* [PATCH] x86/mm: trivial code cleanup for memory_map_top_doown()
@ 2017-02-17 14:30 Wei Yang
2017-03-13 18:50 ` Borislav Petkov
0 siblings, 1 reply; 6+ messages in thread
From: Wei Yang @ 2017-02-17 14:30 UTC (permalink / raw)
To: tglx, mingo, hpa; +Cc: x86, linux-kernel, Wei Yang
In case (last_start <= step_size), start is for sure to be 0. So, it is
save to do the round_down for all cases and set start to map_start when
start is smaller than map_start.
>From the performance point of view, this also reduces the check on each
iteration.
This patch unifies the code on round_down memory range in
memory_map_top_doown() and also removes a redundant assignment of start
which will be assigned the correct value in each iteration.
Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
---
arch/x86/mm/init.c | 10 ++++------
1 file changed, 4 insertions(+), 6 deletions(-)
diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c
index 22af912d66d2..d8ad5e825b10 100644
--- a/arch/x86/mm/init.c
+++ b/arch/x86/mm/init.c
@@ -514,7 +514,7 @@ static void __init memory_map_top_down(unsigned long map_start,
step_size = PMD_SIZE;
max_pfn_mapped = 0; /* will get exact value next */
min_pfn_mapped = real_end >> PAGE_SHIFT;
- last_start = start = real_end;
+ last_start = real_end;
/*
* We start from the top (end of memory) and go to the bottom.
@@ -523,12 +523,10 @@ static void __init memory_map_top_down(unsigned long map_start,
* for page table.
*/
while (last_start > map_start) {
- if (last_start > step_size) {
- start = round_down(last_start - 1, step_size);
- if (start < map_start)
- start = map_start;
- } else
+ start = round_down(last_start - 1, step_size);
+ if (start < map_start)
start = map_start;
+
mapped_ram_size += init_range_memory_mapping(start,
last_start);
last_start = start;
--
2.11.0
^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH] x86/mm: trivial code cleanup for memory_map_top_doown()
2017-02-17 14:30 [PATCH] x86/mm: trivial code cleanup for memory_map_top_doown() Wei Yang
@ 2017-03-13 18:50 ` Borislav Petkov
2017-03-14 3:56 ` Wei Yang
0 siblings, 1 reply; 6+ messages in thread
From: Borislav Petkov @ 2017-03-13 18:50 UTC (permalink / raw)
To: Wei Yang; +Cc: tglx, mingo, hpa, x86, linux-kernel
On Fri, Feb 17, 2017 at 10:30:33PM +0800, Wei Yang wrote:
> In case (last_start <= step_size), start is for sure to be 0. So, it is
Well, lemme see:
[ 0.000000] memory_map_top_down: entry, [0x100000:0x7ffdf000)
[ 0.000000] memory_map_top_down: addr: 0x7fc00000, real_end: 0x7fe00000
[ 0.000000] memory_map_top_down: last_start: 0x40000000 <= step_size: 0x2000000000, start: 0x40000000
^^^^^^^^^^
It doesn't look like 0 to me.
---
diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c
index 2193799ca800..d3b02a416df3 100644
--- a/arch/x86/mm/init.c
+++ b/arch/x86/mm/init.c
@@ -506,10 +506,14 @@ static void __init memory_map_top_down(unsigned long map_start,
unsigned long addr;
unsigned long mapped_ram_size = 0;
+ pr_info("%s: entry, [0x%lx:0x%lx)\n", __func__, map_start, map_end);
+
/* xen has big range in reserved near end of ram, skip it at first.*/
addr = memblock_find_in_range(map_start, map_end, PMD_SIZE, PMD_SIZE);
real_end = addr + PMD_SIZE;
+ pr_info("%s: addr: 0x%lx, real_end: 0x%lx\n", __func__, addr, real_end);
+
/* step_size need to be small so pgt_buf from BRK could cover it */
step_size = PMD_SIZE;
max_pfn_mapped = 0; /* will get exact value next */
@@ -527,8 +531,13 @@ static void __init memory_map_top_down(unsigned long map_start,
start = round_down(last_start - 1, step_size);
if (start < map_start)
start = map_start;
- } else
+ } else {
+ pr_info("%s: last_start: 0x%lx <= step_size: 0x%lx, start: 0x%lx\n",
+ __func__, last_start, step_size, start);
+
start = map_start;
+ }
+
mapped_ram_size += init_range_memory_mapping(start,
last_start);
last_start = start;
--
Regards/Gruss,
Boris.
Good mailing practices for 400: avoid top-posting and trim the reply.
