On 8/9/2015 6:19 PM, Chris Wilson wrote:
On Sun, Aug 09, 2015 at 05:11:52PM +0530, Goel, Akash wrote:
On 8/9/2015 4:25 PM, Chris Wilson wrote:
On Sun, Aug 09, 2015 at 04:23:01PM +0530, Goel, Akash wrote:
On 8/7/2015 1:37 PM, Daniel Vetter wrote:
I presume though you only want to avoid clflush when actually purging an
object, so maybe we can keep this by purging the shmem backing node first
and checking here for __I915_MADV_PURGED instead?
An object marked as MADV_DONT_NEED, implies that it will be
purged/truncated right away after the call to put_pages_gtt
function.
So doing the other way round by purging first and then checking for
__I915_MADV_PURGED, might be equivalent.
But disregards a few nice sanity checks, which I would like to keep.
-Chris
Fine, just wanted to convey that doing the other way round may not
be really beneficial.
About the other point of virtually indexed/physically tagged cache,
would it be safe just rely on the MADV_DONT_NEED state of the object
(which indicates that there are no active CPU mmappings) ?
Due to an earlier CPU mmappings, there could be cachelines holding
the stale data ?
If the conflicts survive munmap(), I don't have a clever idea on how to
avoid the clflush before we hand back the pages to the system.
One case could be, as you suggested, check if ever there was a CPU
mapping created for the object & so avoid the clflush for GPU (GPU +
GTT) only objects.
Best regards
Akash
-Chris
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