On Sun, Apr 14, 2024 at 12:45:26AM +0000, Wei Yang wrote: > Current memblock_add_range() does the insertion with two round > iteration. > > First round does the calculation of new region required, and second > round does the actual insertion. Between them, if current max can't meet > new region requirement, it is expanded. > > The worst case is: > > 1. cnt == max > 2. new range overlaps all existing region > > This means the final cnt should be (2 * max + 1). Since we always double > the array size, this means we only need to double the array twice at the > worst case, which is fairly rare. For other cases, only once array > double is enough. > > Let's double the array immediately when there is no room for new region. > This simplify the code a little. Very similar patch was posted a while ago: https://lore.kernel.org/all/20221025070943.363578-1-yajun.deng@xxxxxxxxx and it caused boot regression: https://lore.kernel.org/linux-mm/Y2oLYB7Tu7J91tVm@xxxxxxxxxxxxx > Signed-off-by: Wei Yang <richard.weiyang@xxxxxxxxx> > CC: Jinyu Tang <tjytimi@xxxxxxx> > CC: Peng Zhang <zhangpeng.00@xxxxxxxxxxxxx> > --- > mm/memblock.c | 74 +++++++++++++++------------------------------------ > 1 file changed, 22 insertions(+), 52 deletions(-) > > diff --git a/mm/memblock.c b/mm/memblock.c > index 98d25689cf10..b46109300927 100644 > --- a/mm/memblock.c > +++ b/mm/memblock.c > @@ -585,10 +585,9 @@ static int __init_memblock memblock_add_range(struct memblock_type *type, > phys_addr_t base, phys_addr_t size, > int nid, enum memblock_flags flags) > { > - bool insert = false; > phys_addr_t obase = base; > phys_addr_t end = base + memblock_cap_size(base, &size); > - int idx, nr_new, start_rgn = -1, end_rgn; > + int idx, start_rgn = -1, end_rgn; > struct memblock_region *rgn; > > if (!size) > @@ -606,25 +605,6 @@ static int __init_memblock memblock_add_range(struct memblock_type *type, > return 0; > } > > - /* > - * The worst case is when new range overlaps all existing regions, > - * then we'll need type->cnt + 1 empty regions in @type. So if > - * type->cnt * 2 + 1 is less than or equal to type->max, we know > - * that there is enough empty regions in @type, and we can insert > - * regions directly. > - */ > - if (type->cnt * 2 + 1 <= type->max) > - insert = true; > - > -repeat: > - /* > - * The following is executed twice. Once with %false @insert and > - * then with %true. The first counts the number of regions needed > - * to accommodate the new area. The second actually inserts them. > - */ > - base = obase; > - nr_new = 0; > - > for_each_memblock_type(idx, type, rgn) { > phys_addr_t rbase = rgn->base; > phys_addr_t rend = rbase + rgn->size; > @@ -642,15 +622,17 @@ static int __init_memblock memblock_add_range(struct memblock_type *type, > WARN_ON(nid != memblock_get_region_node(rgn)); > #endif > WARN_ON(flags != rgn->flags); > - nr_new++; > - if (insert) { > - if (start_rgn == -1) > - start_rgn = idx; > - end_rgn = idx + 1; > - memblock_insert_region(type, idx++, base, > - rbase - base, nid, > - flags); > + if (type->cnt >= type->max) { > + if (memblock_double_array(type, obase, size) < 0) > + return -ENOMEM; > } > + > + if (start_rgn == -1) > + start_rgn = idx; > + end_rgn = idx + 1; > + memblock_insert_region(type, idx++, base, > + rbase - base, nid, > + flags); > } > /* area below @rend is dealt with, forget about it */ > base = min(rend, end); > @@ -658,33 +640,21 @@ static int __init_memblock memblock_add_range(struct memblock_type *type, > > /* insert the remaining portion */ > if (base < end) { > - nr_new++; > - if (insert) { > - if (start_rgn == -1) > - start_rgn = idx; > - end_rgn = idx + 1; > - memblock_insert_region(type, idx, base, end - base, > - nid, flags); > + if (type->cnt >= type->max) { > + if (memblock_double_array(type, obase, size) < 0) > + return -ENOMEM; > } > - } > > - if (!nr_new) > - return 0; > + if (start_rgn == -1) > + start_rgn = idx; > + end_rgn = idx + 1; > + memblock_insert_region(type, idx, base, end - base, > + nid, flags); > + } > > - /* > - * If this was the first round, resize array and repeat for actual > - * insertions; otherwise, merge and return. > - */ > - if (!insert) { > - while (type->cnt + nr_new > type->max) > - if (memblock_double_array(type, obase, size) < 0) > - return -ENOMEM; > - insert = true; > - goto repeat; > - } else { > + if (start_rgn != -1) > memblock_merge_regions(type, start_rgn, end_rgn); > - return 0; > - } > + return 0; > } > > /** > -- > 2.34.1 > -- Sincerely yours, Mike.
