New submission from Venkatesh Srinivas <me@acm.jhu.edu>:
--- vm_zeroidle.c.orig 2010-05-26 15:09:26 -0700
+++ vm_zeroidle.c 2010-05-26 15:12:50 -0700
@@ -90,6 +90,9 @@
STATE_RELEASE_PAGE
};
+#define DEFAULT_SLEEP_TIME (hz / 10)
+#define LONG_SLEEP_TIME (hz * 10)
+
static int zero_state;
/*
@@ -112,6 +115,20 @@
return (1);
}
+/*
+ * vm_pagezero should sleep for a long time when idlezero is disabled or when
+ * there is an excess of zeroed pages.
+ */
+static int
+vm_page_zero_time(void)
+{
+ if (idlezero_enable == 0)
+ return (LONG_SLEEP_TIME);
+ if (vm_page_zero_count >= ZIDLE_HI(vmstats.v_free_count))
+ return (LONG_SLEEP_TIME);
+ return (DEFAULT_SLEEP_TIME);
+}
+
static void
vm_pagezero(void __unused *arg)
{
@@ -120,6 +137,7 @@
enum zeroidle_state state = STATE_IDLE;
char *pg = NULL;
int npages = 0;
+ int sleep_time;
int i = 0;
/*
@@ -132,6 +150,7 @@
rel_mplock();
lwkt_setpri_self(TDPRI_IDLE_WORK);
lwkt_setcpu_self(globaldata_find(ncpus - 1));
+ sleep_time = DEFAULT_SLEEP_TIME;
/*
* Loop forever
@@ -142,9 +161,10 @@
/*
* Wait for work.
*/
- tsleep(&zero_state, 0, "pgzero", hz / 10);
+ tsleep(&zero_state, 0, "pgzero", sleep_time);
if (vm_page_zero_check())
npages = idlezero_rate / 10;
+ sleep_time = vm_page_zero_time();
if (npages)
state = STATE_GET_PAGE; /* Fallthrough */
break;
@@ -198,7 +218,8 @@
}
break;
}
- lwkt_switch();
+ if (lwkt_check_resched(curthread))
+ lwkt_switch();
}
}
=================================
The patch above should cause vm_zeroidle to sleep for longer periods of time (hz
* 10) when it is disabled or when there are a lot of pages. Longer sleep times
would be better when there're no pages to zero.
It also conditionalizes the lwkt_switch(); I think this is worth doing, since
lwkt_check_resched() is cheaper than lwkt_switch(). This may or may not be worth
doing.
-- vs
----------
messages: 8623
nosy: vsrinivas
status: unread
title: patch: Add variable sleep time to vm_zeroidle
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DragonFly issue tracker <bugs@lists.dragonflybsd.org>
<http://bugs.dragonflybsd.org/issue1773>
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