* O_DIRECT for block device
@ 2005-09-22 8:21 Karthik Sarangan
2005-09-22 8:34 ` Avi Kivity
2005-09-22 8:40 ` Joel Becker
0 siblings, 2 replies; 4+ messages in thread
From: Karthik Sarangan @ 2005-09-22 8:21 UTC (permalink / raw)
To: linux-kernel
I have a scsi hdd configured at /dev/sdb.
open("/dev/sdb", O_DIRECT) succeeds.
A 'read' or 'write' returns -1 and errno is EINVAL.
How to read and write data to it? They do not seem to work. I have a
262144 byte buffer for data transfer.
My kernel is 2.6.9-11 and I use RedHat Enterprise Linux.
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: O_DIRECT for block device
2005-09-22 8:21 O_DIRECT for block device Karthik Sarangan
@ 2005-09-22 8:34 ` Avi Kivity
2005-09-22 8:40 ` Joel Becker
1 sibling, 0 replies; 4+ messages in thread
From: Avi Kivity @ 2005-09-22 8:34 UTC (permalink / raw)
To: Karthik Sarangan; +Cc: linux-kernel
Karthik Sarangan wrote:
> I have a scsi hdd configured at /dev/sdb.
>
> open("/dev/sdb", O_DIRECT) succeeds.
> A 'read' or 'write' returns -1 and errno is EINVAL.
>
> How to read and write data to it? They do not seem to work. I have a
> 262144 byte buffer for data transfer.
make sure your buffer is aligned on a 512 byte boundary.
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: O_DIRECT for block device
2005-09-22 8:21 O_DIRECT for block device Karthik Sarangan
2005-09-22 8:34 ` Avi Kivity
@ 2005-09-22 8:40 ` Joel Becker
[not found] ` <43329590.3050006@cdac.in>
1 sibling, 1 reply; 4+ messages in thread
From: Joel Becker @ 2005-09-22 8:40 UTC (permalink / raw)
To: Karthik Sarangan; +Cc: linux-kernel
On Thu, Sep 22, 2005 at 01:51:16PM +0530, Karthik Sarangan wrote:
> open("/dev/sdb", O_DIRECT) succeeds.
> A 'read' or 'write' returns -1 and errno is EINVAL.
You must align your buffer to at least sector size. See
posix_memalign(3).
--
Life's Little Instruction Book #30
"Never buy a house without a fireplace."
Joel Becker
Principal Software Developer
Oracle
E-mail: joel.becker@oracle.com
Phone: (650) 506-8127
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: O_DIRECT for block device
[not found] ` <20050922152028.GJ27375@ca-server1.us.oracle.com>
@ 2005-09-23 5:36 ` Karthik Sarangan
0 siblings, 0 replies; 4+ messages in thread
From: Karthik Sarangan @ 2005-09-23 5:36 UTC (permalink / raw)
To: Joel Becker; +Cc: linux-kernel
Joel Becker wrote:
> On Thu, Sep 22, 2005 at 04:59:20PM +0530, Karthik Sarangan wrote:
>
>>I tried your tip and the read works beautifully but the write returns -1
>>and errno = EBADF!
>
>
> Did you open with O_RDWR?
>
> Joel
>
Alright I didn't, though using O_DIRECT | O_RDWR the second time solved
it :-) I finally got 69MBps read and 49 MBps writes on my SCSI disk.
Thanks for helping me out.
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2005-09-23 5:42 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2005-09-22 8:21 O_DIRECT for block device Karthik Sarangan
2005-09-22 8:34 ` Avi Kivity
2005-09-22 8:40 ` Joel Becker
[not found] ` <43329590.3050006@cdac.in>
[not found] ` <20050922152028.GJ27375@ca-server1.us.oracle.com>
2005-09-23 5:36 ` Karthik Sarangan
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).