From: Joao Martins <joao.m.martins@oracle.com> To: Jason Gunthorpe <jgg@ziepe.ca> Cc: linux-mm@kvack.org, linux-nvdimm@lists.01.org, Matthew Wilcox <willy@infradead.org>, Muchun Song <songmuchun@bytedance.com>, Mike Kravetz <mike.kravetz@oracle.com>, Andrew Morton <akpm@linux-foundation.org> Subject: Re: [PATCH RFC 9/9] mm: Add follow_devmap_page() for devdax vmas Date: Wed, 9 Dec 2020 11:19:04 +0000 [thread overview] Message-ID: <7cf4de6b-5377-394b-d95a-586e6422b9cd@oracle.com> (raw) In-Reply-To: <20201208195754.GR5487@ziepe.ca> On 12/8/20 7:57 PM, Jason Gunthorpe wrote: > On Tue, Dec 08, 2020 at 05:29:01PM +0000, Joao Martins wrote: >> Similar to follow_hugetlb_page() add a follow_devmap_page which rather >> than calling follow_page() per 4K page in a PMD/PUD it does so for the >> entire PMD, where we lock the pmd/pud, get all pages , unlock. >> >> While doing so, we only change the refcount once when PGMAP_COMPOUND is >> passed in. >> >> This let us improve {pin,get}_user_pages{,_longterm}() considerably: >> >> $ gup_benchmark -f /dev/dax0.2 -m 16384 -r 10 -S [-U,-b,-L] -n 512 -w >> >> (<test>) [before] -> [after] >> (get_user_pages 2M pages) ~150k us -> ~8.9k us >> (pin_user_pages 2M pages) ~192k us -> ~9k us >> (pin_user_pages_longterm 2M pages) ~200k us -> ~19k us >> >> Signed-off-by: Joao Martins <joao.m.martins@oracle.com> >> --- >> I've special-cased this to device-dax vmas given its similar page size >> guarantees as hugetlbfs, but I feel this is a bit wrong. I am >> replicating follow_hugetlb_page() as RFC ought to seek feedback whether >> this should be generalized if no fundamental issues exist. In such case, >> should I be changing follow_page_mask() to take either an array of pages >> or a function pointer and opaque arguments which would let caller pick >> its structure? > > I would be extremely sad if this was the only way to do this :( > > We should be trying to make things more general. Yeap, indeed. Specially, when similar problem is observed for THP, at least from the measurements I saw. It is all slow, except for hugetlbfs. > The > hmm_range_fault_path() doesn't have major special cases for device, I > am struggling to understand why gup fast and slow do. > > What we've talked about is changing the calling convention across all > of this to something like: > > struct gup_output { > struct page **cur; > struct page **end; > unsigned long vaddr; > [..] > } > > And making the manipulator like you saw for GUP common: > > gup_output_single_page() > gup_output_pages() > > Then putting this eveywhere. This is the pattern that we ended up with > in hmm_range_fault, and it seems to be working quite well. > > fast/slow should be much more symmetric in code than they are today, > IMHO.. Thanks for the suggestions above. I think those differences mainly exist because it used to be > siloed in arch code. Some of the differences might be bugs, we've seen > that a few times at least.. Interesting, wasn't aware of the siloing. I'll go investigate how this all refactoring goes together, at the point of which a future iteration of this particular patch probably needs to move independently from this series. Joao _______________________________________________ Linux-nvdimm mailing list -- linux-nvdimm@lists.01.org To unsubscribe send an email to linux-nvdimm-leave@lists.01.org
