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From: Keith Busch <kbusch@kernel.org>
To: Mark Ruijter <MRuijter@onestopsystems.com>
Cc: "linux-nvme@lists.infradead.org" <linux-nvme@lists.infradead.org>,
	"hch@lst.de" <hch@lst.de>,
	Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>,
	"sagi@grimberg.me" <sagi@grimberg.me>
Subject: Re: [PATCH] nvmet: introduce use_vfs ns-attr
Date: Fri, 25 Oct 2019 13:05:40 +0900
Message-ID: <20191025040540.GA19941@redsun51.ssa.fujisawa.hgst.com> (raw)
In-Reply-To: <FA6B6A9F-649B-4B58-99D0-2D09076E2482@onestopsystems.com>

On Thu, Oct 24, 2019 at 11:30:18AM +0000, Mark Ruijter wrote:
> Note that I wrote this patch to prove that a performance problem exists when using raid1.
> Either the md raid1 driver or the io-cmd-bdev.c code has issues.
> When you add an additional layer like the VFS the performance should typically drop with 5~10%.
> However in this case the performance increases even though the nvme target uses direct-io and the random writes do not get merged by the VFS.

Are we really using direct io when nvme target is going through vfs,
though? That should happen if we've set IOCB_DIRECT in the ki_flags,
but I don't see that happening, and if that's right, then the difference
sounds like it's related to buffered IO.

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Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-23 20:17 Chaitanya Kulkarni
2019-10-24  2:00 ` Keith Busch
2019-10-24 11:30   ` Mark Ruijter
2019-10-25  4:05     ` Keith Busch [this message]
2019-10-25  4:26       ` Keith Busch
2019-10-25  8:44         ` Mark Ruijter
2019-10-26  1:06           ` Keith Busch
2019-10-27 15:03           ` hch
2019-10-27 16:06             ` Mark Ruijter
2019-10-28  0:55             ` Keith Busch
2019-10-28  7:26               ` Chaitanya Kulkarni
2019-10-28  7:32               ` Chaitanya Kulkarni
2019-10-28  7:35                 ` hch
2019-10-28  7:38                   ` Chaitanya Kulkarni
2019-10-28  7:43                     ` hch
2019-10-28  8:04                       ` Chaitanya Kulkarni
2019-10-28  8:01                 ` Keith Busch
2019-10-28  8:41                   ` Mark Ruijter
2019-10-25  3:29   ` Chaitanya Kulkarni

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