From: Andrew Cooper <andrew.cooper3@citrix.com>
To: Daniel Kiper <daniel.kiper@oracle.com>, xen-devel@lists.xenproject.org
Cc: jgross@suse.com, stefano.stabellini@eu.citrix.com,
cardoe@cardoe.com, pgnet.dev@gmail.com, ning.sun@intel.com,
david.vrabel@citrix.com, jbeulich@suse.com,
qiaowei.ren@intel.com, richard.l.maliszewski@intel.com,
gang.wei@intel.com, fu.wei@linaro.org
Subject: Re: [PATCH v3 02/16] x86: zero BSS using stosl instead of stosb
Date: Fri, 15 Apr 2016 16:48:59 +0100 [thread overview]
Message-ID: <57110D6B.8000407@citrix.com> (raw)
In-Reply-To: <1460723596-13261-3-git-send-email-daniel.kiper@oracle.com>
On 15/04/16 13:33, Daniel Kiper wrote:
> Speedup BSS initialization by using stosl instead of stosb.
>
> Some may argue that Intel Ivy Bridge and later provide ERMSB feature.
> This means that "rep stosb" gives better throughput than "rep stosl" on
> above mentioned CPUs. However, this feature is only available on newer
> Intel processors and e.g. AMD does not provide it at all. So, stosb will
> just give real benefits and even beat stosl only on limited number of
> machines. On the other hand stosl will speedup BSS initialization on
> all x86 platforms. Hence, use stosl instead of stosb.
>
> Additionally, align relevant comment to coding style.
>
> Suggested-by: Andrew Cooper <andrew.cooper3@citrix.com>
> Signed-off-by: Daniel Kiper <daniel.kiper@oracle.com>
> ---
> v3 - suggestions/fixes:
> - improve comments
> (suggested by Konrad Rzeszutek Wilk),
> - improve commit message
> (suggested by Jan Beulich).
> ---
> xen/arch/x86/boot/head.S | 5 +++--
> xen/arch/x86/xen.lds.S | 3 +++
> 2 files changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/xen/arch/x86/boot/head.S b/xen/arch/x86/boot/head.S
> index f3501fd..32a54a0 100644
> --- a/xen/arch/x86/boot/head.S
> +++ b/xen/arch/x86/boot/head.S
> @@ -123,12 +123,13 @@ __start:
> call reloc
> mov %eax,sym_phys(multiboot_ptr)
>
> - /* Initialize BSS (no nasty surprises!) */
> + /* Initialize BSS (no nasty surprises!). */
> mov $sym_phys(__bss_start),%edi
> mov $sym_phys(__bss_end),%ecx
> sub %edi,%ecx
> + shr $2,%ecx
> xor %eax,%eax
> - rep stosb
> + rep stosl
>
> /* Interrogate CPU extended features via CPUID. */
> mov $0x80000000,%eax
> diff --git a/xen/arch/x86/xen.lds.S b/xen/arch/x86/xen.lds.S
> index 961f48f..6802da1 100644
> --- a/xen/arch/x86/xen.lds.S
> +++ b/xen/arch/x86/xen.lds.S
> @@ -191,6 +191,8 @@ SECTIONS
> CONSTRUCTORS
> } :text
>
> + /* Align BSS to speedup its initialization. */
> + . = ALIGN(4);
This is not needed. There is already appropriate alignment before
__bss_start.
Also, you need to rebase this series onto staging - there are a lot of
changes you are missing.
~Andrew
> .bss : { /* BSS */
> . = ALIGN(STACK_SIZE);
> __bss_start = .;
> @@ -205,6 +207,7 @@ SECTIONS
> *(.bss.percpu.read_mostly)
> . = ALIGN(SMP_CACHE_BYTES);
> __per_cpu_data_end = .;
> + . = ALIGN(4);
> __bss_end = .;
> } :text
> _end = . ;
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next prev parent reply other threads:[~2016-04-15 15:49 UTC|newest]
Thread overview: 94+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-04-15 12:33 [PATCH v3 00/16] x86: multiboot2 protocol support Daniel Kiper
2016-04-15 12:33 ` [PATCH v3 01/16] x86/boot: do not create unwind tables Daniel Kiper
2016-04-15 15:45 ` Andrew Cooper
2016-04-15 12:33 ` [PATCH v3 02/16] x86: zero BSS using stosl instead of stosb Daniel Kiper
2016-04-15 13:57 ` Konrad Rzeszutek Wilk
2016-04-15 15:48 ` Andrew Cooper [this message]
2016-04-15 12:33 ` [PATCH v3 03/16] x86/boot: call reloc() using cdecl calling convention Daniel Kiper