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From: Joao Martins <joao.m.martins@oracle.com> To: Jason Gunthorpe <jgg@ziepe.ca> Cc: linux-mm@kvack.org, Dan Williams <dan.j.williams@intel.com>, Ira Weiny <ira.weiny@intel.com>, linux-nvdimm@lists.01.org, Matthew Wilcox <willy@infradead.org>, Jane Chu <jane.chu@oracle.com>, Muchun Song <songmuchun@bytedance.com>, Mike Kravetz <mike.kravetz@oracle.com>, Andrew Morton <akpm@linux-foundation.org> Subject: Re: [PATCH RFC 9/9] mm: Add follow_devmap_page() for devdax vmas Date: Wed, 9 Dec 2020 11:19:04 +0000 [thread overview] Message-ID: <7cf4de6b-5377-394b-d95a-586e6422b9cd@oracle.com> (raw) In-Reply-To: <20201208195754.GR5487@ziepe.ca> On 12/8/20 7:57 PM, Jason Gunthorpe wrote: > On Tue, Dec 08, 2020 at 05:29:01PM +0000, Joao Martins wrote: >> Similar to follow_hugetlb_page() add a follow_devmap_page which rather >> than calling follow_page() per 4K page in a PMD/PUD it does so for the >> entire PMD, where we lock the pmd/pud, get all pages , unlock. >> >> While doing so, we only change the refcount once when PGMAP_COMPOUND is >> passed in. >> >> This let us improve {pin,get}_user_pages{,_longterm}() considerably: >> >> $ gup_benchmark -f /dev/dax0.2 -m 16384 -r 10 -S [-U,-b,-L] -n 512 -w >> >> (<test>) [before] -> [after] >> (get_user_pages 2M pages) ~150k us -> ~8.9k us >> (pin_user_pages 2M pages) ~192k us -> ~9k us >> (pin_user_pages_longterm 2M pages) ~200k us -> ~19k us >> >> Signed-off-by: Joao Martins <joao.m.martins@oracle.com> >> --- >> I've special-cased this to device-dax vmas given its similar page size >> guarantees as hugetlbfs, but I feel this is a bit wrong. I am >> replicating follow_hugetlb_page() as RFC ought to seek feedback whether >> this should be generalized if no fundamental issues exist. In such case, >> should I be changing follow_page_mask() to take either an array of pages >> or a function pointer and opaque arguments which would let caller pick >> its structure? > > I would be extremely sad if this was the only way to do this :( > > We should be trying to make things more general. Yeap, indeed. Specially, when similar problem is observed for THP, at least from the measurements I saw. It is all slow, except for hugetlbfs. > The > hmm_range_fault_path() doesn't have major special cases for device, I > am struggling to understand why gup fast and slow do. > > What we've talked about is changing the calling convention across all > of this to something like: > > struct gup_output { > struct page **cur; > struct page **end; > unsigned long vaddr; > [..] > } > > And making the manipulator like you saw for GUP common: > > gup_output_single_page() > gup_output_pages() > > Then putting this eveywhere. This is the pattern that we ended up with > in hmm_range_fault, and it seems to be working quite well. > > fast/slow should be much more symmetric in code than they are today, > IMHO.. Thanks for the suggestions above. I think those differences mainly exist because it used to be > siloed in arch code. Some of the differences might be bugs, we've seen > that a few times at least.. Interesting, wasn't aware of the siloing. I'll go investigate how this all refactoring goes together, at the point of which a future iteration of this particular patch probably needs to move independently from this series. Joao
