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Restructure swapout tests after vm map locking was removed.

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Consolidate the regions covered by the process lock.
Combine similar conditions tests into one, e.g. all process flags can
be test with one logical operation.
Add check for in-exec state, since p_vmspace is dererenced.
Remove labels and goto by explicitly tracking state.
Update comments.

Reviewed by:	alc, markj (previous version)
Tested by:	pho (previous version)
Sponsored by:	The FreeBSD Foundation
MFC after:	2 weeks
Differential revision:	https://reviews.freebsd.org/D13693
This commit is contained in:
kib 2018-01-04 18:14:58 +00:00
parent 940b8981c3
commit 565ce2a986
1 changed files with 46 additions and 99 deletions
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145
sys/vm/vm_swapout.c
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@ -734,126 +734,73 @@ swapout_procs(int action)
struct proc *p;
struct thread *td;
int slptime;
bool didswap;
bool didswap, doswap;
MPASS((action & (VM_SWAP_NORMAL | VM_SWAP_IDLE)) != 0);
didswap = false;
retry:
sx_slock(&allproc_lock);
FOREACH_PROC_IN_SYSTEM(p) {
/*
* Filter out not yet fully constructed processes. Do
* not swap out held processes. Avoid processes which
* are system, exiting, execing, traced, already swapped
* out or are in the process of being swapped in or out.
*/
PROC_LOCK(p);
/*
* Watch out for a process in
* creation. It may have no
* address space or lock yet.
*/
if (p->p_state == PRS_NEW) {
if (p->p_state != PRS_NORMAL || p->p_lock != 0 || (p->p_flag &
(P_SYSTEM | P_WEXIT | P_INEXEC | P_STOPPED_SINGLE |
P_TRACED | P_SWAPPINGOUT | P_SWAPPINGIN | P_INMEM)) !=
P_INMEM) {
PROC_UNLOCK(p);
continue;
}
/*
* An aio daemon switches its
* address space while running.
* Perform a quick check whether
* a process has P_SYSTEM.
* Filter out exiting processes.
* Further consideration of this process for swap out
* requires iterating over its threads. We release
* allproc_lock here so that process creation and
* destruction are not blocked while we iterate.
*
* To later reacquire allproc_lock and resume
* iteration over the allproc list, we will first have
* to release the lock on the process. We place a
* hold on the process so that it remains in the
* allproc list while it is unlocked.
*/
if ((p->p_flag & (P_SYSTEM | P_WEXIT)) != 0) {
PROC_UNLOCK(p);
continue;
}
_PHOLD_LITE(p);
PROC_UNLOCK(p);
sx_sunlock(&allproc_lock);
PROC_LOCK(p);
if (p->p_lock != 1 || (p->p_flag & (P_STOPPED_SINGLE |
P_TRACED | P_SYSTEM)) != 0)
goto nextproc;
/*
* Only aiod changes vmspace. However, it will be
* skipped because of the if statement above checking
* for P_SYSTEM.
* Do not swapout a realtime process.
* Guarantee swap_idle_threshold1 time in memory.
* If the system is under memory stress, or if we are
* swapping idle processes >= swap_idle_threshold2,
* then swap the process out.
*/
if ((p->p_flag & (P_INMEM | P_SWAPPINGOUT | P_SWAPPINGIN)) !=
P_INMEM)
goto nextproc;
switch (p->p_state) {
default:
/*
* Don't swap out processes in any sort
* of 'special' state.
*/
break;
case PRS_NORMAL:
/*
* do not swapout a realtime process
* Check all the thread groups..
*/
FOREACH_THREAD_IN_PROC(p, td) {
thread_lock(td);
if (PRI_IS_REALTIME(td->td_pri_class)) {
thread_unlock(td);
goto nextproc;
}
slptime = (ticks - td->td_slptick) / hz;
/*
* Guarantee swap_idle_threshold1
* time in memory.
*/
if (slptime < swap_idle_threshold1) {
thread_unlock(td);
goto nextproc;
}
/*
* Do not swapout a process if it is
* waiting on a critical event of some
* kind or there is a thread whose
* pageable memory may be accessed.
*
* This could be refined to support
* swapping out a thread.
*/
if (!thread_safetoswapout(td)) {
thread_unlock(td);
goto nextproc;
}
/*
* If the system is under memory stress,
* or if we are swapping
* idle processes >= swap_idle_threshold2,
* then swap the process out.
*/
if ((action & VM_SWAP_NORMAL) == 0 &&
((action & VM_SWAP_IDLE) == 0 ||
slptime < swap_idle_threshold2)) {
thread_unlock(td);
goto nextproc;
}
thread_unlock(td);
}
/*
* If the pageout daemon didn't free enough pages,
* or if this process is idle and the system is
* configured to swap proactively, swap it out.
*/
_PRELE(p);
if (swapout(p) == 0)
didswap = true;
PROC_UNLOCK(p);
goto retry;
doswap = true;
FOREACH_THREAD_IN_PROC(p, td) {
thread_lock(td);
slptime = (ticks - td->td_slptick) / hz;
if (PRI_IS_REALTIME(td->td_pri_class) ||
slptime < swap_idle_threshold1 ||
!thread_safetoswapout(td) ||
((action & VM_SWAP_NORMAL) == 0 &&
slptime < swap_idle_threshold2))
doswap = false;
thread_unlock(td);
if (!doswap)
break;
}
nextproc:
if (doswap && swapout(p) == 0)
didswap = true;
PROC_UNLOCK(p);
sx_slock(&allproc_lock);
PRELE(p);
}
sx_sunlock(&allproc_lock);
/*
* If we swapped something out, and another process needed memory,
* then wakeup the sched process.