<div dir="ltr"><div class="gmail_extra"><div class="gmail_quote">On Fri, Dec 15, 2017 at 8:27 AM, Chris Wilson <<a href="mailto:chris@chris-wilson.co.uk" target="_blank">chris@chris-wilson.co.uk</a>> wrote: <blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Quoting Jason Ekstrand (2017-12-15 16:21:42) <div><div class="h5">> On Fri, Dec 15, 2017 at 5:42 AM, Chris Wilson <<a href="mailto:chris@chris-wilson.co.uk">chris@chris-wilson.co.uk</a>> wrote: > > Every client (everyone instance that opens /dev/dri/card0 or the render > nodes), receives a unique per-process GTT (where supported by the > hardware, unfortunately that means only Broadwell and later). Every > context created by each client, in turns receives its own unique ppGTT. > This is overkill in terms of allocations and tracking, both in the > kernel and in the hardware, as we could be sharing the per-client GTT > amongst all of its contexts. The downside is that context segregation is > reduced, a stray write from one context may affect another, and so we > must honour any client requests that require robust segregation (e.g. > ARB_robustness). > > Signed-off-by: Chris Wilson <<a href="mailto:chris@chris-wilson.co.uk">chris@chris-wilson.co.uk</a>> > --- > src/mesa/drivers/dri/i965/brw_bufmgr.c | 23 +++++++++++++++++------ > src/mesa/drivers/dri/i965/brw_bufmgr.h | 2 +- > src/mesa/drivers/dri/i965/brw_context.c | 2 +- > 3 files changed, 19 insertions(+), 8 deletions(-) > > diff --git a/src/mesa/drivers/dri/i965/brw_bufmgr.c b/src/mesa/drivers/dri/ > i965/brw_bufmgr.c > index 52b5bf97a1..d8a9635f5d 100644 > --- a/src/mesa/drivers/dri/i965/brw_bufmgr.c > +++ b/src/mesa/drivers/dri/i965/brw_bufmgr.c > @@ -1297,13 +1297,24 @@ init_cache_buckets(struct brw_bufmgr *bufmgr) > } > > uint32_t > -brw_create_hw_context(struct brw_bufmgr *bufmgr) > +brw_create_hw_context(struct brw_bufmgr *bufmgr, unsigned int flags) > { > - struct drm_i915_gem_context_create create = { }; > - int ret = drmIoctl(bufmgr->fd, DRM_IOCTL_I915_GEM_CONTEXT_CREATE, & > create); > - if (ret != 0) { > - DBG("DRM_IOCTL_I915_GEM_CONTEXT_CREATE failed: %s\n", strerror > (errno)); > - return 0; > + struct local_i915_gem_context_create_v2 { > + uint32_t ctx_id; /* out */ > + uint32_t flags; > +#define I915_GEM_CONTEXT_SHARE_GTT 0x1 > + uint32_t share_ctx; > > > So, we've left share_ctx as 0. What does that mean? Does that mean that we > share with some context that was implicitly created by opening /dev/dri/card0? > Does it mean we share with the default context and therefore other processes? </div></div>The default context, 0, is per fd. </blockquote><div> </div><div>So a second open() of /dev/dri/card0 will get a different default context? </div></div> </div></div>