From: Daniel Kiper <daniel.kiper@oracle.com>
To: xen-devel@lists.xenproject.org
Cc: jgross@suse.com, andrew.cooper3@citrix.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: [PATCH v3 02/16] x86: zero BSS using stosl instead of stosb
Date: Fri, 15 Apr 2016 14:33:02 +0200 [thread overview]
Message-ID: <1460723596-13261-3-git-send-email-daniel.kiper@oracle.com> (raw)
In-Reply-To: <1460723596-13261-1-git-send-email-daniel.kiper@oracle.com>
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);
.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 = . ;
--
1.7.10.4
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next prev parent reply other threads:[~2016-04-15 12:33 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 ` Daniel Kiper [this message]
2016-04-15 13:57 ` [PATCH v3 02/16] x86: zero BSS using stosl instead of stosb Konrad Rzeszutek Wilk
2016-04-15 15:48 ` Andrew Cooper
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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