From: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
To: Jeff Garzik <jeff@garzik.org>
Cc: linux-ide@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH] libata: add comment documenting PIO latency issues on UP
Date: Thu, 26 Nov 2009 17:11:16 +0100 [thread overview]
Message-ID: <200911261711.16954.bzolnier@gmail.com> (raw)
Based on:
http://lkml.indiana.edu/hypermail/linux/kernel/0908.2/01420.html
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
---
drivers/ata/libata-core.c | 7 +++++++
1 file changed, 7 insertions(+)
Index: b/drivers/ata/libata-core.c
===================================================================
--- a/drivers/ata/libata-core.c
+++ b/drivers/ata/libata-core.c
@@ -6624,6 +6624,13 @@ 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;
next reply other threads:[~2009-11-26 16:11 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-11-26 16:11 Bartlomiej Zolnierkiewicz [this message]
2009-12-03 7:36 ` [PATCH] libata: add comment documenting PIO latency issues on UP Jeff Garzik
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