The means of finding ranges of free pages was changed for
vm_reserv_break in r348484, and there was found to improve performance minutely and reduce code size. This change applies a similar change to vm_reserv_reclaim_config, expecting similar benefits. This change also allows quick rejection of page ranges that are unsuitable on account of alignment or boundary issues, where those issues are processed a page at a time in the current implementation. For contrived test cases, this can make finding a reservation satisfying a major alignment requirement around 30 times faster. Tested by: pho Approved by: markj (mentor) Differential Revision: https://reviews.freebsd.org/D20274
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Doug Moore
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ed29b75ca3
commit
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@ -1166,11 +1166,90 @@ vm_reserv_reclaim_inactive(int domain)
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return (FALSE);
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}
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/*
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* Determine whether this reservation has free pages that satisfy the given
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* request for contiguous physical memory. Start searching from the lower
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* bound, defined by low_index.
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*
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* The free page queue lock must be held.
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*/
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static bool
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vm_reserv_test_contig(vm_reserv_t rv, u_long npages, vm_paddr_t low,
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vm_paddr_t high, u_long alignment, vm_paddr_t boundary)
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{
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vm_paddr_t pa, size;
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u_long changes;
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int bitpos, bits_left, i, hi, lo, n;
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vm_reserv_assert_locked(rv);
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size = npages << PAGE_SHIFT;
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pa = VM_PAGE_TO_PHYS(&rv->pages[0]);
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lo = (pa < low) ?
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((low + PAGE_MASK - pa) >> PAGE_SHIFT) : 0;
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i = lo / NBPOPMAP;
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changes = rv->popmap[i] | ((1UL << (lo % NBPOPMAP)) - 1);
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hi = (pa + VM_LEVEL_0_SIZE > high) ?
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((high + PAGE_MASK - pa) >> PAGE_SHIFT) : VM_LEVEL_0_NPAGES;
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n = hi / NBPOPMAP;
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bits_left = hi % NBPOPMAP;
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hi = lo = -1;
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for (;;) {
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/*
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* "changes" is a bitmask that marks where a new sequence of
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* 0s or 1s begins in popmap[i], with last bit in popmap[i-1]
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* considered to be 1 if and only if lo == hi. The bits of
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* popmap[-1] and popmap[NPOPMAP] are considered all 1s.
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*/
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changes ^= (changes << 1) | (lo == hi);
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while (changes != 0) {
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/*
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* If the next change marked begins a run of 0s, set
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* lo to mark that position. Otherwise set hi and
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* look for a satisfactory first page from lo up to hi.
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*/
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bitpos = ffsl(changes) - 1;
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changes ^= 1UL << bitpos;
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if (lo == hi) {
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lo = NBPOPMAP * i + bitpos;
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continue;
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}
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hi = NBPOPMAP * i + bitpos;
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pa = VM_PAGE_TO_PHYS(&rv->pages[lo]);
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if ((pa & (alignment - 1)) != 0) {
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/* Skip to next aligned page. */
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lo += (((pa - 1) | (alignment - 1)) + 1) >>
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PAGE_SHIFT;
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if (lo >= VM_LEVEL_0_NPAGES)
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return (false);
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pa = VM_PAGE_TO_PHYS(&rv->pages[lo]);
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}
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if (((pa ^ (pa + size - 1)) & ~(boundary - 1)) != 0) {
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/* Skip to next boundary-matching page. */
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lo += (((pa - 1) | (boundary - 1)) + 1) >>
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PAGE_SHIFT;
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if (lo >= VM_LEVEL_0_NPAGES)
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return (false);
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pa = VM_PAGE_TO_PHYS(&rv->pages[lo]);
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}
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if (lo * PAGE_SIZE + size <= hi * PAGE_SIZE)
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return (true);
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lo = hi;
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}
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if (++i < n)
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changes = rv->popmap[i];
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else if (i == n)
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changes = bits_left == 0 ? -1UL :
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(rv->popmap[n] | (-1UL << bits_left));
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else
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return (false);
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}
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}
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/*
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* Searches the partially populated reservation queue for the least recently
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* changed reservation with free pages that satisfy the given request for
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* contiguous physical memory. If a satisfactory reservation is found, it is
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* broken. Returns TRUE if a reservation is broken and FALSE otherwise.
