IDE <-> CPU-HLT performance problem on VIA

PATCH New Helmut Toplitzer 1 participant 1 message Aug 7, 2006 libata

lore

Share & tools

lore

Helmut Toplitzer

author

2006-08-07 18:22 UTC #0 lore raw

PATCH 1/1 IDE <-> CPU-HLT performance problem on VIA

Hello!

I reported earlier (2.6.15) that there is a performance problem with USB subsystems and IDE controllers with current kernels on some VIA chipsets (at least one of VT82C586A/B/VT82C686/A/B/VT823x/A/C).

The performance-degradation - which still exists - is more than 1/3 and so you can get 150% IDE performance with a simple patch.
(See before.txt and after.txt for test-cases)

Is it possible that this or a simmilar patch gets applied to mainline? It might be a good idea to implement this with something like a "online detection" if the kernel notices this degradation but I've no idea how to do this. Maybe someone can help.

Helmut

Signature · 2 lines

My GNUpg fingerprint http://www.gnupg.org
4563 F4FB 0B7E 8698 53CD  00E9 E319 35BD 6A91 1656

# dd if=/dev/zero of=/tmp/test.txt bs=512
2214962+0 records in
2214961+0 records out
1134060032 bytes transferred in 32.199046 seconds (35220299 bytes/sec)

# hdparm -t /dev/hda

/dev/hda:
Timing buffered disk reads: 162 MB in 3.00 seconds = 53.92 MB/sec

$ sync
$ dd if=/dev/zero of=/tmp/test.txt bs=512
1469919+0 Datensätze ein
1469918+0 Datensätze aus
752598016 bytes transferred in 36,126547 seconds (20832271 bytes/sec)

$ rm /tmp/test.txt 
$ sync
$ burnK7 &
[1] 6535
$ dd if=/dev/zero of=/tmp/test.txt bs=512
1966168+0 Datensätze ein
1966167+0 Datensätze aus
1006677504 bytes transferred in 35,200795 seconds (28598147 bytes/sec)
# killall burnK7
# sync
# hdparm -t /dev/hda

/dev/hda:
Timing buffered disk reads: 76 MB in 3.01 seconds = 25.25 MB/sec
# burnK7 &
[1] 6547

# hdparm -t /dev/hda

/dev/hda:
Timing buffered disk reads: 166 MB in 3.01 seconds = 55.18 MB/sec

drivers/ide/ide-dma.c +53 -0

@@ -90,6 +90,57 @@
 #include <asm/io.h>
 #include <asm/irq.h>
 
+
+/* Some VIA boards show strange slowdown when HLT is eanbled  */
+/* So we disable the HLT during a IDE-DMA transfer.           */
+/* You need to pass disableviahlt at boottime to enable this  */
+/* workaround.                                                */
+#if defined(CONFIG_BLK_DEV_VIA82CXXX) && defined(HAVE_DISABLE_HLT)
+
+static DEFINE_SPINLOCK(ide_hlt_lock);
+static int hlt_disabled;
+static int disableviahlt;
+static void ide_disable_hlt(void)
+{
+	unsigned long flags;
+	
+	spin_lock_irqsave(&ide_hlt_lock, flags);
+	if(disableviahlt) {
+		hlt_disabled++ ;
+		disable_hlt();
+	}
+	spin_unlock_irqrestore(&ide_hlt_lock, flags);
+}
+
+static void ide_enable_hlt(void)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&ide_hlt_lock, flags);
+	if(hlt_disabled && disableviahlt){
+		hlt_disabled--;
+		enable_hlt();
+	}
+	spin_unlock_irqrestore(&ide_hlt_lock, flags);
+}
+
+static int __init disable_via_hlt(char *str)
+{
+    printk(KERN_WARNING "DISABLE VIA HLT  activated\n");
+    disableviahlt = 1;
+    return 1;
+}
+
+__setup("disableviahlt", disable_via_hlt);
+
+
+#else  /* CONFIG_BLK_DEV_VIA82CXXX && HAVE_DISABLE_HLT */
+inline static void ide_disable_hlt(void)
+{}
+inline static void ide_enable_hlt(void)
+{}
+#endif /* CONFIG_BLK_DEV_VIA82CXXX && HAVE_DISABLE_HLT */
+
 static const struct drive_list_entry drive_whitelist [] = {
 
 	{ "Micropolis 2112A"	,       "ALL"		},

@@ -303,6 +354,7 @@
 	if (count) {
 		if (!is_trm290)
 			*--table |= cpu_to_le32(0x80000000);
+		ide_disable_hlt();
 		return count;
 	}
 	printk(KERN_ERR "%s: empty DMA table?\n", drive->name);

@@ -334,6 +386,7 @@
 	int nents = HWIF(drive)->sg_nents;
 
 	pci_unmap_sg(dev, sg, nents, HWIF(drive)->sg_dma_direction);
+	ide_enable_hlt();
 }
 
 EXPORT_SYMBOL_GPL(ide_destroy_dmatable);