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Violators will be prosecuted for from ; Wed, 17 Oct 2018 08:30:56 +0100 Date: Wed, 17 Oct 2018 10:30:46 +0300 From: Mike Rapoport Subject: Re: [mm PATCH v3 1/6] mm: Use mm_zero_struct_page from SPARC on all 64b architectures References: <20181015202456.2171.88406.stgit@localhost.localdomain> <20181015202656.2171.92963.stgit@localhost.localdomain> <57c559f6-4858-7a52-7fbb-979caa08f240@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <57c559f6-4858-7a52-7fbb-979caa08f240@gmail.com> Message-Id: <20181017073045.GA20004@rapoport-lnx> Sender: owner-linux-mm@kvack.org List-ID: To: Pavel Tatashin Cc: Alexander Duyck , linux-mm@kvack.org, akpm@linux-foundation.org, pavel.tatashin@microsoft.com, mhocko@suse.com, dave.jiang@intel.com, linux-kernel@vger.kernel.org, willy@infradead.org, davem@davemloft.net, yi.z.zhang@linux.intel.com, khalid.aziz@oracle.com, rppt@linux.vnet.ibm.com, vbabka@suse.cz, sparclinux@vger.kernel.org, dan.j.williams@intel.com, ldufour@linux.vnet.ibm.com, mgorman@techsingularity.net, mingo@kernel.org, kirill.shutemov@linux.intel.com On Tue, Oct 16, 2018 at 03:01:11PM -0400, Pavel Tatashin wrote: > > > On 10/15/18 4:26 PM, Alexander Duyck wrote: > > This change makes it so that we use the same approach that was already in > > use on Sparc on all the archtectures that support a 64b long. > > > > This is mostly motivated by the fact that 8 to 10 store/move instructions > > are likely always going to be faster than having to call into a function > > that is not specialized for handling page init. > > > > An added advantage to doing it this way is that the compiler can get away > > with combining writes in the __init_single_page call. As a result the > > memset call will be reduced to only about 4 write operations, or at least > > that is what I am seeing with GCC 6.2 as the flags, LRU poitners, and > > count/mapcount seem to be cancelling out at least 4 of the 8 assignments on > > my system. > > > > One change I had to make to the function was to reduce the minimum page > > size to 56 to support some powerpc64 configurations. > > > > Signed-off-by: Alexander Duyck > > > I have tested on Broadcom's Stingray cpu with 48G RAM: > __init_single_page() takes 19.30ns / 64-byte struct page > Wit the change it takes 17.33ns / 64-byte struct page I gave it a run on an OpenPower (S812LC 8348-21C) with Power8 processor and with 128G of RAM. My results for 64-byte struct page were: before: 4.6788ns after: 4.5882ns My two cents :) > Please add this data and also the data from Intel to the description. > > Thank you, > Pavel > > > --- > > arch/sparc/include/asm/pgtable_64.h | 30 ------------------------------ > > include/linux/mm.h | 34 ++++++++++++++++++++++++++++++++++ > > 2 files changed, 34 insertions(+), 30 deletions(-) > > > > diff --git a/arch/sparc/include/asm/pgtable_64.h b/arch/sparc/include/asm/pgtable_64.h > > index 1393a8ac596b..22500c3be7a9 100644 > > --- a/arch/sparc/include/asm/pgtable_64.h > > +++ b/arch/sparc/include/asm/pgtable_64.h > > @@ -231,36 +231,6 @@ > > extern struct page *mem_map_zero; > > #define ZERO_PAGE(vaddr) (mem_map_zero) > > > > -/* This macro must be updated when the size of struct page grows above 80 > > - * or reduces below 64. > > - * The idea that compiler optimizes out switch() statement, and only > > - * leaves clrx instructions > > - */ > > -#define mm_zero_struct_page(pp) do { \ > > - unsigned long *_pp = (void *)(pp); \ > > - \ > > - /* Check that struct page is either 64, 72, or 80 bytes */ \ > > - BUILD_BUG_ON(sizeof(struct page) & 7); \ > > - BUILD_BUG_ON(sizeof(struct page) < 64); \ > > - BUILD_BUG_ON(sizeof(struct page) > 80); \ > > - \ > > - switch (sizeof(struct page)) { \ > > - case 80: \ > > - _pp[9] = 0; /* fallthrough */ \ > > - case 72: \ > > - _pp[8] = 0; /* fallthrough */ \ > > - default: \ > > - _pp[7] = 0; \ > > - _pp[6] = 0; \ > > - _pp[5] = 0; \ > > - _pp[4] = 0; \ > > - _pp[3] = 0; \ > > - _pp[2] = 0; \ > > - _pp[1] = 0; \ > > - _pp[0] = 0; \ > > - } \ > > -} while (0) > > - > > /* PFNs are real physical page numbers. However, mem_map only begins to record > > * per-page information starting at pfn_base. This is to handle systems where > > * the first physical page in the machine is at some huge physical address, > > diff --git a/include/linux/mm.h b/include/linux/mm.h > > index bb0de406f8e7..ec6e57a0c14e 100644 > > --- a/include/linux/mm.h > > +++ b/include/linux/mm.h > > @@ -102,8 +102,42 @@ static inline void set_max_mapnr(unsigned long limit) { } > > * zeroing by defining this macro in . > > */ > > The comment above becomes outdated. Please change, we use optimized > mm_zero_struct_page on every 64-bit platform. > > > #ifndef mm_zero_struct_page > > +#if BITS_PER_LONG == 64 > > +/* This function must be updated when the size of struct page grows above 80 > > + * or reduces below 64. The idea that compiler optimizes out switch() > > + * statement, and only leaves move/store instructions > > + */ > > +#define mm_zero_struct_page(pp) __mm_zero_struct_page(pp) > > +static inline void __mm_zero_struct_page(struct page *page) > > +{ > > + unsigned long *_pp = (void *)page; > > + > > + /* Check that struct page is either 56, 64, 72, or 80 bytes */ > > + BUILD_BUG_ON(sizeof(struct page) & 7); > > + BUILD_BUG_ON(sizeof(struct page) < 56); > > + BUILD_BUG_ON(sizeof(struct page) > 80); > > + > > + switch (sizeof(struct page)) { > > + case 80: > > + _pp[9] = 0; /* fallthrough */ > > + case 72: > > + _pp[8] = 0; /* fallthrough */ > > + default: > > + _pp[7] = 0; /* fallthrough */ > > + case 56: > > + _pp[6] = 0; > > + _pp[5] = 0; > > + _pp[4] = 0; > > + _pp[3] = 0; > > + _pp[2] = 0; > > + _pp[1] = 0; > > + _pp[0] = 0; > > + } > > +} > > +#else > > #define mm_zero_struct_page(pp) ((void)memset((pp), 0, sizeof(struct page))) > > #endif > > +#endif > > > > /* > > * Default maximum number of active map areas, this limits the number of vmas > > > -- Sincerely yours, Mike.