Re: [v6 14/15] mm: optimize early system hash allocations

Michal Hocko
2017-08-11T13:05:47Z

On Mon 07-08-17 16:38:48, Pavel Tatashin wrote:
> Clients can call alloc_large_system_hash() with flag: HASH_ZERO to specify
> that memory that was allocated for system hash needs to be zeroed,
> otherwise the memory does not need to be zeroed, and client will initialize
> it.
>
> If memory does not need to be zero'd, call the new
> memblock_virt_alloc_raw() interface, and thus improve the boot performance.
>
> Signed-off-by: Pavel Tatashin <pasha.tatashin@oracle.com>
> Reviewed-by: Steven Sistare <steven.sistare@oracle.com>
> Reviewed-by: Daniel Jordan <daniel.m.jordan@oracle.com>
> Reviewed-by: Bob Picco <bob.picco@oracle.com>

OK, but as mentioned in the previous patch add memblock_virt_alloc_raw
in this patch.

Acked-by: Michal Hocko <mhocko@suse.com>

> ---
> mm/page_alloc.c | 15 +++++++--------
> 1 file changed, 7 insertions(+), 8 deletions(-)
>
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 4d32c1fa4c6c..000806298dfb 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -7354,18 +7354,17 @@ void *__init alloc_large_system_hash(const char *tablename,
>
> log2qty = ilog2(numentries);
>
> - /*
> - * memblock allocator returns zeroed memory already, so HASH_ZERO is
> - * currently not used when HASH_EARLY is specified.
> - */
> gfp_flags = (flags & HASH_ZERO) ? GFP_ATOMIC | __GFP_ZERO : GFP_ATOMIC;
> do {
> size = bucketsize << log2qty;
> - if (flags & HASH_EARLY)
> - table = memblock_virt_alloc_nopanic(size, 0);
> - else if (hashdist)
> + if (flags & HASH_EARLY) {
> + if (flags & HASH_ZERO)
> + table = memblock_virt_alloc_nopanic(size, 0);
> + else
> + table = memblock_virt_alloc_raw(size, 0);
> + } else if (hashdist) {
> table = __vmalloc(size, gfp_flags, PAGE_KERNEL);
> - else {
> + } else {
> /*
> * If bucketsize is not a power-of-two, we may free
> * some pages at the end of hash table which
> --
> 2.14.0

--
Michal Hocko
SUSE Labs