From: keith.busch@intel.com (Keith Busch)
Subject: coalescing in polling mode in 4.9
Date: Mon, 5 Feb 2018 08:02:53 -0700 [thread overview]
Message-ID: <20180205150253.GN24417@localhost.localdomain> (raw)
In-Reply-To: <20180202001028.fee27cf239e3e8a5ae6bd8a4@gmail.com>
On Fri, Feb 02, 2018@12:10:28AM -0800, Alex Nln wrote:
> Enabling interrupt coalescing in nvme device, kernel 4.9
> significantly reduces performance when using polling mode.
> When I enable coalescing, IOPS drops from 100K to 35K and
> latency jumps from 7 usec to 25 usec.
>
> Shouldn't we expect performance boost in polling mode when
> interrupt coalescing enabled?
>
>
> Device is Intel DC P3600
That's a pretty low latency for this device. Are you running reads to
unmapped blocks?
I've seen the phenomenom occur where higher coalescing settings worsens
performance. That usually means the the polling thread exceeded its time:
need_resched() returns true, so the tasks schedules out and relies on
interrupts, which have been throttled. Maybe a hybrid polling would be
better for this.
next prev parent reply other threads:[~2018-02-05 15:02 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-02-02 8:10 coalescing in polling mode in 4.9 Alex Nln
2018-02-05 0:15 ` Alex Nln
2018-02-05 14:40 ` Sagi Grimberg
2018-02-05 15:02 ` Keith Busch [this message]
2018-02-05 15:42 ` Nitesh
2018-02-06 5:39 ` Alex Nln
2018-02-09 22:37 ` Nitesh Shetty
2018-02-10 21:08 ` Alex Nln
2018-02-12 14:53 ` Keith Busch
2018-02-06 16:29 ` Keith Busch
2018-02-07 8:27 ` Nitesh
2018-02-06 3:55 ` Alex Nln
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