2016-04-15 15:56 ` Andrew Cooper
2016-06-17 8:41 ` Daniel Kiper
2016-06-17 9:30 ` Jan Beulich
2016-05-24 8:42 ` Jan Beulich
2016-04-15 12:33 ` [PATCH v3 04/16] x86/boot/reloc: create generic alloc and copy functions Daniel Kiper
2016-04-15 12:33 ` [PATCH v3 05/16] x86/boot: use %ecx instead of %eax Daniel Kiper
2016-04-15 12:33 ` [PATCH v3 06/16] x86/boot/reloc: Rename some variables and rearrange code a bit Daniel Kiper
2016-04-15 12:33 ` [PATCH v3 07/16] x86/boot: create *.lnk files with linker script Daniel Kiper
2016-04-15 14:04 ` Konrad Rzeszutek Wilk
2016-05-24 9:05 ` Jan Beulich
2016-05-24 12:28 ` Daniel Kiper
2016-05-24 12:52 ` Jan Beulich
2016-06-17 9:06 ` Daniel Kiper
2016-06-17 10:04 ` Jan Beulich
2016-06-17 10:34 ` Daniel Kiper
2016-04-15 12:33 ` [PATCH v3 08/16] x86: add multiboot2 protocol support Daniel Kiper
2016-05-24 15:46 ` Jan Beulich
2016-05-25 16:34 ` Daniel Kiper
2016-05-26 10:28 ` Andrew Cooper
2016-05-27 8:08 ` Jan Beulich
2016-05-27 8:13 ` Andrew Cooper
2016-05-27 8:24 ` Jan Beulich
2016-05-27 8:11 ` Jan Beulich
2016-04-15 12:33 ` [PATCH v3 09/16] efi: explicitly define efi struct in xen/arch/x86/efi/stub.c Daniel Kiper
2016-05-25 7:03 ` Jan Beulich
2016-05-25 16:45 ` Daniel Kiper
2016-05-27 8:16 ` Jan Beulich
2016-06-01 15:07 ` Daniel Kiper
2016-07-05 18:33 ` Daniel Kiper
2016-07-06 6:55 ` Jan Beulich
2016-07-06 10:27 ` Daniel Kiper
2016-07-06 12:00 ` Jan Beulich
2016-07-06 12:55 ` Daniel Kiper
2016-04-15 12:33 ` [PATCH v3 10/16] efi: create efi_enabled() Daniel Kiper
2016-05-25 7:20 ` Jan Beulich
2016-05-25 17:15 ` Daniel Kiper
2016-05-26 10:31 ` Andrew Cooper
2016-05-27 8:22 ` Jan Beulich
2016-06-01 15:23 ` Daniel Kiper
2016-06-01 15:41 ` Jan Beulich
2016-06-01 19:28 ` Daniel Kiper
2016-06-02 8:06 ` Jan Beulich
2016-04-15 12:33 ` [PATCH v3 11/16] efi: build xen.gz with EFI code Daniel Kiper
2016-05-25 7:53 ` Jan Beulich
2016-05-25 19:07 ` Daniel Kiper
2016-05-27 8:31 ` Jan Beulich
2016-06-01 15:48 ` Daniel Kiper
2016-06-01 15:58 ` Jan Beulich
2016-06-01 19:39 ` Daniel Kiper
2016-04-15 12:33 ` [PATCH v3 12/16 - RFC] x86/efi: create new early memory allocator Daniel Kiper
2016-05-25 8:39 ` Jan Beulich
2016-05-25 19:48 ` Daniel Kiper
2016-05-27 8:37 ` Jan Beulich
2016-06-01 15:58 ` Daniel Kiper
2016-06-01 16:02 ` Jan Beulich
2016-06-01 19:53 ` Daniel Kiper
2016-06-02 8:11 ` Jan Beulich
2016-06-02 10:43 ` Daniel Kiper
2016-06-02 11:10 ` Jan Beulich
2016-06-01 16:01 ` Daniel Kiper
2016-07-05 18:26 ` Daniel Kiper
2016-07-06 7:22 ` Jan Beulich
2016-07-06 11:15 ` Daniel Kiper
2016-04-15 12:33 ` [PATCH v3 13/16 - RFC] x86: add multiboot2 protocol support for EFI platforms Daniel Kiper
2016-05-25 9:32 ` Jan Beulich
2016-05-25 10:29 ` Jan Beulich
2016-05-25 21:02 ` Daniel Kiper
2016-05-27 9:02 ` Jan Beulich
2016-06-01 19:03 ` Daniel Kiper
2016-06-02 8:34 ` Jan Beulich
2016-06-02 16:12 ` Daniel Kiper
2016-06-03 9:26 ` Jan Beulich
2016-06-03 17:06 ` Konrad Rzeszutek Wilk
2016-04-15 12:33 ` [PATCH v3 14/16] x86/boot: implement early command line parser in C Daniel Kiper
2016-05-25 10:33 ` Jan Beulich
2016-05-25 21:36 ` Daniel Kiper
2016-05-27 9:33 ` Jan Beulich
2016-06-02 8:15 ` Daniel Kiper
2016-06-02 8:39 ` Jan Beulich
2016-04-15 12:33 ` [PATCH v3 15/16 - RFC] x86: make Xen early boot code relocatable Daniel Kiper
2016-05-25 10:48 ` Jan Beulich
2016-04-15 12:33 ` [PATCH v3 16/16] x86: add multiboot2 protocol support for relocatable images Daniel Kiper
2016-05-25 11:03 ` Jan Beulich
2016-06-01 13:35 ` Daniel Kiper
2016-06-01 14:44 ` Jan Beulich
2016-06-01 19:16 ` Daniel Kiper
2016-06-02 8:41 ` Jan Beulich
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