From: Pavel Tatashin <pasha.tatashin@gmail.com>
To: Alexander Duyck <alexander.h.duyck@linux.intel.com>,
linux-mm@kvack.org, akpm@linux-foundation.org
Cc: 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
Subject: Re: [mm PATCH v3 1/6] mm: Use mm_zero_struct_page from SPARC on all 64b architectures
Date: Tue, 16 Oct 2018 15:01:11 -0400 [thread overview]
Message-ID: <57c559f6-4858-7a52-7fbb-979caa08f240@gmail.com> (raw)
In-Reply-To: <20181015202656.2171.92963.stgit@localhost.localdomain>
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 <alexander.h.duyck@linux.intel.com>
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
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 <asm/pgtable.h>.
> */
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
>
next prev parent reply other threads:[~2018-10-16 19:01 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-10-15 20:26 [mm PATCH v3 0/6] Deferred page init improvements Alexander Duyck
2018-10-15 20:26 ` [mm PATCH v3 1/6] mm: Use mm_zero_struct_page from SPARC on all 64b architectures Alexander Duyck
2018-10-16 19:01 ` Pavel Tatashin [this message]
2018-10-17 7:30 ` Mike Rapoport
2018-10-17 14:52 ` Alexander Duyck
2018-10-17 8:47 ` Michal Hocko
2018-10-17 15:07 ` Alexander Duyck
2018-10-17 15:12 ` Pavel Tatashin
2018-10-17 15:40 ` David Laight
2018-10-17 16:31 ` Alexander Duyck
2018-10-17 17:08 ` Pavel Tatashin
2018-10-17 16:34 ` Michal Hocko
2018-10-15 20:27 ` [mm PATCH v3 2/6] mm: Drop meminit_pfn_in_nid as it is redundant Alexander Duyck
2018-10-16 20:33 ` Pavel Tatashin
2018-10-16 20:49 ` Alexander Duyck
2018-10-16 21:06 ` Pavel Tatashin
2018-10-17 9:04 ` Michal Hocko
2018-10-15 20:27 ` [mm PATCH v3 3/6] mm: Use memblock/zone specific iterator for handling deferred page init Alexander Duyck
2018-10-17 9:11 ` Michal Hocko
2018-10-17 15:17 ` Alexander Duyck
2018-10-17 16:42 ` Mike Rapoport
2018-10-15 20:27 ` [mm PATCH v3 4/6] mm: Move hot-plug specific memory init into separate functions and optimize Alexander Duyck
2018-10-17 9:18 ` Michal Hocko
2018-10-17 15:26 ` Alexander Duyck
2018-10-24 12:36 ` Michal Hocko
2018-10-24 15:08 ` Alexander Duyck
2018-10-24 15:27 ` Michal Hocko
2018-10-24 17:35 ` Alexander Duyck
2018-10-25 12:41 ` Michal Hocko
2018-10-15 20:27 ` [mm PATCH v3 5/6] mm: Use common iterator for deferred_init_pages and deferred_free_pages Alexander Duyck
2018-10-15 20:27 ` [mm PATCH v3 6/6] mm: Add reserved flag setting to set_page_links Alexander Duyck
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=57c559f6-4858-7a52-7fbb-979caa08f240@gmail.com \
--to=pasha.tatashin@gmail.com \
--cc=akpm@linux-foundation.org \
--cc=alexander.h.duyck@linux.intel.com \
--cc=dan.j.williams@intel.com \
--cc=dave.jiang@intel.com \
--cc=davem@davemloft.net \
--cc=khalid.aziz@oracle.com \
--cc=kirill.shutemov@linux.intel.com \
--cc=ldufour@linux.vnet.ibm.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=mgorman@techsingularity.net \
--cc=mhocko@suse.com \
--cc=mingo@kernel.org \
--cc=pavel.tatashin@microsoft.com \
--cc=rppt@linux.vnet.ibm.com \
--cc=sparclinux@vger.kernel.org \
--cc=vbabka@suse.cz \
--cc=willy@infradead.org \
--cc=yi.z.zhang@linux.intel.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).