[Cbe-oss-dev] [PATCH] libspe2: add SPE_NOSCHED to spe_context_create()

[Gerhard Stenzel]

This patch adds a new flag for spe_context_create() that ensures that a
program can "keep" an SPE until it runs to completion. In other words,
the physical SPE resource that runs this context becomes "invisible" to
the SPE scheduler and can't be used to run other context, even if they
have higher priority. Because of this behaviour, this function is
considered a privileged operation. The process needs "CAP_SYS_NICE"
capability in Linux (see capabilities(7)) - which usually only root has.

Please note also, that this requires the following patches

 powerpc/spufs: allow spu_acquire_saved to correctly handle NOSCHED contexts
 powerpc/spufs: consolidate contexts of normal and NOSCHED context directories

sent by Jeremy Kerr to cbe-oss-dev August, the 1st, 2008 
to be applied to the kernel, otherwise SPE_NOSCHED will fail.

Signed-off-by: Gerhard Stenzel <stenzel at de.ibm.com>

===================================================================
Index: libspe2/spebase/create.c
===================================================================
--- libspe2/spebase/create.c	(revision 129)
+++ libspe2/spebase/create.c	(working copy)
@@ -231,6 +231,9 @@ spe_context_ptr_t _base_spe_context_crea
 	}
 
 	/* initialise spu_createflags */
+	if (flags & SPE_NOSCHED)
+		spu_createflags |=  SPU_CREATE_NOSCHED;
+
 	if (flags & SPE_ISOLATE) {
 		flags |= SPE_MAP_PS;
 		spu_createflags |= SPU_CREATE_ISOLATE | SPU_CREATE_NOSCHED;
Index: libspe2/libspe2-types.h
===================================================================
--- libspe2/libspe2-types.h	(revision 129)
+++ libspe2/libspe2-types.h	(working copy)
@@ -180,6 +180,7 @@ enum ps_area { SPE_MSSYNC_AREA, SPE_MFC_
 #define SPE_ISOLATE_EMULATE			0x00000100
 #define SPE_EVENTS_ENABLE			0x00001000
 #define SPE_AFFINITY_MEMORY			0x00002000
+#define SPE_NOSCHED				0x00004000
 
 
 /**

===================================================================

Best regards, 

Gerhard Stenzel, Linux on Cell Development, LTC
-------------------------------------------------------------------------------------
IBM Deutschland Research & Development GmbH
Vorsitzender des Aufsichtsrats: Martin Jetter | Geschaeftsfuehrung: Herbert Kircher
Sitz der Gesellschaft: Boeblingen | Registergericht: Amtsgericht Stuttgart, HRB 243294