Commit 86df5984 authored Jan 28, 2017 by James Simmons Committed by Greg Kroah-Hartman Feb 03, 2017

staging: lustre: osc: avoid 64 divide in osc_cache_too_much



The use of 64 bit time introduces an expensive 64 bit
division operation. Since the time lapse being calculated
in osc_cache_too_much will never be more than seventy years
we can cast the time lapse to an long and perform a normal
32 bit divison operation instead.

Signed-off-by: James Simmons <uja.ornl@yahoo.com>
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-8835
Reviewed-on: https://review.whamcloud.com/23814


Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Dmitry Eremin <dmitry.eremin@intel.com>
Signed-off-by: James Simmons <jsimmons@infradead.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent 1cf96da2

drivers/staging/lustre/lustre/osc/osc_page.c

+8 −3

Original line number	Diff line number	Diff line
		@@ -370,12 +370,17 @@ static int osc_cache_too_much(struct client_obd *cli)
		return lru_shrink_min(cli);
		} else {
		time64_t duration = ktime_get_real_seconds();
		long timediff;

		/* knock out pages by duration of no IO activity */
		duration -= cli->cl_lru_last_used;
		duration >>= 6; /* approximately 1 minute */
		if (duration > 0 &&
		pages >= div64_s64((s64)budget, duration))
		/*
		* The difference shouldn't be more than 70 years
		* so we can safely case to a long. Round to
		* approximately 1 minute.
		*/
		timediff = (long)(duration >> 6);
		if (timediff > 0 && pages >= budget / timediff)
		return lru_shrink_min(cli);
		}
		return 0;