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* Re: [dm-devel] Questions about the function, queue_empty in dm-cache-policy-mq.c
       [not found] <54AA03E0.9020900@gmail.com>
@ 2015-01-05  9:17 ` Joe Thornber
  0 siblings, 0 replies; only message in thread
From: Joe Thornber @ 2015-01-05  9:17 UTC (permalink / raw)
  To: device-mapper development; +Cc: agk, linux-raid, linux-kernel, snitzer

On Sun, Jan 04, 2015 at 10:24:16PM -0500, nick wrote:
> Greetings All,
> I have a few questions about the function I stated in the message for this email.
> 1. What is the issues with the CPU usage for this function?

At the moment it can perform up to NR_QUEUE_LEVELS (16) list_empty()
calls.  Which I consider too much work for a function that is called
frequently.

> 2. What hardware is this on ?

Irrelevant.

> 3. How scalable is this function in terms of NR_QUEUE_LEVELS and how many does it need to handle?

Linear.  NR_QUEUE_LEVELS is a compile time constant currently set to
16, and unlikely to change.

- Joe

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2015-01-05  9:17 ` [dm-devel] Questions about the function, queue_empty in dm-cache-policy-mq.c Joe Thornber

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