Driver porting: Zero-copy user-space access

Driver porting: Zero-copy user-space access

Posted Sep 6, 2007 15:28 UTC (Thu) by dnevil (guest, #47212)
In reply to: Driver porting: Zero-copy user-space access by ceb
Parent article: Driver porting: Zero-copy user-space access

Sounds like your system is allocating memory from ZONE_HIGHMEM (since you are on a heavily loaded system, and you are probably running i386). The comments in include/linux/mm_types states that if page->virtual is null then the page is not mapped into kernel virtual memory (i.e. it is HIGHMEM). You should try allocating your memory as soon after system boot as possible. Are there other 'tricks' for assuring that user-allocated memory comes from ZONE_NORMAL or ZONE_DMA?

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