Re: can't access video memory?
From: Jon Smirl <hidden>
Date: 2005-09-10 15:01:51
On 9/10/05, fbui@comcast.net [off-list ref] wrote:
quoted
Zack Smith wrote:quoted
Does anyone know what might cause this?
On x86 the kernel is limited to 1GB of virtual address space. So physical memory plus mapped video needs to total less than 1GB for best performance. Systems with 1GB of RAM or more want to minimize mapped VRAM. Anything that is mapped over the minimum pushes kernel data structures out of normal access and into highmem access which is significantly slower. For example mapping a 512MB video card on a 1GB system knocks about 10% off from your system performance since it pushes 512MB of RAM into highmem access mode. The drivers aren't smart enough to look for less than 1GB of physical memory and expand their mapped areas. None of this applies from user space. There are no problems with mapping the full card. -- Jon Smirl jonsmirl@gmail.com ------------------------------------------------------- SF.Net email is Sponsored by the Better Software Conference & EXPO September 19-22, 2005 * San Francisco, CA * Development Lifecycle Practices Agile & Plan-Driven Development * Managing Projects & Teams * Testing & QA Security * Process Improvement & Measurement * http://www.sqe.com/bsce5sf