Aren
/
NetBSD
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

Must ... micro ... optimize! 

* Save an instruction in the transition from idle to have-process-to-
  switch-to, and eliminate two instructions that cause datadep-stalls
  on StrongARM And XScale (one in each idle block).
* Rearrange some other instructions to avoid datadep-stalls on StrongARM
  and XScale.
* Since cpu_do_powersave == 0 is by far the common case, avoid a
  pipeline flush by reordering the two idle blocks.
This commit is contained in:
thorpej 2002-08-17 01:08:21 +00:00
parent 1334ab7d1e
commit 50fe583069
1 changed files with 23 additions and 17 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

40
sys/arch/arm/arm32/cpuswitch.S
View File

@ -1,4 +1,4 @@
/* $NetBSD: cpuswitch.S,v 1.15 2002/08/16 15:25:54 thorpej Exp $ */
/* $NetBSD: cpuswitch.S,v 1.16 2002/08/17 01:08:21 thorpej Exp $ */
/*
* Copyright (c) 1994-1998 Mark Brinicombe.
@ -233,42 +233,45 @@ Lblock_userspace_access:
/*
* Idle loop, exercised while waiting for a process to wake up.
*
* NOTE: When we jump back to .Lswitch_search, we must have a
* pointer to whichqs in r7, which is what it is when we arrive
* here.
*/
/* LINTSTUB: Ignore */
ASENTRY_NP(idle)
#if defined(LOCKDEBUG)
bl _C_LABEL(sched_unlock_idle)
#endif
ldr r3, .Lcpu_do_powersave
/* Enable interrupts */
IRQenable
/* If we don't want to sleep, use a simpler loop. */
ldr r3, .Lcpu_do_powersave
ldr r7, Lwhichqs /* r7 = &whichqs */
ldr r3, [r3]
ldr r3, [r3] /* r3 = cpu_do_powersave */
teq r3, #0
beq .Lidle_nosleep
bne 2f
/* Powersave idle. */
/* Non-powersave idle. */
1: /* should maybe do uvm pageidlezero stuff here */
ldr r3, [r7] /* r3 = whichqs */
teq r3, #0x00000000
bne .Lswitch_search
b 1b
2: /* Powersave idle. */
ldr r4, Lcpufuncs
.Lidle_sleep:
ldr r3, [r7]
3: ldr r3, [r7] /* r3 = whichqs */
teq r3, #0x00000000
bne .Lswitch_search
/* if saving power, don't want to pageidlezero */
mov r0, #0
add lr, pc, #.Lidle_sleep - . - 8
add lr, pc, #3b - . - 8
ldr pc, [r4, #(CF_SLEEP)]
/* loops back around */
/* Non-powersave idle. */
.Lidle_nosleep:
/* should maybe do uvm pageidlezero stuff here */
ldr r3, [r7]
teq r3, #0x00000000
bne .Lswitch_search
b .Lidle_nosleep
/*
* Find a new process to run, save the current context and
@ -326,7 +329,10 @@ ENTRY(cpu_switch)
/* First phase : find a new process */
ldr r7, Lwhichqs
/* rem: r5 = old proc */
/* rem: r7 = &whichqs */
.Lswitch_search:
IRQdisable
@ -335,7 +341,6 @@ ENTRY(cpu_switch)
#endif
/* Do we have any active queues */
ldr r7, Lwhichqs
ldr r3, [r7]
/* If not we must idle until we do. */
@ -695,6 +700,7 @@ ENTRY(switch_exit)
mov r0, #0x00000000
str r0, [r1]
ldr r7, Lwhichqs /* r7 = &whichqs */
mov r5, #0x00000000 /* r5 = old proc = NULL */
b .Lswitch_search