From: Andrei Vagin <avagin@virtuozzo.com>
To: target-devel@vger.kernel.org
Subject: Re: [PATCH] [RFC] target/file: add support of direct and async I/O
Date: Thu, 15 Mar 2018 17:04:50 +0000 [thread overview]
Message-ID: <20180315170449.GA23171@outlook.office365.com> (raw)
In-Reply-To: <20180309004259.16052-1-avagin@openvz.org>
On Thu, Mar 15, 2018 at 09:26:57AM -0500, Bryant G. Ly wrote:
> On 3/8/18 6:42 PM, Andrei Vagin wrote:
>
> > Direct I/O allows to not affect the write-back cache, this is
> > expected when a non-buffered mode is used.
> >
> > Async I/O allows to handle a few commands concurrently, so a target shows a
> > better perfomance:
> >
> > Mode: O_DSYNC Async: 1
> > $ ./fio --bs=4K --direct=1 --rw=randwrite --ioengine=libaio --iodepthd --name=/dev/sda --runtime --numjobs=2
> > WRITE: bwE.9MiB/s (48.1MB/s), 21.9MiB/s-23.0MiB/s (22.0MB/s-25.2MB/s), io‘9MiB (963MB), run 002-20020msec
> >
> > Mode: O_DSYNC Async: 0
> > $ ./fio --bs=4K --direct=1 --rw=randwrite --ioengine=libaio --iodepthd --name=/dev/sdb --runtime --numjobs=2
> > WRITE: bw\x1607KiB/s (1645kB/s), 802KiB/s-805KiB/s (821kB/s-824kB/s), io1.8MiB (33.4MB), run 280-20295msec
> >
> > Known issue:
> >
> > DIF (PI) emulation doesn't work when a target uses async I/O, because
> > DIF metadata is saved in a separate file, and it is another non-trivial
> > task how to synchronize writing in two files, so that a following read
> > operation always returns a consisten metadata for a specified block.
> >
> > Cc: "Nicholas A. Bellinger" <nab@linux-iscsi.org>
> > Signed-off-by: Andrei Vagin <avagin@openvz.org>
> > ---
> > drivers/target/target_core_file.c | 124 ++++++++++++++++++++++++++++++++++++--
> > drivers/target/target_core_file.h | 1 +
> > 2 files changed, 120 insertions(+), 5 deletions(-)
> >
> >
> Tested-by: Bryant G. Ly <bryantly@linux.vnet.ibm.com>
>
> Patch looks good to me - Thanks for the performance enhancement!
>
> Btw I have been running I/O tests with HTX against this patch for 24 hrs and have no problems.
Bryant, thank you for the feedback.
>
> -Bryant
>
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next prev parent reply other threads:[~2018-03-15 17:04 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-03-09 0:42 [PATCH] [RFC] target/file: add support of direct and async I/O Andrei Vagin
2018-03-15 14:26 ` Bryant G. Ly
2018-03-15 17:04 ` Andrei Vagin [this message]
2018-03-16 7:50 ` Christoph Hellwig
2018-03-17 0:13 ` Andrei Vagin
2018-03-17 8:25 ` Christoph Hellwig
2018-03-20 7:54 ` Andrei Vagin
2018-03-20 8:47 ` Christoph Hellwig
2018-03-20 20:41 ` Andrei Vagin
2018-03-21 7:23 ` Christoph Hellwig
2018-03-21 18:16 ` Andrei Vagin
2018-03-21 18:47 ` Christoph Hellwig
2018-03-21 20:25 ` Andrei Vagin
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