Author: dougm Date: Thu Jun 6 16:28:34 2019 New Revision: 348749 URL: https://svnweb.freebsd.org/changeset/base/348749
Log: 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 Modified: head/sys/vm/vm_reserv.c Modified: head/sys/vm/vm_reserv.c ============================================================================== --- head/sys/vm/vm_reserv.c Thu Jun 6 16:27:05 2019 (r348748) +++ head/sys/vm/vm_reserv.c Thu Jun 6 16:28:34 2019 (r348749) @@ -1167,10 +1167,89 @@ vm_reserv_reclaim_inactive(int domain) } /* + * Determine whether this reservation has free pages that satisfy the given + * request for contiguous physical memory. Start searching from the lower + * bound, defined by low_index. + * + * The free page queue lock must be held. + */ +static bool +vm_reserv_test_contig(vm_reserv_t rv, u_long npages, vm_paddr_t low, + vm_paddr_t high, u_long alignment, vm_paddr_t boundary) +{ + vm_paddr_t pa, size; + u_long changes; + int bitpos, bits_left, i, hi, lo, n; + + vm_reserv_assert_locked(rv); + size = npages << PAGE_SHIFT; + pa = VM_PAGE_TO_PHYS(&rv->pages[0]); + lo = (pa < low) ? + ((low + PAGE_MASK - pa) >> PAGE_SHIFT) : 0; + i = lo / NBPOPMAP; + changes = rv->popmap[i] | ((1UL << (lo % NBPOPMAP)) - 1); + hi = (pa + VM_LEVEL_0_SIZE > high) ? + ((high + PAGE_MASK - pa) >> PAGE_SHIFT) : VM_LEVEL_0_NPAGES; + n = hi / NBPOPMAP; + bits_left = hi % NBPOPMAP; + hi = lo = -1; + for (;;) { + /* + * "changes" is a bitmask that marks where a new sequence of + * 0s or 1s begins in popmap[i], with last bit in popmap[i-1] + * considered to be 1 if and only if lo == hi. The bits of + * popmap[-1] and popmap[NPOPMAP] are considered all 1s. + */ + changes ^= (changes << 1) | (lo == hi); + while (changes != 0) { + /* + * If the next change marked begins a run of 0s, set + * lo to mark that position. Otherwise set hi and + * look for a satisfactory first page from lo up to hi. + */ + bitpos = ffsl(changes) - 1; + changes ^= 1UL << bitpos; + if (lo == hi) { + lo = NBPOPMAP * i + bitpos; + continue; + } + hi = NBPOPMAP * i + bitpos; + pa = VM_PAGE_TO_PHYS(&rv->pages[lo]); + if ((pa & (alignment - 1)) != 0) { + /* Skip to next aligned page. */ + lo += (((pa - 1) | (alignment - 1)) + 1) >> + PAGE_SHIFT; + if (lo >= VM_LEVEL_0_NPAGES) + return (false); + pa = VM_PAGE_TO_PHYS(&rv->pages[lo]); + } + if (((pa ^ (pa + size - 1)) & ~(boundary - 1)) != 0) { + /* Skip to next boundary-matching page. */ + lo += (((pa - 1) | (boundary - 1)) + 1) >> + PAGE_SHIFT; + if (lo >= VM_LEVEL_0_NPAGES) + return (false); + pa = VM_PAGE_TO_PHYS(&rv->pages[lo]); + } + if (lo * PAGE_SIZE + size <= hi * PAGE_SIZE) + return (true); + lo = hi; + } + if (++i < n) + changes = rv->popmap[i]; + else if (i == n) + changes = bits_left == 0 ? -1UL : + (rv->popmap[n] | (-1UL << bits_left)); + else + return (false); + } +} + +/* * Searches the partially populated reservation queue for the least recently * changed reservation with free pages that satisfy the given request for * contiguous physical memory. If a satisfactory reservation is found, it is - * broken. Returns TRUE if a reservation is