next prev parent reply other threads:[~2020-12-09 11:21 UTC|newest] Thread overview: 147+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-12-08 17:28 [PATCH RFC 0/9] mm, sparse-vmemmap: Introduce compound pagemaps Joao Martins 2020-12-08 17:28 ` Joao Martins 2020-12-08 17:28 ` [PATCH RFC 1/9] memremap: add ZONE_DEVICE support for compound pages Joao Martins 2020-12-08 17:28 ` Joao Martins 2020-12-09 5:59 ` John Hubbard 2020-12-09 5:59 ` John Hubbard 2020-12-09 6:33 ` Matthew Wilcox 2020-12-09 6:33 ` Matthew Wilcox 2020-12-09 13:12 ` Joao Martins 2020-12-09 13:12 ` Joao Martins 2021-02-20 1:43 ` Dan Williams 2021-02-20 1:43 ` Dan Williams 2021-02-22 11:24 ` Joao Martins 2021-02-22 11:24 ` Joao Martins 2021-02-22 20:37 ` Dan Williams 2021-02-22 20:37 ` Dan Williams 2021-02-23 15:46 ` Joao Martins 2021-02-23 15:46 ` Joao Martins 2021-02-23 16:50 ` Dan Williams 2021-02-23 16:50 ` Dan Williams 2021-02-23 17:18 ` Joao Martins 2021-02-23 17:18 ` Joao Martins 2021-02-23 18:18 ` Dan Williams 2021-02-23 18:18 ` Dan Williams 2021-03-10 18:12 ` Joao Martins 2021-03-10 18:12 ` Joao Martins 2021-03-12 5:54 ` Dan Williams 2021-03-12 5:54 ` Dan Williams 2021-02-20 1:24 ` Dan Williams 2021-02-20 1:24 ` Dan Williams 2021-02-22 11:09 ` Joao Martins 2021-02-22 11:09 ` Joao Martins 2020-12-08 17:28 ` [PATCH RFC 2/9] sparse-vmemmap: Consolidate arguments in vmemmap section populate Joao Martins 2020-12-08 17:28 ` Joao Martins 2020-12-09 6:16 ` John Hubbard 2020-12-09 6:16 ` John Hubbard 2020-12-09 13:51 ` Joao Martins 2020-12-09 13:51 ` Joao Martins 2021-02-20 1:49 ` Dan Williams 2021-02-20 1:49 ` Dan Williams 2021-02-22 11:26 ` Joao Martins 2021-02-22 11:26 ` Joao Martins 2020-12-08 17:28 ` [PATCH RFC 3/9] sparse-vmemmap: Reuse vmemmap areas for a given mhp_params::align Joao Martins 2020-12-08 17:28 ` Joao Martins 2020-12-08 17:38 ` Joao Martins 2020-12-08 17:38 ` Joao Martins 2020-12-08 17:28 ` [PATCH RFC 3/9] sparse-vmemmap: Reuse vmemmap areas for a given page size Joao Martins 2020-12-08 17:28 ` Joao Martins 2021-02-20 3:34 ` Dan Williams 2021-02-20 3:34 ` Dan Williams 2021-02-22 11:42 ` Joao Martins 2021-02-22 11:42 ` Joao Martins 2021-02-22 22:40 ` Dan Williams 2021-02-22 22:40 ` Dan Williams 2021-02-23 15:46 ` Joao Martins 2021-02-23 15:46 ` Joao Martins 2020-12-08 17:28 ` [PATCH RFC 4/9] mm/page_alloc: Reuse tail struct pages for compound pagemaps Joao Martins 2020-12-08 17:28 ` Joao Martins 2021-02-20 6:17 ` Dan Williams 2021-02-20 6:17 ` Dan Williams 2021-02-22 12:01 ` Joao Martins 2021-02-22 12:01 ` Joao Martins 2020-12-08 17:28 ` [PATCH RFC 5/9] device-dax: Compound pagemap support Joao Martins 2020-12-08 