Thread (70 messages) 70 messages, 11 authors, 2014-09-13

Re: [PATCH RESEND 0/1] AHCI: Optimize interrupt processing

From: Alexander Gordeev <hidden>
Date: 2013-08-09 08:22:20
Also in: linux-scsi, lkml
Subsystem: libata subsystem (serial and parallel ata drivers), the rest · Maintainers: Damien Le Moal, Niklas Cassel, Linus Torvalds

On Mon, Jul 29, 2013 at 07:46:53AM -0400, Tejun Heo wrote:
One thing which would probably be worthwhile tho is getting rid of the
bitmap based qc tag allocator in libata.  That one is just borderline
stupid to keep around on any setup which is supposed to be scalable.
Hi Tejun,

How about this approach?
diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c
index f218427..5c2a236 100644
--- a/drivers/ata/libata-core.c
+++ b/drivers/ata/libata-core.c
@@ -72,6 +72,8 @@
 #include "libata.h"
 #include "libata-transport.h"
 
+#include "../../block/blk-mq-tag.h"
+
 /* debounce timing parameters in msecs { interval, duration, timeout } */
 const unsigned long sata_deb_timing_normal[]		= {   5,  100, 2000 };
 const unsigned long sata_deb_timing_hotplug[]		= {  25,  500, 2000 };
@@ -1569,18 +1571,8 @@ unsigned ata_exec_internal_sg(struct ata_device *dev,
 
 	/* initialize internal qc */
 
-	/* XXX: Tag 0 is used for drivers with legacy EH as some
-	 * drivers choke if any other tag is given.  This breaks
-	 * ata_tag_internal() test for those drivers.  Don't use new
-	 * EH stuff without converting to it.
-	 */
-	if (ap->ops->error_handler)
-		tag = ATA_TAG_INTERNAL;
-	else
-		tag = 0;
-
-	if (test_and_set_bit(tag, &ap->qc_allocated))
-		BUG();
+	tag = blk_mq_get_tag(ap->qc_tags, GFP_ATOMIC, true);
+	BUG_ON(!ata_tag_internal(tag));
 	qc = __ata_qc_from_tag(ap, tag);
 
 	qc->tag = tag;
@@ -4733,21 +4725,17 @@ void swap_buf_le16(u16 *buf, unsigned int buf_words)
 static struct ata_queued_cmd *ata_qc_new(struct ata_port *ap)
 {
 	struct ata_queued_cmd *qc = NULL;
-	unsigned int i;
+	unsigned int tag;
 
 	/* no command while frozen */
 	if (unlikely(ap->pflags & ATA_PFLAG_FROZEN))
 		return NULL;
 
-	/* the last tag is reserved for internal command. */
-	for (i = 0; i < ATA_MAX_QUEUE - 1; i++)
-		if (!test_and_set_bit(i, &ap->qc_allocated)) {
-			qc = __ata_qc_from_tag(ap, i);
-			break;
-		}
+	tag = blk_mq_get_tag(ap->qc_tags, GFP_ATOMIC, false);
+	qc = __ata_qc_from_tag(ap, tag);
 
 	if (qc)
-		qc->tag = i;
+		qc->tag = tag;
 
 	return qc;
 }
@@ -4799,7 +4787,7 @@ void ata_qc_free(struct ata_queued_cmd *qc)
 	tag = qc->tag;
 	if (likely(ata_tag_valid(tag))) {
 		qc->tag = ATA_TAG_POISON;
-		clear_bit(tag, &ap->qc_allocated);
+		blk_mq_put_tag(ap->qc_tags, tag);
 	}
 }
 
@@ -5639,6 +5627,12 @@ struct ata_port *ata_port_alloc(struct ata_host *host)
 	if (!ap)
 		return NULL;
 
+	ap->qc_tags = blk_mq_init_tags(ATA_MAX_QUEUE, 1, NUMA_NO_NODE);
+	if (!ap->qc_tags) {
+		kfree(ap);
+		return NULL;
+	}
+
 	ap->pflags |= ATA_PFLAG_INITIALIZING | ATA_PFLAG_FROZEN;
 	ap->lock = &host->lock;
 	ap->print_id = -1;
@@ -5677,6 +5671,14 @@ struct ata_port *ata_port_alloc(struct ata_host *host)
 	return ap;
 }
 
+static void ata_port_free(struct ata_port *ap)
+{
+	kfree(ap->pmp_link);
+	kfree(ap->slave_link);
+	blk_mq_free_tags(ap->qc_tags);
+	kfree(ap);
+}
+
 static void ata_host_release(struct device *gendev, void *res)
 {
 	struct ata_host *host = dev_get_drvdata(gendev);
@@ -5691,9 +5693,7 @@ static void ata_host_release(struct device *gendev, void *res)
 		if (ap->scsi_host)
 			scsi_host_put(ap->scsi_host);
 
-		kfree(ap->pmp_link);
-		kfree(ap->slave_link);
-		kfree(ap);
+		ata_port_free(ap);
 		host->ports[i] = NULL;
 	}
 
diff --git a/include/linux/libata.h b/include/linux/libata.h
index eae7a05..4ff9494 100644
--- a/include/linux/libata.h
+++ b/include/linux/libata.h
@@ -126,7 +126,7 @@ enum {
 	ATA_DEF_QUEUE		= 1,
 	/* tag ATA_MAX_QUEUE - 1 is reserved for internal commands */
 	ATA_MAX_QUEUE		= 32,
-	ATA_TAG_INTERNAL	= ATA_MAX_QUEUE - 1,
+	ATA_TAG_INTERNAL	= 0,
 	ATA_SHORT_PAUSE		= 16,
 
 	ATAPI_MAX_DRAIN		= 16 << 10,
@@ -766,7 +766,7 @@ struct ata_port {
 	unsigned int		cbl;	/* cable type; ATA_CBL_xxx */
 
 	struct ata_queued_cmd	qcmd[ATA_MAX_QUEUE];
-	unsigned long		qc_allocated;
+	struct blk_mq_tags	*qc_tags;
 	unsigned int		qc_active;
 	int			nr_active_links; /* #links with active qcs */
 
Thanks.

-- 
tejun
-- 
Regards,
Alexander Gordeev
agordeev@redhat.com
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