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  • 17:17
    yurivict commented #4318
  • 08:12
    abadams commented #4423
  • 08:10
    abadams commented #4423
  • 07:25
    alexreinking commented #4423
  • 04:42

    abadams on super_simplify

    Add test set expressions (compare)

  • 02:45
    abadams commented #4423
  • 02:14
    steven-johnson closed #4422
  • 02:14

    steven-johnson on master

    Small code simplifications at t… Improved formatting of the code Merge pull request #4420 from b… (compare)

  • 02:14
    steven-johnson closed #4420
  • 01:53
    alexreinking edited #4423
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    alexreinking edited #4423
  • 01:52
    alexreinking labeled #4423
  • 01:51

    steven-johnson on srj-autoscheduler-plugins

    Update test.py (compare)

  • 01:50

    steven-johnson on srj-autoscheduler-plugins

    foo (compare)

  • 01:33
    alexreinking edited #4423
  • 01:32
    alexreinking commented #4423
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    alexreinking edited #4423
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    alexreinking edited #4423
  • 00:53
    alexreinking opened #4423
  • 00:29
    BachiLi commented #4412
Zalman Stern
@zvookin
In fact copies are always that way right? When the copy returns it is done.
When we extend lowering of async to something other than semaphores and threads, we will likely need to expose asynchronous copies, and perhaps an entire event model in general.
Andrew Adams
@abadams
Yeah, but even if I make them async and ignore the problems that introduces, we're on a single stream
Zalman Stern
@zvookin
Well that's sort of true for Hexagon DMA if there's one engine.
I.e. yes for a device, but since the device is modeling a piece of hardware that has that restriction anyway, probably....
Andrew Adams
@abadams
I was initially trying to overlap device compute with device<->host copies. In the cuda backend this needs a lot more work for anything like that to happen.
Zalman Stern
@zvookin
In order to have DMA going both directions one needs two devices and those will not be a single stream.
Andrew Adams
@abadams
That's all I meant
Zalman Stern
@zvookin
So I think we need to keep the current model, but we should consider introducing a new one that allows much more asynchrony.
Whether that is just async versions of the copy routines or a full event model I'm not sure
I'm not sure it makes much sense to consider until we are looking at a different way of lowering async
I.e. in the current model, synchronous copy is probably required anyway. The thread doing it would just wait immediately if it wasn't synchronous.
"Event model" likely amounts to exposing the semaphore abstraction and arranging for it to be signaled by the device support code somehow
Andrew Adams
@abadams
Overlapping CPU computation with device stuff works fine. All use of the device_api occurs on a single thread. All the CPU compute occurs on another thread.
That's what I'm targeting for now
Zalman Stern
@zvookin
"CPU" is not necessarily correct there. It can be a different device too.
That is the common case for Hexagon right?
Andrew Adams
@abadams
For the hexagon DMA work so far, "CPU" is hexagon, and "device" is the dma engine
Zalman Stern
@zvookin
Ok, but the Hexagon may be invoked via offload.
Andrew Adams
@abadams
But yeah, I think it would work to have cross-device stuff going on in parallel
All use of each device interface would be on a single distinct thread
Zalman Stern
@zvookin
yes
Andrew Adams
@abadams
and there's no cross-device-interface serialization I think
so it would just work
Zalman Stern
@zvookin
That is what I was highlighting.
The only issue I see with this design is that the overhead of the thread may be too high to use for very lightweight hardware synchronization mechanisms. Other than that, I don't see a lot of reason to do the customized lowering.
I need to make a couple more changes to the hexagon DMA
Will try to do so today.
The test only calls buffer_copy, which is mostly as it should be.
Dillon Sharlet
@dsharletg
So BTW regarding hexagon offloading, I've been thinking we simply punt on that for now
and only target standalone
anything that we get working on standalone can be made to work with offloading without solving any "hard" problems like async + storage folding, it just might involve a lot of plumbing and infrastructure
Steven Johnson
@steven-johnson
re: the windows buildbots, proposed fix is out there.
Zalman Stern
@zvookin
I'll have to consider the implications, but I think the current stuff just works if the DMA things are scheduled inside an offloaded thing.
Dillon Sharlet
@dsharletg
I think there might be some hiccups with the device interface
that will need to get plumbed over via offloading
and I don't think that will happen transparently right now
it might be easy to make it work though
Zalman Stern
@zvookin
yeah, that's small boogs territory.
I guess I'm expecting it will have to work with offload very early on to have a useful test.
Andrew Adams
@abadams
@dsharletg the host->device case also works, but there's no benefit for cuda because the version without async already manages to overlap the cpu compute and copies in a subtle way.
Confused me for a while.
CPU compute -> synchronous copy -> async kernel launch -> next batch of CPU compute (overlapped with GPU kernel launch) -> synchronous copy (stalls until kernel launch is done) ->
Wait, so I guess the CPU compute is hidden under the GPU compute
not the copy
Dillon Sharlet
@dsharletg
That's great news!
Steven Johnson
@steven-johnson
I’m restarting the buildbot master now
Steven Johnson
@steven-johnson
On the recent issue of exported symbols varying between opt levels: it looks like CMake added a feature in 3.4 that attempts to auto-build a .def file for you on Windows, with the net effect of (mostly) acting like the gcc-ish default of “export all symbols”: https://blog.kitware.com/create-dlls-on-windows-without-declspec-using-new-cmake-export-all-feature/
I haven’t tried it (and we are talking about CMake here so who knows)...
Steven Johnson
@steven-johnson
We explicitly forbid using ‘.’ in a Func name since we use that as a separator internally, but we don’t seem to have a similar constraint on Var name. Deliberate or accidental?