^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH] x86/mm: trivial code cleanup for memory_map_top_doown()
2017-03-13 18:50 ` Borislav Petkov
@ 2017-03-14 3:56 ` Wei Yang
2017-03-20 2:26 ` Wei Yang
2017-05-02 13:26 ` Wei Yang
0 siblings, 2 replies; 6+ messages in thread
From: Wei Yang @ 2017-03-14 3:56 UTC (permalink / raw)
To: Borislav Petkov; +Cc: Wei Yang, tglx, mingo, hpa, x86, linux-kernel
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On Mon, Mar 13, 2017 at 07:50:21PM +0100, Borislav Petkov wrote:
>On Fri, Feb 17, 2017 at 10:30:33PM +0800, Wei Yang wrote:
>> In case (last_start <= step_size), start is for sure to be 0. So, it is
>
Hmm, I may write it more specific:
"start" is for sure to be set to 0 with round_down(last_start - 1, step_size).
>Well, lemme see:
>
>[ 0.000000] memory_map_top_down: entry, [0x100000:0x7ffdf000)
>[ 0.000000] memory_map_top_down: addr: 0x7fc00000, real_end: 0x7fe00000
>[ 0.000000] memory_map_top_down: last_start: 0x40000000 <= step_size: 0x2000000000, start: 0x40000000
> ^^^^^^^^^^
>It doesn't look like 0 to me.
>
>---
>diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c
>index 2193799ca800..d3b02a416df3 100644
>--- a/arch/x86/mm/init.c
>+++ b/arch/x86/mm/init.c
>@@ -527,8 +531,13 @@ static void __init memory_map_top_down(unsigned long map_start,
> start = round_down(last_start - 1, step_size);
> if (start < map_start)
> start = map_start;
>- } else
>+ } else {
>+ pr_info("%s: last_start: 0x%lx <= step_size: 0x%lx, start: 0x%lx\n",
>+ __func__, last_start, step_size, start);
>+
If you change this log with the following
pr_err("%s: last_start: 0x%lx <= step_size: 0x%lx, start: 0x%lx\n",
__func__, last_start, step_size,
round_down(last_start - 1, step_size));
You could see after calculation, start is 0 when (last_start <= step_size).
--
Wei Yang
Help you, Help me
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^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] x86/mm: trivial code cleanup for memory_map_top_doown()
2017-03-14 3:56 ` Wei Yang
@ 2017-03-20 2:26 ` Wei Yang
2017-05-02 13:26 ` Wei Yang
1 sibling, 0 replies; 6+ messages in thread
From: Wei Yang @ 2017-03-20 2:26 UTC (permalink / raw)
To: Wei Yang; +Cc: Borislav Petkov, tglx, mingo, hpa, x86, linux-kernel
[-- Attachment #1: Type: text/plain, Size: 1695 bytes --]
Hi, Borislav
Do you still have some concern on this change?
On Tue, Mar 14, 2017 at 11:56:39AM +0800, Wei Yang wrote:
>On Mon, Mar 13, 2017 at 07:50:21PM +0100, Borislav Petkov wrote:
>>On Fri, Feb 17, 2017 at 10:30:33PM +0800, Wei Yang wrote:
>>> In case (last_start <= step_size), start is for sure to be 0. So, it is
>>
>
>Hmm, I may write it more specific:
>
>"start" is for sure to be set to 0 with round_down(last_start - 1, step_size).
>
>>Well, lemme see:
>>
>>[ 0.000000] memory_map_top_down: entry, [0x100000:0x7ffdf000)
>>[ 0.000000] memory_map_top_down: addr: 0x7fc00000, real_end: 0x7fe00000
>>[ 0.000000] memory_map_top_down: last_start: 0x40000000 <= step_size: 0x2000000000, start: 0x40000000
>> ^^^^^^^^^^
>>It doesn't look like 0 to me.
>>
>>---
>>diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c
>>index 2193799ca800..d3b02a416df3 100644
>>--- a/arch/x86/mm/init.c
>>+++ b/arch/x86/mm/init.c
>>@@ -527,8 +531,13 @@ static void __init memory_map_top_down(unsigned long map_start,
>> start = round_down(last_start - 1, step_size);
>> if (start < map_start)
>> start = map_start;
>>- } else
>>+ } else {
>>+ pr_info("%s: last_start: 0x%lx <= step_size: 0x%lx, start: 0x%lx\n",
>>+ __func__, last_start, step_size, start);
>>+
>
>If you change this log with the following
>
> pr_err("%s: last_start: 0x%lx <= step_size: 0x%lx, start: 0x%lx\n",
> __func__, last_start, step_size,
> round_down(last_start - 1, step_size));
>
>You could see after calculation, start is 0 when (last_start <= step_size).
>
>--
>Wei Yang
>Help you, Help me
--
Wei Yang
Help you, Help me
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^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] x86/mm: trivial code cleanup for memory_map_top_doown()
2017-03-14 3:56 ` Wei Yang
2017-03-20 2:26 ` Wei Yang
@ 2017-05-02 13:26 ` Wei Yang
2017-08-03 7:12 ` Wei Yang
1 sibling, 1 reply; 6+ messages in thread
From: Wei Yang @ 2017-05-02 13:26 UTC (permalink / raw)
To: Wei Yang; +Cc: Borislav Petkov, tglx, mingo, hpa, x86, linux-kernel
[-- Attachment #1: Type: text/plain, Size: 1714 bytes --]
Hi, Borislav and all
Do you agree with my analysis or you have other comments?