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* broken. Returns true if a reservation is broken and false otherwise.
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*
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* The free page queue lock must be held.
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*/
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@ -1180,21 +1259,19 @@ vm_reserv_reclaim_contig(int domain, u_long npages, vm_paddr_t low,
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{
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vm_paddr_t pa, size;
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vm_reserv_t rv, rvn;
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int hi, i, lo, low_index, next_free;
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if (npages > VM_LEVEL_0_NPAGES - 1)
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return (FALSE);
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return (false);
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size = npages << PAGE_SHIFT;
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vm_reserv_domain_lock(domain);
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again:
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for (rv = TAILQ_FIRST(&vm_rvq_partpop[domain]); rv != NULL; rv = rvn) {
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rvn = TAILQ_NEXT(rv, partpopq);
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pa = VM_PAGE_TO_PHYS(&rv->pages[VM_LEVEL_0_NPAGES - 1]);
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if (pa + PAGE_SIZE - size < low) {
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pa = VM_PAGE_TO_PHYS(&rv->pages[0]);
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if (pa + VM_LEVEL_0_SIZE - size < low) {
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/* This entire reservation is too low; go to next. */
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continue;
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}
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pa = VM_PAGE_TO_PHYS(&rv->pages[0]);
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if (pa + size > high) {
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/* This entire reservation is too high; go to next. */
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continue;
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@ -1210,73 +1287,19 @@ vm_reserv_reclaim_contig(int domain, u_long npages, vm_paddr_t low,
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}
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} else
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vm_reserv_domain_unlock(domain);
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if (pa < low) {
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/* Start the search for free pages at "low". */
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low_index = (low + PAGE_MASK - pa) >> PAGE_SHIFT;
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i = low_index / NBPOPMAP;
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hi = low_index % NBPOPMAP;
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} else
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i = hi = 0;
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do {
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/* Find the next free page. */
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lo = ffsl(~(((1UL << hi) - 1) | rv->popmap[i]));
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while (lo == 0 && ++i < NPOPMAP)
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lo = ffsl(~rv->popmap[i]);
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if (i == NPOPMAP)
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break;
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/* Convert from ffsl() to ordinary bit numbering. */
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lo--;
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next_free = NBPOPMAP * i + lo;
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pa = VM_PAGE_TO_PHYS(&rv->pages[next_free]);
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KASSERT(pa >= low,
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("vm_reserv_reclaim_contig: pa is too low"));
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if (pa + size > high) {
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/* The rest of this reservation is too high. */
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break;
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} else if ((pa & (alignment - 1)) != 0 ||
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((pa ^ (pa + size - 1)) & ~(boundary - 1)) != 0) {
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/*
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* The current page doesn't meet the alignment
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* and/or boundary requirements. Continue
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* searching this reservation until the rest
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* of its free pages are either excluded or
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* exhausted.
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*/
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hi = lo + 1;
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if (hi >= NBPOPMAP) {
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hi = 0;
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i++;
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}
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continue;
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}
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/* Find the next used page. */
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hi = ffsl(rv->popmap[i] & ~((1UL << lo) - 1));
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while (hi == 0 && ++i < NPOPMAP) {
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if ((NBPOPMAP * i - next_free) * PAGE_SIZE >=
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size) {
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vm_reserv_reclaim(rv);
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vm_reserv_unlock(rv);
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return (TRUE);
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}
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hi = ffsl(rv->popmap[i]);
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}
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/* Convert from ffsl() to ordinary bit numbering. */
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if (i != NPOPMAP)
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hi--;
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if ((NBPOPMAP * i + hi - next_free) * PAGE_SIZE >=
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size) {
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vm_reserv_reclaim(rv);
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vm_reserv_unlock(rv);
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return (TRUE);
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}
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} while (i < NPOPMAP);
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if (vm_reserv_test_contig(rv, npages, low, high,
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alignment, boundary)) {
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vm_reserv_reclaim(rv);
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vm_reserv_unlock(rv);
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return (true);
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}
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vm_reserv_unlock(rv);
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vm_reserv_domain_lock(domain);
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if (rvn != NULL && !rvn->inpartpopq)
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goto again;
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}
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vm_reserv_domain_unlock(domain);
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return (FALSE);
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return (false);
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}
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/*
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