From: Karthik Sarangan <karthiks@cdac.in>
To: Benjamin LaHaise <bcrl@kvack.org>
Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Linux SCSI Mailing List <linux-scsi@vger.kernel.org>
Subject: Re: AIO!!
Date: Tue, 11 Oct 2005 10:34:01 +0530 [thread overview]
Message-ID: <434B47C1.60106@cdac.in> (raw)
In-Reply-To: <20051010160856.GI13986@kvack.org>
> Benjamin LaHaise wrote:
> O_DIRECT buffers must be aligned on block sized boundaries (minimum 512
> bytes). Check the actual return code from the aiocb and you'll find that
> it is likely -EINVAL, no -EINPROGRESS. See the man page for
> posix_memalign() to properly align the pointer.
>
EEP!! I forgot all about buffer alignment!! Thanks for pointing it out
:)
------------------
Two more questions.
1. Is aio_fsync of any use while 'aio_read'ing and 'aio_write'ing to
a 'raw' device or a '/dev/sdb' with O_DIRECT?
2. I have an Ultra320 SCSI disk whose datasheet says it has a max.
possible throughput of 78MBps
I did a 'aio_write' onto '/dev/sdb' with O_DIRECT.
Following are some throughput values.
Buffer for IO | Avg Speed
(in KBytes) |
----------------O-----------
Upto 512KB | 69MBps
1024KB | 125MBps
2048KB | 250MBps
4096KB | 500MBps
8192KB | 1GBps -- What the !! --
Buffer cache does not come into consideration.
Does this mean that the SCSI lower layer (aic79xx) can transfer data
only upto 512 KB?
next prev parent reply other threads:[~2005-10-11 5:10 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-10-10 13:39 AIO!! Karthik Sarangan
2005-10-10 16:08 ` AIO!! Benjamin LaHaise
2005-10-11 5:04 ` Karthik Sarangan [this message]
2005-10-11 9:25 ` AIO!! Denis Vlasenko
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