Re: [v1 0/5] parallelized "struct page" zeroing

Re: [v1 0/5] parallelized "struct page" zeroing

[Christian Borntraeger]

On 03/24/2017 12:01 AM, Pavel Tatashin wrote:
> When deferred struct page initialization feature is enabled, we get a
> performance gain of initializing vmemmap in parallel after other CPUs are
> started. However, we still zero the memory for vmemmap using one boot CPU.
> This patch-set fixes the memset-zeroing limitation by deferring it as well.
> 
> Here is example performance gain on SPARC with 32T:
> base
> https://hastebin.com/ozanelatat.go
> 
> fix
> https://hastebin.com/utonawukof.go
> 
> As you can see without the fix it takes: 97.89s to boot
> With the fix it takes: 46.91 to boot.
> 
> On x86 time saving is going to be even greater (proportionally to memory size)
> because there are twice as many "struct page"es for the same amount of memory,
> as base pages are twice smaller.

Fixing the linux-s390 mailing list email.
This might be useful for s390 as well.

> 
> 
> Pavel Tatashin (5):
>   sparc64: simplify vmemmap_populate
>   mm: defining memblock_virt_alloc_try_nid_raw
>   mm: add "zero" argument to vmemmap allocators
>   mm: zero struct pages during initialization
>   mm: teach platforms not to zero struct pages memory
> 
>  arch/powerpc/mm/init_64.c |    4 +-
>  arch/s390/mm/vmem.c       |    5 ++-
>  arch/sparc/mm/init_64.c   |   26 +++++++----------------
>  arch/x86/mm/init_64.c     |    3 +-
>  include/linux/bootmem.h   |    3 ++
>  include/linux/mm.h        |   15 +++++++++++--
>  mm/memblock.c             |   46 ++++++++++++++++++++++++++++++++++++------
>  mm/page_alloc.c           |    3 ++
>  mm/sparse-vmemmap.c       |   48 +++++++++++++++++++++++++++++---------------
>  9 files changed, 103 insertions(+), 50 deletions(-)
> 


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Re: [v1 0/5] parallelized "struct page" zeroing

[Heiko Carstens]

On Fri, Mar 24, 2017 at 09:51:09AM +0100, Christian Borntraeger wrote:
> On 03/24/2017 12:01 AM, Pavel Tatashin wrote:
> > When deferred struct page initialization feature is enabled, we get a
> > performance gain of initializing vmemmap in parallel after other CPUs are
> > started. However, we still zero the memory for vmemmap using one boot CPU.
> > This patch-set fixes the memset-zeroing limitation by deferring it as well.
> > 
> > Here is example performance gain on SPARC with 32T:
> > base
> > https://hastebin.com/ozanelatat.go
> > 
> > fix
> > https://hastebin.com/utonawukof.go
> > 
> > As you can see without the fix it takes: 97.89s to boot
> > With the fix it takes: 46.91 to boot.
> > 
> > On x86 time saving is going to be even greater (proportionally to memory size)
> > because there are twice as many "struct page"es for the same amount of memory,
> > as base pages are twice smaller.
> 
> Fixing the linux-s390 mailing list email.
> This might be useful for s390 as well.

Unfortunately only for the fake numa case, since as far as I understand it,
parallelization happens only on a node granularity. And since we are
usually only having one node...

But anyway, it won't hurt to set ARCH_SUPPORTS_DEFERRED_STRUCT_PAGE_INIT on
s390 also. I'll do some testing and then we'll see.

Pavel, could you please change your patch 5 so it also converts the s390
call sites of vmemmap_alloc_block() so they use VMEMMAP_ZERO instead of
'true' as argument?

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