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

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Message-ID: <20170811130541.GM30811@dhcp22.suse.cz>
Date:   Fri, 11 Aug 2017 15:05:42 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Pavel Tatashin <pasha.tatashin@...cle.com>
Cc:     linux-kernel@...r.kernel.org, sparclinux@...r.kernel.org,
        linux-mm@...ck.org, linuxppc-dev@...ts.ozlabs.org,
        linux-s390@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        x86@...nel.org, kasan-dev@...glegroups.com, borntraeger@...ibm.com,
        heiko.carstens@...ibm.com, davem@...emloft.net,
        willy@...radead.org, ard.biesheuvel@...aro.org,
        will.deacon@....com, catalin.marinas@....com, sam@...nborg.org
Subject: Re: [v6 14/15] mm: optimize early system hash allocations

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@...cle.com>
> Reviewed-by: Steven Sistare <steven.sistare@...cle.com>
> Reviewed-by: Daniel Jordan <daniel.m.jordan@...cle.com>
> Reviewed-by: Bob Picco <bob.picco@...cle.com>

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

Acked-by: Michal Hocko <mhocko@...e.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