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work around swap-space/extent performance problem which causes

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long pauses when processes with lots of swapped-out pages exit.
This commit is contained in:
chs 2001-09-19 03:41:46 +00:00
parent 1a9410a9f1
commit 20a658f0ab
1 changed files with 19 additions and 5 deletions
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24
sys/uvm/uvm_amap.c
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@ -1,4 +1,4 @@
/* $NetBSD: uvm_amap.c,v 1.34 2001/09/15 20:36:44 chs Exp $ */
/* $NetBSD: uvm_amap.c,v 1.35 2001/09/19 03:41:46 chs Exp $ */
/*
*
@ -248,7 +248,7 @@ amap_alloc(sz, padsz, waitf)
/*
* amap_free: free an amap
*
* => the amap must be locked (mainly for simplelock accounting)
* => the amap must be unlocked
* => the amap should have a zero reference count and be empty
*/
void
@ -258,7 +258,7 @@ amap_free(amap)
UVMHIST_FUNC("amap_free"); UVMHIST_CALLED(maphist);
KASSERT(amap->am_ref == 0 && amap->am_nused == 0);
LOCK_ASSERT(simple_lock_held(&amap->am_l));
LOCK_ASSERT(!simple_lock_held(&amap->am_l));
free(amap->am_slots, M_UVMAMAP);
free(amap->am_bckptr, M_UVMAMAP);
free(amap->am_anon, M_UVMAMAP);
@ -266,7 +266,6 @@ amap_free(amap)
if (amap->am_ppref && amap->am_ppref != PPREF_NONE)
free(amap->am_ppref, M_UVMAMAP);
#endif
amap_unlock(amap); /* mainly for lock debugging */
pool_put(&uvm_amap_pool, amap);
UVMHIST_LOG(maphist,"<- done, freed amap = 0x%x", amap, 0, 0, 0);
}
@ -500,7 +499,7 @@ amap_wipeout(amap)
UVMHIST_FUNC("amap_wipeout"); UVMHIST_CALLED(maphist);
UVMHIST_LOG(maphist,"(amap=0x%x)", amap, 0,0,0);
LOCK_ASSERT(simple_lock_held(&amap->am_l));
amap_unlock(amap);
for (lcv = 0 ; lcv < amap->am_nused ; lcv++) {
int refs;
@ -523,6 +522,20 @@ amap_wipeout(amap)
uvm_anfree(anon);
}
/*
* XXX
* releasing the swap space held by an N anons is an O(N^2)
* operation because of the implementation of extents.
* if there are many anons, tearing down an exiting process'
* address space can take many seconds, which causes very
* annoying pauses. we yield here to give other processes
* a chance to run. this should be removed once the performance
* of swap space management is improved.
*/
if (curproc->p_cpu->ci_schedstate.spc_flags & SPCF_SHOULDYIELD)
preempt(NULL);
}
/*
@ -644,6 +657,7 @@ amap_copy(map, entry, waitf, canchunk, startva, endva)
if (srcamap->am_ref == 1) { /* take it over? */
entry->etype &= ~UVM_ET_NEEDSCOPY;
amap->am_ref--; /* drop final reference to map */
amap_unlock(amap);
amap_free(amap); /* dispose of new (unused) amap */
amap_unlock(srcamap);
return;