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authorBartlomiej Zolnierkiewicz <bzolnier@gmail.com>2009-11-26 17:11:16 +0100
committerJeff Garzik <jgarzik@redhat.com>2009-12-03 14:36:16 -0500
commit9cd13bdbae5d83399c375b34ee1eb35e16c10568 (patch)
treefc8267f13a5e9af025bead6e215952503bb790fa /drivers/ata
parent5600c70e576199a7552e1c0fff43f3fe16f5566e (diff)
libata: add comment documenting PIO latency issues on UP
Based on: http://lkml.indiana.edu/hypermail/linux/kernel/0908.2/01420.html Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com> Signed-off-by: Jeff Garzik <jgarzik@redhat.com>
Diffstat (limited to 'drivers/ata')
-rw-r--r--drivers/ata/libata-core.c7
1 files changed, 7 insertions, 0 deletions
diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c
index dc72690ed5db..22ff51bdbc8a 100644
--- a/drivers/ata/libata-core.c
+++ b/drivers/ata/libata-core.c
@@ -6616,6 +6616,13 @@ static int __init ata_init(void)
{
ata_parse_force_param();
+ /*
+ * FIXME: In UP case, there is only one workqueue thread and if you
+ * have more than one PIO device, latency is bloody awful, with
+ * occasional multi-second "hiccups" as one PIO device waits for
+ * another. It's an ugly wart that users DO occasionally complain
+ * about; luckily most users have at most one PIO polled device.
+ */
ata_wq = create_workqueue("ata");
if (!ata_wq)
goto free_force_tbl;