Hi, So currently the TTM interface allows the user specify a cacheable allocation, and on Intel hardware this gets conflated with using the intel snooped memory type in the GART. This is bad as the intel snooped memory type comes with its own set of special rules and sucks for lots of things.
However I want to be able to use the cacheable CPU memory with the GPU to a) make things go fast b) avoid lots of SMP cross-talking and cache flushing (see a) c) buffer object creation faster So this led me to the patch at: http://cgit.freedesktop.org/~airlied/drm/diff/?h=intel-hackery&id=da14a0bbb8849cdc91ca87786fde90ac36fe1198 I could add back the snooped option if we want using a driver private flag. This patch evicts the buffer on mapping so the GPU doesn't see anything via the aperture or otherwise, and flushes before validating into the aperture. It doesn't contain the chipset flush patch yet which is requried to actually make it work (add agp_chipset_flush to i915_dma.c before submitting the batchbuffer) This works and appears to be nice and fast, all userspace buffers can be allocated _LOCAL | _CACHED and validated to _TT later without any major cache flushing overhead when we have clflush, and without SMP overhead at all as cache flushing is cache coherent on the Intel chipsets I've played with so far (CPU coherent- not GPU) I of course need to makes this code not so x86 specific, so I might add a page flush hook to the driver interface and put the flushing code in the driver side. This also leads me into backwards compatibility, the chipset flushing changes to AGP are required for all of this good stuff, options are 1) resurrect linux-agp-compat add chipset flushing code - easier 2) try and hack chipset flushing into drm_compat.c - probably more difficult that I would like to bother with.. So comments please on whether a comeback for linux-agp-compat is a good or bad thing.. Dave. -- David Airlie, Software Engineer http://www.skynet.ie/~airlied / airlied at skynet.ie Linux kernel - DRI, VAX / pam_smb / ILUG ------------------------------------------------------------------------- This SF.net email is sponsored by: Splunk Inc. Still grepping through log files to find problems? Stop. Now Search log events and configuration files using AJAX and a browser. Download your FREE copy of Splunk now >> http://get.splunk.com/ -- _______________________________________________ Dri-devel mailing list Dri-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/dri-devel
