Changes between Version 6 and Version 7 of GpuWorkFetch

Timestamp:

Dec 26, 2008, 10:32:43 AM (16 years ago)

Author:

davea

Comment:

--

GpuWorkFetch

@@ -1 +1 @@
 = Work fetch and GPUs =
 
-== Current policy ==
-
- * Weighted round-robin simulation
-  * get per-project and overall CPU shortfalls
-  * see what misses deadline
- * If overall shortfall, get work from project with highest LTD
- * Scheduler request includes just "work_req_seconds".
-
-Problems:
-
-There may be no CPU shortfall, but GPU is idle
-
-If GPU is idle, we should get work from a project that potentially has jobs for it.
-
-If the project has both CPU and GPU jobs, we may need to tell to send only GPU jobs.
-
-LTD isn't meaningful with GPUs
-
-== New policy ==
-
-{{{
-A CPU job is one that uses only CPU time
-A CUDA job is one that uses CUDA (and may use CPU as well)
+== Problems with the current work fetch policy ==
+
+The current work-fetch policy is essentially:
+ * Do a weighted round-robin simulation, computing overall CPU shortfall
+ * If there's a shortfall, request work from the project with highest LTD
+
+The scheduler request has a single number "work_req_seconds"
+indicating the total duration of jobs being requested.
+
+This policy has various problems.
+
+ * There's no way for the client to say "I have N idle CPUs, so send me enough jobs to use them all".
+
+And many problems related to GPUs:
+
+ * There may be no CPU shortfall, but GPUs are idle; no work will be fetched.
+
+ * If a GPU is idle, we should get work from a project that potentially has jobs for it.
+
+ * If a project has both CPU and GPU jobs, we may need to tell it to send only GPU (or only CPU) jobs.
+
+ * LTD is computed solely on the basis of CPU time used, so it doesn't provide a meaningly comparison between projects that use only GPUs, or between a GPU project and a CPU project.
+
+This document proposes a work-fetch system that solves these problems.
+
+For simplicity, the design assumes that there is only one GPU time (CUDA).
+It is straightforward to extend the design to handle additional GPU types.
+
+== Terminology ==
+
+A job sent to a client is associated with an app version,
+which uses some number (possibly fractional) of CPUs and CUDA devices.
+
+ * A '''CPU job''' is one that uses only CPU.
+ * A '''CUDA job''' is one that uses CUDA (and may use CPU as well).
+
+== Scheduler request ==
+
+New fields in scheduler request message:
+
+'''double cpu_req_seconds''': number of CPU seconds requested
+
+'''double cuda_req_seconds''': number of CUDA seconds requested
+
+'''double ninstances_cpu''': send enough jobs to occupy this many CPUs
+
+'''double ninstances_cuda''': send enough jobs to occupy this many CUDA devs
+
+For compatibility with old servers, the message still has '''work_req_seconds''';
+this is the max of (cpu,cuda)_req_seconds.
+
+== Client ==
+
+New abstraction: '''processing resource''' or PRSC.
+There are two processing resource types: CPU and CUDA.
+
+Each PRSC has its own 
+
 ----------------------
 RESOURCE_WORK_FETCH