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Questions about the function, queue_empty in dm-cache-policy-mq.c

DISCUSSION nick 2 participants 2 messages Jan 5, 2015

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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?
2. What hardware is this on ?
3. How scalable is this function in terms of NR_QUEUE_LEVELS and how many does it need to handle? Nick

#1 lore raw
Quoted 3 lines · nick

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.

Quoted 1 line

2. What hardware is this on ?

Irrelevant.

Quoted 1 line

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