there's no easy way to make it be global.  Are you creating
an excessive number of tags/zones?


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