From: Mike Rapoport <email@example.com> To: Alexander Duyck <firstname.lastname@example.org> Cc: Michal Hocko <email@example.com>, firstname.lastname@example.org, email@example.com, firstname.lastname@example.org, email@example.com, firstname.lastname@example.org, email@example.com, firstname.lastname@example.org, email@example.com, firstname.lastname@example.org, email@example.com, firstname.lastname@example.org, email@example.com, firstname.lastname@example.org, email@example.com, firstname.lastname@example.org, email@example.com, firstname.lastname@example.org, email@example.com Subject: Re: [mm PATCH v5 0/7] Deferred page init improvements Date: Wed, 14 Nov 2018 17:55:12 -0800 Message-ID: <20181115015511.GB2353@rapoport-lnx> (raw) In-Reply-To: <firstname.lastname@example.org> On Wed, Nov 14, 2018 at 04:50:23PM -0800, Alexander Duyck wrote: > > > On 11/14/2018 7:07 AM, Michal Hocko wrote: > >On Mon 05-11-18 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. > >> > >>I have called out the improvement observed with each patch. > > > >I have only glanced through the code (there is a lot of the code to look > >at here). And I do not like the code duplication and the way how you > >make the hotplug special. There shouldn't be any real reason for that > >IMHO (e.g. why do we init pfn-at-a-time in early init while we do > >pageblock-at-a-time for hotplug). I might be wrong here and the code > >reuse might be really hard to achieve though. > > Actually it isn't so much that hotplug is special. The issue is more that > the non-hotplug case is special in that you have to perform a number of > extra checks for things that just aren't necessary for the hotplug case. > > If anything I would probably need a new iterator that would be able to take > into account all the checks for the non-hotplug case and then provide ranges > of PFNs to initialize. > > >I am also not impressed by new iterators because this api is quite > >complex already. But this is mostly a detail. > > Yeah, the iterators were mostly an attempt at hiding some of the complexity. > Being able to break a loop down to just an iterator provding the start of > the range and the number of elements to initialize is pretty easy to > visualize, or at least I thought so. Just recently we had a discussion about overlapping for_each_mem_range() and for_each_mem_pfn_range(), but unfortunately it appears that no mailing list was cc'ed by the original patch author :( In short, there was a spelling fix in one of them and Michal pointed out that their functionality overlaps. I have no objection for for_each_free_mem_pfn_range_in_zone() and __next_mem_pfn_range_in_zone(), but probably we should consider unifying the older iterators before we introduce a new one? > >Thing I do not like is that you keep microptimizing PageReserved part > >while there shouldn't be anything fundamental about it. We should just > >remove it rather than make the code more complex. I fell more and more > >guilty to add there actually. > > I plan to remove it, but don't think I can get to it in this patch set. > > I was planning to submit one more iteration of this patch set early next > week, and then start focusing more on the removal of the PageReserved bit > for hotplug. I figure it is probably going to be a full patch set onto > itself and as you pointed out at the start of this email there is already > enough code to review without adding that. > > -- Sincerely yours, Mike.
next prev parent reply index Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top 2018-11-05 21:19 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 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 [this message] 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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