broken and FALSE otherwise. + * broken. Returns true if a reservation is broken and false otherwise. * * The free page queue lock must be held. */ @@ -1180,21 +1259,19 @@ vm_reserv_reclaim_contig(int domain, u_long npages, vm { vm_paddr_t pa, size; vm_reserv_t rv, rvn; - int hi, i, lo, low_index, next_free; if (npages > VM_LEVEL_0_NPAGES - 1) - return (FALSE); + return (false); size = npages << PAGE_SHIFT; vm_reserv_domain_lock(domain); again: for (rv = TAILQ_FIRST(&vm_rvq_partpop[domain]); rv != NULL; rv = rvn) { rvn = TAILQ_NEXT(rv, partpopq); - pa = VM_PAGE_TO_PHYS(&rv->pages[VM_LEVEL_0_NPAGES - 1]); - if (pa + PAGE_SIZE - size < low) { + pa = VM_PAGE_TO_PHYS(&rv->pages[0]); + if (pa + VM_LEVEL_0_SIZE - size < low) { /* This entire reservation is too low; go to next. */ continue; } - pa = VM_PAGE_TO_PHYS(&rv->pages[0]); if (pa + size > high) { /* This entire reservation is too high; go to next. */ continue; @@ -1210,73 +1287,19 @@ again: } } else vm_reserv_domain_unlock(domain); - if (pa < low) { - /* Start the search for free pages at "low". */ - low_index = (low + PAGE_MASK - pa) >> PAGE_SHIFT; - i = low_index / NBPOPMAP; - hi = low_index % NBPOPMAP; - } else - i = hi = 0; - do { - /* Find the next free page. */ - lo = ffsl(~(((1UL << hi) - 1) | rv->popmap[i])); - while (lo == 0 && ++i < NPOPMAP) - lo = ffsl(~rv->popmap[i]); - if (i == NPOPMAP) - break; - /* Convert from ffsl() to ordinary bit numbering. */ - lo--; - next_free = NBPOPMAP * i + lo; - pa = VM_PAGE_TO_PHYS(&rv->pages[next_free]); - KASSERT(pa >= low, - ("vm_reserv_reclaim_contig: pa is too low")); - if (pa + size > high) { - /* The rest of this reservation is too high. */ - break; - } else if ((pa & (alignment - 1)) != 0 || - ((pa ^ (pa + size - 1)) & ~(boundary - 1)) != 0) { - /* - * The current page doesn't meet the alignment - * and/or boundary requirements. Continue - * searching this reservation until the rest - * of its free pages are either excluded or - * exhausted. - */ - hi = lo + 1; - if (hi >= NBPOPMAP) { - hi = 0; - i++; - } - continue; - } - /* Find the next used page. */ - hi = ffsl(rv->popmap[i] & ~((1UL << lo) - 1)); - while (hi == 0 && ++i < NPOPMAP) { - if ((NBPOPMAP * i - next_free) * PAGE_SIZE >= - size) { - vm_reserv_reclaim(rv); - vm_reserv_unlock(rv); - return (TRUE); - } - hi = ffsl(rv->popmap[i]); - } - /* Convert from ffsl() to ordinary bit numbering. */ - if (i != NPOPMAP) - hi--; - if ((NBPOPMAP * i + hi - next_free) * PAGE_SIZE >= - size) { - vm_reserv_reclaim(rv); - vm_reserv_unlock(rv); - return (TRUE); - } - } while (i < NPOPMAP); + if (vm_reserv_test_contig(rv, npages, low, high, + alignment, boundary)) { + vm_reserv_reclaim(rv); + vm_reserv_unlock(rv); + return (true); + } vm_reserv_unlock(rv); vm_reserv_domain_lock(domain); if (rvn != NULL && !rvn->inpartpopq) goto again; } vm_reserv_domain_unlock(domain); - return (FALSE); + return (false); } /* _______________________________________________ svn-src-head@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/svn-src-head To unsubscribe, send any mail to "svn-src-head-unsubscr...@freebsd.org"