17:28 ` Joao Martins 2020-12-08 17:28 ` [PATCH RFC 6/9] mm/gup: Grab head page refcount once for group of subpages Joao Martins 2020-12-08 17:28 ` Joao Martins 2020-12-08 19:49 ` Jason Gunthorpe 2020-12-09 11:05 ` Joao Martins 2020-12-09 11:05 ` Joao Martins 2020-12-09 15:15 ` Jason Gunthorpe 2020-12-09 16:02 ` Joao Martins 2020-12-09 16:02 ` Joao Martins 2020-12-09 16:24 ` Jason Gunthorpe 2020-12-09 17:27 ` Joao Martins 2020-12-09 17:27 ` Joao Martins 2020-12-09 18:14 ` Matthew Wilcox 2020-12-09 18:14 ` Matthew Wilcox 2020-12-09 19:08 ` Jason Gunthorpe 2020-12-10 15:43 ` Joao Martins 2020-12-10 15:43 ` Joao Martins 2020-12-09 4:40 ` John Hubbard 2020-12-09 4:40 ` John Hubbard 2020-12-09 13:44 ` Joao Martins 2020-12-09 13:44 ` Joao Martins 2020-12-08 17:28 ` [PATCH RFC 7/9] mm/gup: Decrement head page " Joao Martins 2020-12-08 17:28 ` Joao Martins 2020-12-08 19:34 ` Jason Gunthorpe 2020-12-09 5:06 ` John Hubbard 2020-12-09 5:06 ` John Hubbard 2020-12-09 13:43 ` Jason Gunthorpe 2020-12-09 12:17 ` Joao Martins 2020-12-09 12:17 ` Joao Martins 2020-12-17 19:05 ` Joao Martins 2020-12-17 19:05 ` Joao Martins 2020-12-17 20:05 ` Jason Gunthorpe 2020-12-17 22:34 ` Joao Martins 2020-12-17 22:34 ` Joao Martins 2020-12-18 14:25 ` Jason Gunthorpe 2020-12-19 2:06 ` John Hubbard 2020-12-19 2:06 ` John Hubbard 2020-12-19 13:10 ` Joao Martins 2020-12-19 13:10 ` Joao Martins 2020-12-08 17:29 ` [PATCH RFC 8/9] RDMA/umem: batch page unpin in __ib_mem_release() Joao Martins 2020-12-08 17:29 ` Joao Martins 2020-12-08 19:29 ` Jason Gunthorpe 2020-12-09 10:59 ` Joao Martins 2020-12-09 10:59 ` Joao Martins 2020-12-19 13:15 ` Joao Martins 2020-12-19 13:15 ` Joao Martins 2020-12-09 5:18 ` John Hubbard 2020-12-09 5:18 ` John Hubbard 2020-12-08 17:29 ` [PATCH RFC 9/9] mm: Add follow_devmap_page() for devdax vmas Joao Martins 2020-12-08 17:29 ` Joao Martins 2020-12-08 19:57 ` Jason Gunthorpe 2020-12-09 8:05 ` Christoph Hellwig 2020-12-09 8:05 ` Christoph Hellwig 2020-12-09 11:19 ` Joao Martins [this message] 2020-12-09 11:19 ` Joao Martins 2020-12-09 5:23 ` John Hubbard 2020-12-09 5:23 ` John Hubbard 2020-12-09 9:38 ` [PATCH RFC 0/9] mm, sparse-vmemmap: Introduce compound pagemaps David Hildenbrand 2020-12-09 9:38 ` David Hildenbrand 2020-12-09 9:52 ` [External] " Muchun Song 2020-12-09 9:52 ` Muchun Song 2021-02-20 1:18 ` Dan Williams 2021-02-20 1:18 ` Dan Williams 2021-02-22 11:06 ` Joao Martins 2021-02-22 11:06 ` Joao Martins 2021-02-22 14:32 ` Joao Martins 2021-02-22 14:32 ` Joao Martins 2021-02-23 16:28 ` Joao Martins 2021-02-23 16:28 ` Joao Martins 2021-02-23 16:44 ` Dan Williams 2021-02-23 16:44 ` Dan Williams 2021-02-23 17:15 ` Joao Martins 2021-02-23 17:15 ` Joao Martins 2021-02-23 18:15 ` Dan Williams 2021-02-23 18:15 ` Dan Williams 2021-02-23 18:54 ` Jason Gunthorpe 2021-02-23 22:48 ` Dan Williams 2021-02-23 22:48 ` Dan Williams 2021-02-23 23:07 ` Jason Gunthorpe 2021-02-24 0:14 ` Dan Williams 2021-02-24 0:14 ` Dan Williams 2021-02-24 1:00 ` Jason Gunthorpe 2021-02-24 1:32 ` Dan Williams 2021-02-24 1:32 ` Dan Williams
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