From: Pasha Tatashin <pasha.tatashin@oracle.com>
To: Michal Hocko <mhocko@kernel.org>
Cc: linux-kernel@vger.kernel.org, sparclinux@vger.kernel.org,
linux-mm@kvack.org, linuxppc-dev@lists.ozlabs.org,
linux-s390@vger.kernel.org, borntraeger@de.ibm.com,
heiko.carstens@de.ibm.com, davem@davemloft.net
Subject: Re: [v3 0/9] parallelized "struct page" zeroing
Date: Tue, 9 May 2017 14:54:50 -0400 [thread overview]
Message-ID: <fae4a92c-e78c-32cb-606a-8e5087acb13f@oracle.com> (raw)
In-Reply-To: <20170509181234.GA4397@dhcp22.suse.cz>
Hi Michal,
> I like the idea of postponing the zeroing from the allocation to the
> init time. To be honest the improvement looks much larger than I would
> expect (Btw. this should be a part of the changelog rather than a
> outside link).
The improvements are larger, because this time was never measured, as
Linux does not have early boot time stamps. I added them for x86 and
SPARC to emasure the performance. I am pushing those changes through
separate patchsets.
>
> The implementation just looks too large to what I would expect. E.g. do
> we really need to add zero argument to the large part of the memblock
> API? Wouldn't it be easier to simply export memblock_virt_alloc_internal
> (or its tiny wrapper memblock_virt_alloc_core) and move the zeroing
> outside to its 2 callers? A completely untested scratched version at the
> end of the email.
I am OK, with this change. But, I do not really see a difference between:
memblock_virt_alloc_raw()
and
memblock_virt_alloc_core()
In both cases we use memblock_virt_alloc_internal(), but the only
difference is that in my case we tell memblock_virt_alloc_internal() to
zero the pages if needed, and in your case the other two callers are
zeroing it. I like moving memblock_dbg() inside
memblock_virt_alloc_internal()
>
> Also it seems that this is not 100% correct either as it only cares
> about VMEMMAP while DEFERRED_STRUCT_PAGE_INIT might be enabled also for
> SPARSEMEM. This would suggest that we would zero out pages twice,
> right?
Thank you, I will check this combination before sending out the next patch.
>
> A similar concern would go to the memory hotplug patch which will
> fall back to the slab/page allocator IIRC. On the other hand
> __init_single_page is shared with the hotplug code so again we would
> initialize 2 times.
Correct, when memory it hotplugged, to gain the benefit of this fix, and
also not to regress by actually double zeroing "struct pages" we should
not zero it out. However, I do not really have means to test it.
>
> So I suspect more changes are needed. I will have a closer look tomorrow.
Thank you for reviewing this work. I will wait for your comments before
sending out updated patches.
Pasha
next prev parent reply other threads:[~2017-05-09 18:55 UTC|newest]
Thread overview: 46+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-05-05 17:03 [v3 0/9] parallelized "struct page" zeroing Pavel Tatashin
2017-05-05 17:03 ` [v3 1/9] sparc64: simplify vmemmap_populate Pavel Tatashin
2017-05-05 17:03 ` [v3 2/9] mm: defining memblock_virt_alloc_try_nid_raw Pavel Tatashin
2017-05-05 17:03 ` [v3 3/9] mm: add "zero" argument to vmemmap allocators Pavel Tatashin
2017-05-13 19:17 ` kbuild test robot
2017-05-05 17:03 ` [v3 4/9] mm: do not zero vmemmap_buf Pavel Tatashin
2017-05-05 17:03 ` [v3 5/9] mm: zero struct pages during initialization Pavel Tatashin
2017-05-05 17:03 ` [v3 6/9] sparc64: teach sparc not to zero struct pages memory Pavel Tatashin
2017-05-05 17:03 ` [v3 7/9] x86: teach x86 " Pavel Tatashin
2017-05-05 17:03 ` [v3 8/9] powerpc: teach platforms " Pavel Tatashin
2017-05-05 17:03 ` [v3 9/9] s390: " Pavel Tatashin
2017-05-08 11:36 ` Heiko Carstens
2017-05-15 18:24 ` Pasha Tatashin
2017-05-15 23:17 ` Heiko Carstens
2017-05-16 0:33 ` Pasha Tatashin
2017-05-09 18:12 ` [v3 0/9] parallelized "struct page" zeroing Michal Hocko
2017-05-09 18:54 ` Pasha Tatashin [this message]
2017-05-10 7:24 ` Michal Hocko
2017-05-10 13:42 ` Pasha Tatashin
2017-05-10 14:57 ` Michal Hocko
2017-05-10 15:01 ` Pasha Tatashin
2017-05-10 15:20 ` David Miller
2017-05-11 20:47 ` Pasha Tatashin
2017-05-11 20:59 ` Pasha Tatashin
2017-05-12 16:57 ` David Miller
2017-05-12 17:24 ` Pasha Tatashin
2017-05-12 17:37 ` David Miller
2017-05-16 23:50 ` Benjamin Herrenschmidt
2017-05-12 16:56 ` David Miller
2017-05-10 15:19 ` David Miller
2017-05-10 17:17 ` Matthew Wilcox
2017-05-10 18:00 ` David Miller
2017-05-10 21:11 ` Matthew Wilcox
2017-05-11 8:05 ` Michal Hocko
2017-05-11 14:35 ` David Miller
2017-05-15 18:12 ` Pasha Tatashin
2017-05-15 19:38 ` Michal Hocko
2017-05-15 20:44 ` Pasha Tatashin
2017-05-16 8:36 ` Michal Hocko
2017-05-26 16:45 ` Pasha Tatashin
2017-05-29 11:53 ` Michal Hocko
2017-05-30 17:16 ` Pasha Tatashin
2017-05-31 16:31 ` Michal Hocko
2017-05-31 16:51 ` David Miller
2017-06-01 3:35 ` Pasha Tatashin
2017-06-01 8:46 ` Michal Hocko
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