From: Pavel Tatashin <pasha.tatashin@soleen.com>
To: Alexander Duyck <alexander.h.duyck@linux.intel.com>
Cc: daniel.m.jordan@oracle.com, akpm@linux-foundation.org,
linux-mm@kvack.org, sparclinux@vger.kernel.org,
linux-kernel@vger.kernel.org, linux-nvdimm@lists.01.org,
davem@davemloft.net, pavel.tatashin@microsoft.com,
mhocko@suse.com, mingo@kernel.org,
kirill.shutemov@linux.intel.com, dan.j.williams@intel.com,
dave.jiang@intel.com, rppt@linux.vnet.ibm.com,
willy@infradead.org, vbabka@suse.cz, khalid.aziz@oracle.com,
ldufour@linux.vnet.ibm.com, mgorman@techsingularity.net,
yi.z.zhang@linux.intel.com
Subject: Re: [mm PATCH v5 0/7] Deferred page init improvements
Date: Fri, 9 Nov 2018 20:16:52 -0500 [thread overview]
Message-ID: <20181110011652.2wozbvfimcnhogfj@xakep.localdomain> (raw)
In-Reply-To: <0d8782742d016565870c578848138aaedf873a7c.camel@linux.intel.com>
On 18-11-09 16:46:02, Alexander Duyck wrote:
> On Fri, 2018-11-09 at 19:00 -0500, Pavel Tatashin wrote:
> > On 18-11-09 15:14:35, Alexander Duyck wrote:
> > > On Fri, 2018-11-09 at 16:15 -0500, Pavel Tatashin wrote:
> > > > On 18-11-05 13:19:25, Alexander Duyck wrote:
> > > > > This patchset is essentially a refactor of the page initialization logic
> > > > > that is meant to provide for better code reuse while providing a
> > > > > significant improvement in deferred page initialization performance.
> > > > >
> > > > > In my testing on an x86_64 system with 384GB of RAM and 3TB of persistent
> > > > > memory per node I have seen the following. In the case of regular memory
> > > > > initialization the deferred init time was decreased from 3.75s to 1.06s on
> > > > > average. For the persistent memory the initialization time dropped from
> > > > > 24.17s to 19.12s on average. This amounts to a 253% improvement for the
> > > > > deferred memory initialization performance, and a 26% improvement in the
> > > > > persistent memory initialization performance.
> > > >
> > > > Hi Alex,
> > > >
> > > > Please try to run your persistent memory init experiment with Daniel's
> > > > patches:
> > > >
> > > > https://lore.kernel.org/lkml/20181105165558.11698-1-daniel.m.jordan@oracle.com/
> > >
> > > I've taken a quick look at it. It seems like a bit of a brute force way
> > > to try and speed things up. I would be worried about it potentially
> >
> > There is a limit to max number of threads that ktasks start. The memory
> > throughput is *much* higher than what one CPU can maxout in a node, so
> > there is no reason to leave the other CPUs sit idle during boot when
> > they can help to initialize.
>
> Right, but right now that limit can still be pretty big when it is
> something like 25% of all the CPUs on a 288 CPU system.
It is still OK. About 9 threads per node.
That machine has 1T of memory, which means 8 nodes need to initialize 2G
of memory each. With 46G/s throughout it should take 0.043s Which is 10
times higher than what Daniel sees with 0.325s, so there is still room
to saturate the memory throughput.
Now, if the multi-threadding efficiency is good, it should take
1.261s / 9 threads = 0.14s
>
> One issue is the way the code was ends up essentially blowing out the
> cache over and over again. Doing things in two passes made it really
> expensive as you took one cache miss to initialize it, and another to
> free it. I think getting rid of that is one of the biggest gains with
> my patch set.
I am not arguing that your patches make sense, all I am saying that
ktasks improve time order of magnitude better on machines with large
amount of memory.
Pasha
next prev parent reply other threads:[~2018-11-10 1:17 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-05 21:19 [mm PATCH v5 0/7] Deferred page init improvements Alexander Duyck
2018-11-05 21:19 ` [mm PATCH v5 1/7] mm: Use mm_zero_struct_page from SPARC on all 64b architectures Alexander Duyck
2018-11-05 21:19 ` [mm PATCH v5 2/7] mm: Drop meminit_pfn_in_nid as it is redundant Alexander Duyck
2018-11-05 21:19 ` [mm PATCH v5 3/7] mm: Implement new zone specific memblock iterator Alexander Duyck
2018-11-09 23:26 ` Pavel Tatashin
2018-11-09 23:58 ` Alexander Duyck
2018-11-10 0:11 ` Pavel Tatashin
2018-11-05 21:19 ` [mm PATCH v5 4/7] mm: Initialize MAX_ORDER_NR_PAGES at a time instead of doing larger sections Alexander Duyck
2018-11-10 1:02 ` Pavel Tatashin
2018-11-19 18:53 ` Alexander Duyck
2018-11-05 21:19 ` [mm PATCH v5 5/7] mm: Move hot-plug specific memory init into separate functions and optimize Alexander Duyck
2018-11-10 2:07 ` Pavel Tatashin
2018-11-05 21:19 ` [mm PATCH v5 6/7] mm: Add reserved flag setting to set_page_links Alexander Duyck
2018-11-10 2:11 ` Pavel Tatashin
2018-11-05 21:20 ` [mm PATCH v5 7/7] mm: Use common iterator for deferred_init_pages and deferred_free_pages Alexander Duyck
2018-11-10 4:13 ` Pavel Tatashin
2018-11-12 15:12 ` Alexander Duyck
2018-11-09 21:15 ` [mm PATCH v5 0/7] Deferred page init improvements Pavel Tatashin
2018-11-09 23:14 ` Alexander Duyck
2018-11-10 0:00 ` Pavel Tatashin
2018-11-10 0:46 ` Alexander Duyck
2018-11-10 1:16 ` Pavel Tatashin [this message]
2018-11-12 19:10 ` Alexander Duyck
2018-11-12 20:37 ` Pavel Tatashin
2018-11-12 16:25 ` Daniel Jordan
2018-11-14 15:07 ` Michal Hocko
2018-11-14 19:12 ` Pavel Tatashin
2018-11-14 21:35 ` Michal Hocko
2018-11-15 0:50 ` Alexander Duyck
2018-11-15 1:55 ` Mike Rapoport
2018-11-15 19:09 ` Mike Rapoport
2018-11-15 8:10 ` Michal Hocko
2018-11-15 16:02 ` Alexander Duyck
2018-11-15 16:40 ` Michal Hocko
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