linux-kernel - Re: [PATCH v7 07/11] sparc64: optimized struct page zeroing

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Date:   Tue, 29 Aug 2017 18:12:08 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     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, willy@...radead.org, mhocko@...nel.org,
        ard.biesheuvel@...aro.org, will.deacon@....com,
        catalin.marinas@....com, sam@...nborg.org,
        mgorman@...hsingularity.net, Steven.Sistare@...cle.com,
        daniel.m.jordan@...cle.com, bob.picco@...cle.com
Subject: Re: [PATCH v7 07/11] sparc64: optimized struct page zeroing

From: Pavel Tatashin <pasha.tatashin@...cle.com>
Date: Mon, 28 Aug 2017 22:02:18 -0400

> Add an optimized mm_zero_struct_page(), so struct page's are zeroed without
> calling memset(). We do eight to ten regular stores based on the size of
> struct page. Compiler optimizes out the conditions of switch() statement.
> 
> SPARC-M6 with 15T of memory, single thread performance:
> 
>                                BASE            FIX  OPTIMIZED_FIX
>         bootmem_init   28.440467985s   2.305674818s   2.305161615s
> free_area_init_nodes  202.845901673s 225.343084508s 172.556506560s
>                       --------------------------------------------
> Total                 231.286369658s 227.648759326s 174.861668175s
> 
> BASE:  current linux
> FIX:   This patch series without "optimized struct page zeroing"
> OPTIMIZED_FIX: This patch series including the current patch.
> 
> bootmem_init() is where memory for struct pages is zeroed during
> allocation. Note, about two seconds in this function is a fixed time: it
> does not increase as memory is increased.
> 
> 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>

You should probably use initializing stores when you are doing 8
stores and we thus know the page struct is cache line aligned.

But other than that:

Acked-by: David S. Miller <davem@...emloft.net>