linux-kernel - Re: [PATCH v2] fadvise: perform WILLNEED readahead asynchronously

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Date:	Thu, 10 Jan 2013 04:05:46 +0000
From:	Eric Wong <normalperson@...t.net>
To:	Simon Jeons <simon.jeons@...il.com>
Cc:	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Dave Chinner <david@...morbit.com>,
	Zheng Liu <gnehzuil.liu@...il.com>
Subject: Re: [PATCH v2] fadvise: perform WILLNEED readahead asynchronously

Simon Jeons <simon.jeons@...il.com> wrote:
> On Tue, 2012-12-25 at 02:22 +0000, Eric Wong wrote:
> 
> Please add changelog.

Changes since v1:

* separate unbound workqueue for high-priority tasks

* account for inflight readahead to avoid denial-of-service

* limit concurrency for non-high-priority tasks (1 per CPU, same as aio)

* take IO priority of requesting process into account when in workqueue.

* process queued readahead in 2M chunks to help ensure fairness between
  multiple requests with few CPUs/workqueues.  Idle tasks get smaller
  256K chunks.

* stops readahead for idle tasks on read congestion

Will try to benchmark with Postgres when I get the chance.

Any other (Free Software) applications that might benefit from
lower FADV_WILLNEED latency?
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