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
--
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
--- linux-2.6.15/drivers/ide/ide-dma.c 2006-01-19 20:53:01.000000000 +0100
+++ linux-2.6.15viahlt/drivers/ide/ide-dma.c 2006-01-20 12:00:32.000000000 +0100
@@ -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);
