On 4/23/19 4:28 PM, Aaron Plattner wrote:
On 4/17/19 8:51 AM, Kyle Brenneman wrote:
For GPU offloading in libglvnd, where individual clients can run with
an alternate GPU and client-side vendor library, we'd need some way
for that alternate vendor library to communicate with its server-side
counterpart. Normally, the server's GLXVND layer would dispatch any
GLX requests to whichever driver is running an X screen. This is a
GLX extension that allows a client to tell the server to send GLX
requests to a different driver instead.
The basic idea is that the server keeps a separate (screen ->
GLXServerVendor) mapping for each client. The current global mapping
is used as the default for each new client, but the client can send a
request to change its own mapping. That way, if the client uses a
different vendor library, then the client-side vendor can arrange for
any GLX requests to go to the matching server-side driver.
The extension uses Atoms as an ID to identify each GLXServerVendor,
using a string provided by the driver. That way, the client-side
driver can know which Atom it needs to use without having to define
an extra query. The client can send a request with a screen number
and a vendor ID to tell the server to dispatch any GLX requests for
that screen to the specified vendor. A client can also send None as a
vendor ID to revert to whatever GLXServerVendor would handle that
screen by default.
I also added a GLXVendorPrivate/GLXVendorPrivateWithReply-style
request, which sends a request to a specific vendor based on a vendor
ID, without having to worry about which vendor is assigned to a
screen at the moment. Strictly speaking, a vendor library could get
the same result by adding a regular GLXVendorPrivate request, and
providing a dispatch function that always routes the request to
itself, but that seems like it's more of an implementation detail of
GLXVND.
Also, this extension doesn't define any errors or queries to check
whether a GLXServerVendor can support a given screen. These requests
would be sent by a client-side vendor library (not by libglvnd or an
application), so each driver would be responsible for figuring out on
its own which screens it can support.
Anyway, I've got a draft of the extension spec here, and I've written
up a series of patches for the X server to implement it here:
https://gitlab.freedesktop.org/kbrenneman/xserver/tree/GLX_EXT_server_vendor_select
Hi Kyle,
Have you gotten any feedback on the commits there? It might help to
create an xorg/xserver merge request for them. You can use the "WIP:"
prefix on the MR title if you just want to request feedback without
actually getting it merged.
Not a bad idea. I've posted a merge request with the patches here, and
attached the extension spec:
https://gitlab.freedesktop.org/xorg/xserver/merge_requests/179
-Kyle
Comments and questions welcome.
-Kyle Brenneman
Name
EXT_server_vendor_select
Name Strings
GLX_EXT_server_vendor_select
Contact
Kyle Brenneman, NVIDIA, kbrenneman at nvidia.com
Contributors
Kyle Brenneman
Status
XXX - Not complete yet!!!
Version
Last Modified Date: April 11, 2019
Revision: 1
Number
OpenGL Extension #???
Dependencies
GLX version 1.2 is required.
This specification is written against the wording of the GLX 1.3
Protocol Encoding Specification.
Overview
In multi-GPU systems, a client may decide at runtime which device
and driver to use for GLX, for example to choose between a
high-performance and low-power device.
This extension defines a set of requests that allow a client to
specify which server-side driver should handle GLX requests from
the
sending client for a particular screen.
IP Status
No known IP claims.
New Procedures and Functions
None
New Tokens
None
Additions to the GLX Specification
None. These requests are intended to be used by a client-side GLX
implementation, not by an application. Therefore, this extension
does not define any new functions or changes to the GLX
specification.
GLX Protocol
Get a List of Server-Side Drivers
Name: glXQueryServerVendorIDsEXT
Description:
This request fetches a list of available server-side
drivers, and the current vendor ID selected for each
screen.
Each driver is identified by an Atom, with a string chosen
by the driver.
The reply contains a list of the currently selected vendors
first, with one Atom for each screen. This will be the
vendor selected with the glXSelectScreenServerVendorIDEXT
request, or the default vendor if the client has not sent a
glXSelectScreenServerVendorIDEXT request for a screen.
If a screen is using the default vendor, and the vendor
does
not have a vendor ID, then
