On Mon, Apr 13, 2015 at 04:04:45PM -0400, Jung-uk Kim wrote:
> Please try the attached patch.
>
> Jung-uk Kim
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> Index: sys/amd64/amd64/pmap.c
> ===================================================================
> --- sys/amd64/amd64/pmap.c (revision 281496)
> +++ sys/amd64/amd64/pmap.c (working copy)
> @@ -412,7 +412,7 @@ static caddr_t crashdumpmap;
> static void free_pv_chunk(struct pv_chunk *pc);
> static void free_pv_entry(pmap_t pmap, pv_entry_t pv);
> static pv_entry_t get_pv_entry(pmap_t pmap, struct rwlock **lockp);
> -static int popcnt_pc_map_elem_pq(uint64_t elem);
> +static int popcnt_pc_map(uint64_t *pc_map);
> static vm_page_t reclaim_pv_chunk(pmap_t locked_pmap, struct rwlock **lockp);
> static void reserve_pv_entries(pmap_t pmap, int needed,
> struct rwlock **lockp);
> @@ -2979,7 +2979,7 @@ retry:
> }
>
> /*
> - * Returns the number of one bits within the given PV chunk map element.
> + * Returns the number of one bits within the given PV chunk map.
> *
> * The erratas for Intel processors state that "POPCNT Instruction May
> * Take Longer to Execute Than Expected". It is believed that the
> @@ -2994,12 +2994,21 @@ retry:
> * 5th Gen Core: BDM85
> */
> static int
> -popcnt_pc_map_elem_pq(uint64_t elem)
> +popcnt_pc_map(uint64_t *pc_map)
> {
> - u_long result;
> + u_long count, result;
> + int field;
>
> - __asm __volatile("xorl %k0,%k0;popcntq %1,%0"
> - : "=&r" (result) : "rm" (elem));
> + result = 0;
> + if ((cpu_feature2 & CPUID2_POPCNT) != 0)
> + for (field = 0; field < _NPCM; field++) {
> + __asm __volatile("xorl %k0, %k0; popcntq %1, %0"
> + : "=r" (count) : "m" (pc_map[field]));
> + result += count;
> + }
> + else
> + for (field = 0; field < _NPCM; field++)
> + result += bitcount64(pc_map[field]);
> return (result);
> }
>
> @@ -3031,15 +3040,7 @@ reserve_pv_entries(pmap_t pmap, int needed, struct
> retry:
> avail = 0;
> TAILQ_FOREACH(pc, &pmap->pm_pvchunk, pc_list) {
> - if ((cpu_feature2 & CPUID2_POPCNT) == 0) {
> - free = bitcount64(pc->pc_map[0]);
> - free += bitcount64(pc->pc_map[1]);
> - free += bitcount64(pc->pc_map[2]);
> - } else {
> - free = popcnt_pc_map_elem_pq(pc->pc_map[0]);
> - free += popcnt_pc_map_elem_pq(pc->pc_map[1]);
> - free += popcnt_pc_map_elem_pq(pc->pc_map[2]);
> - }
> + free = popcnt_pc_map(pc->pc_map);
> if (free == 0)
> break;
> avail += free;
Yes, this worked for me the same way as for you, the argument is taken
directly from memory, without temporary spill. Is this due to silly
inliner ? Whatever the reason is, I think a comment should be added
noting the subtlety.
Otherwise, looks fine.
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