commit 836ce679c0b5b5040164171afc33753396864b30
author Jack Steiner <steiner@sgi.com> Wed Jun 17 16:28:22 2009 -0700
committer Linus Torvalds <torvalds@linux-foundation.org> Thu Jun 18 13:04:00 2009 -0700
tree 786be786c29fa6821d8ee95668393cd43193a278
parent 6e9100741ca430eeef8022794f8b62a23a5916af

gru: change resource assignment for kernel threads

Change the way GRU resources are assigned for kernel threads.  GRU
contexts for kernel threads are now allocated on demand and can be stolen
by user processes when idle.  This allows MPI jobs to use ALL of the GRU
resources when the kernel is not using them.

Signed-off-by: Jack Steiner <steiner@sgi.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/misc/sgi-gru/grumain.c

diff --git a/drivers/misc/sgi-gru/grumain.c b/drivers/misc/sgi-gru/grumain.c
index 0c7bd38..3398e54 100644
--- a/drivers/misc/sgi-gru/grumain.c
+++ b/drivers/misc/sgi-gru/grumain.c
@@ -96,7 +96,7 @@
 	gid = gru->gs_gid;
 again:
 	for (i = 0; i < GRU_NUM_CCH; i++) {
-		if (!gru->gs_gts[i])
+		if (!gru->gs_gts[i] || is_kernel_context(gru->gs_gts[i]))
 			continue;
 		inuse_asid = gru->gs_gts[i]->ts_gms->ms_asids[gid].mt_asid;
 		gru_dbg(grudev, "gid %d, gts %p, gms %p, inuse 0x%x, cxt %d\n",
@@ -506,7 +506,8 @@
 	struct gru_context_configuration_handle *cch;
 	int ctxnum = gts->ts_ctxnum;
 
-	zap_vma_ptes(gts->ts_vma, UGRUADDR(gts), GRU_GSEG_PAGESIZE);
+	if (!is_kernel_context(gts))
+		zap_vma_ptes(gts->ts_vma, UGRUADDR(gts), GRU_GSEG_PAGESIZE);
 	cch = get_cch(gru->gs_gru_base_vaddr, ctxnum);
 
 	gru_dbg(grudev, "gts %p\n", gts);
@@ -514,7 +515,8 @@
 	if (cch_interrupt_sync(cch))
 		BUG();
 
-	gru_unload_mm_tracker(gru, gts);
+	if (!is_kernel_context(gts))
+		gru_unload_mm_tracker(gru, gts);
 	if (savestate)
 		gru_unload_context_data(gts->ts_gdata, gru->gs_gru_base_vaddr,
 					ctxnum, gts->ts_cbr_map,
@@ -526,7 +528,6 @@
 	unlock_cch_handle(cch);
 
 	gru_free_gru_context(gts);
-	STAT(unload_context);
 }
 
 /*
@@ -554,11 +555,16 @@
 	cch->tfm_done_bit_enable = 0;
 	cch->dsr_allocation_map = gts->ts_dsr_map;
 	cch->cbr_allocation_map = gts->ts_cbr_map;
-	asid = gru_load_mm_tracker(gru, gts);
-	cch->unmap_enable = 0;
-	for (i = 0; i < 8; i++) {
-		cch->asid[i] = asid + i;
-		cch->sizeavail[i] = gts->ts_sizeavail;
+
+	if (is_kernel_context(gts)) {
+		cch->unmap_enable = 1;
+	} else {
+		cch->unmap_enable = 0;
+		asid = gru_load_mm_tracker(gru, gts);
+		for (i = 0; i < 8; i++) {
+			cch->asid[i] = asid + i;
+			cch->sizeavail[i] = gts->ts_sizeavail;
+		}
 	}
 
 	err = cch_allocate(cch);
@@ -575,8 +581,6 @@
 	if (cch_start(cch))
 		BUG();
 	unlock_cch_handle(cch);
-
-	STAT(load_context);
 }
 
 /*
@@ -652,6 +656,27 @@
 #define next_gru(b, g)	(((g) < &(b)->bs_grus[GRU_CHIPLETS_PER_BLADE - 1]) ?  \
 				 ((g)+1) : &(b)->bs_grus[0])
 
+static int is_gts_stealable(struct gru_thread_state *gts,
+		struct gru_blade_state *bs)
+{
+	if (is_kernel_context(gts))
+		return down_write_trylock(&bs->bs_kgts_sema);
+	else
+		return mutex_trylock(&gts->ts_ctxlock);
+}
+
+static void gts_stolen(struct gru_thread_state *gts,
+		struct gru_blade_state *bs)
+{
+	if (is_kernel_context(gts)) {
+		up_write(&bs->bs_kgts_sema);
+		STAT(steal_kernel_context);
+	} else {
+		mutex_unlock(&gts->ts_ctxlock);
+		STAT(steal_user_context);
+	}
+}
+
 void gru_steal_context(struct gru_thread_state *gts, int blade_id)
 {
 	struct gru_blade_state *blade;
@@ -685,7 +710,7 @@
 			 * success are high. If trylock fails, try to steal a
 			 * different GSEG.
 			 */
-			if (ngts && mutex_trylock(&ngts->ts_ctxlock))
+			if (ngts && is_gts_stealable(ngts, blade))
 				break;
 			ngts = NULL;
 			flag = 1;
@@ -701,10 +726,9 @@
 	spin_unlock(&blade->bs_lock);
 
 	if (ngts) {
-		STAT(steal_context);
 		ngts->ts_steal_jiffies = jiffies;
-		gru_unload_context(ngts, 1);
-		mutex_unlock(&ngts->ts_ctxlock);
+		gru_unload_context(ngts, is_kernel_context(ngts) ? 0 : 1);
+		gts_stolen(ngts, blade);
 	} else {
 		STAT(steal_context_failed);
 	}
@@ -810,6 +834,7 @@
 	}
 
 	if (!gts->ts_gru) {
+		STAT(load_user_context);
 		if (!gru_assign_gru_context(gts, blade_id)) {
 			preempt_enable();
 			mutex_unlock(&gts->ts_ctxlock);