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>

1 files changed, 40 insertions, 15 deletions

diff --git a/drivers/misc/sgi-gru/grumain.c b/drivers/misc/sgi-gru/grumain.c
index 0c7bd384f0cf..3398e54a762b 100644
--- a/drivers/misc/sgi-gru/grumain.c
+++ b/drivers/misc/sgi-gru/grumain.c
@@ -96,7 +96,7 @@ static int gru_reset_asid_limit(struct gru_state *gru, int asid)
 	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 @@ void gru_unload_context(struct gru_thread_state *gts, int savestate)
 	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 @@ void gru_unload_context(struct gru_thread_state *gts, int savestate)
 	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 @@ void gru_unload_context(struct gru_thread_state *gts, int savestate)
 	unlock_cch_handle(cch);
 
 	gru_free_gru_context(gts);
-	STAT(unload_context);
 }
 
 /*
@@ -554,11 +555,16 @@ void gru_load_context(struct gru_thread_state *gts)
 	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 @@ void gru_load_context(struct gru_thread_state *gts)
 	if (cch_start(cch))
 		BUG();
 	unlock_cch_handle(cch);
-
-	STAT(load_context);
 }
 
 /*
@@ -652,6 +656,27 @@ static int gru_retarget_intr(struct gru_thread_state *gts)
 #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 @@ void gru_steal_context(struct gru_thread_state *gts, int blade_id)
 			 * 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 @@ void gru_steal_context(struct gru_thread_state *gts, int blade_id)
 	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 @@ again:
 	}
 
 	if (!gts->ts_gru) {
+		STAT(load_user_context);
 		if (!gru_assign_gru_context(gts, blade_id)) {
 			preempt_enable();
 			mutex_unlock(&gts->ts_ctxlock);