Linux-kernel mailing list archive 2000-26,: Re: a joint letter on low latency and Linux

# Re: a joint letter on low latency and Linux

Andre Hedrick (andre@linux-ide.org)
Fri, 30 Jun 2000 22:23:09 -0700 (PDT)

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/*
* Timeouts for various operations:
*/
#define WAIT_DRQ (5*HZ/100) /* 50msec - spec allows up to 20ms */
#ifdef CONFIG_APM
#define WAIT_READY (5*HZ) /* 5sec - some laptops are very slow */
#else
#define WAIT_READY (3*HZ/100) /* 30msec - should be instantaneous */
#endif /* CONFIG_APM */
#define WAIT_PIDENTIFY (10*HZ) /* 10sec - should be less than 3ms (?)
if all ATAPI CD is closed at boot */
#define WAIT_WORSTCASE (30*HZ) /* 30sec - worst case when spinning up */
#define WAIT_CMD (10*HZ) /* 10sec - maximum wait for an IRQ to happen */
#define WAIT_MIN_SLEEP (2*HZ/100) /* 20msec - minimum sleep time */

Look, I do not care what HZ is used, I have a fixed timeout base that I
have to work with in order for ATA/ATAPI to work period. Blowing these
values will be a damn excellent way to crap out the entire sub-system.

This is my concern. I do not care how we address it, I have to be able to
clock intervals in a predictable fashion.

Cheers,

Andre Hedrick
The Linux ATA/IDE guy

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