From 9cd13bdbae5d83399c375b34ee1eb35e16c10568 Mon Sep 17 00:00:00 2001 From: Bartlomiej Zolnierkiewicz Date: Thu, 26 Nov 2009 17:11:16 +0100 Subject: [PATCH] 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 Signed-off-by: Jeff Garzik --- drivers/ata/libata-core.c | 7 +++++++ 1 file changed, 7 insertions(+) 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;