On Tue, Mar 14, 2017 at 11:56:39AM +0800, Wei Yang wrote:
>On Mon, Mar 13, 2017 at 07:50:21PM +0100, Borislav Petkov wrote:
>>On Fri, Feb 17, 2017 at 10:30:33PM +0800, Wei Yang wrote:
>>> In case (last_start <= step_size), start is for sure to be 0. So, it is
>>
>
>Hmm, I may write it more specific:
>
>"start" is for sure to be set to 0 with round_down(last_start - 1, step_size).
>
>>Well, lemme see:
>>
>>[ 0.000000] memory_map_top_down: entry, [0x100000:0x7ffdf000)
>>[ 0.000000] memory_map_top_down: addr: 0x7fc00000, real_end: 0x7fe00000
>>[ 0.000000] memory_map_top_down: last_start: 0x40000000 <= step_size: 0x2000000000, start: 0x40000000
>> ^^^^^^^^^^
>>It doesn't look like 0 to me.
>>
>>---
>>diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c
>>index 2193799ca800..d3b02a416df3 100644
>>--- a/arch/x86/mm/init.c
>>+++ b/arch/x86/mm/init.c
>>@@ -527,8 +531,13 @@ static void __init memory_map_top_down(unsigned long map_start,
>> start = round_down(last_start - 1, step_size);
>> if (start < map_start)
>> start = map_start;
>>- } else
>>+ } else {
>>+ pr_info("%s: last_start: 0x%lx <= step_size: 0x%lx, start: 0x%lx\n",
>>+ __func__, last_start, step_size, start);
>>+
>
>If you change this log with the following
>
> pr_err("%s: last_start: 0x%lx <= step_size: 0x%lx, start: 0x%lx\n",
> __func__, last_start, step_size,
> round_down(last_start - 1, step_size));
>
>You could see after calculation, start is 0 when (last_start <= step_size).
>
>--
>Wei Yang
>Help you, Help me
--
Wei Yang
Help you, Help me
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^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] x86/mm: trivial code cleanup for memory_map_top_doown()
2017-05-02 13:26 ` Wei Yang
@ 2017-08-03 7:12 ` Wei Yang
0 siblings, 0 replies; 6+ messages in thread
From: Wei Yang @ 2017-08-03 7:12 UTC (permalink / raw)
To: Wei Yang
Cc: Borislav Petkov, Thomas Gleixner, Ingo Molnar, H. Peter Anvin,
the arch/x86 maintainers, Linux Kernel Mailing List
Hmm.... ping...
On Tue, May 2, 2017 at 9:26 PM, Wei Yang <richard.weiyang@gmail.com> wrote:
> Hi, Borislav and all
>
> Do you agree with my analysis or you have other comments?
>
> On Tue, Mar 14, 2017 at 11:56:39AM +0800, Wei Yang wrote:
>>On Mon, Mar 13, 2017 at 07:50:21PM +0100, Borislav Petkov wrote:
>>>On Fri, Feb 17, 2017 at 10:30:33PM +0800, Wei Yang wrote:
>>>> In case (last_start <= step_size), start is for sure to be 0. So, it is
>>>
>>
>>Hmm, I may write it more specific:
>>
>>"start" is for sure to be set to 0 with round_down(last_start - 1, step_size).
>>
>>>Well, lemme see:
>>>
>>>[ 0.000000] memory_map_top_down: entry, [0x100000:0x7ffdf000)
>>>[ 0.000000] memory_map_top_down: addr: 0x7fc00000, real_end: 0x7fe00000
>>>[ 0.000000] memory_map_top_down: last_start: 0x40000000 <= step_size: 0x2000000000, start: 0x40000000
>>> ^^^^^^^^^^
>>>It doesn't look like 0 to me.
>>>
>>>---
>>>diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c
>>>index 2193799ca800..d3b02a416df3 100644
>>>--- a/arch/x86/mm/init.c
>>>+++ b/arch/x86/mm/init.c
>>>@@ -527,8 +531,13 @@ static void __init memory_map_top_down(unsigned long map_start,
>>> start = round_down(last_start - 1, step_size);
>>> if (start < map_start)
>>> start = map_start;
>>>- } else
>>>+ } else {
>>>+ pr_info("%s: last_start: 0x%lx <= step_size: 0x%lx, start: 0x%lx\n",
>>>+ __func__, last_start, step_size, start);
>>>+
>>
>>If you change this log with the following
>>
>> pr_err("%s: last_start: 0x%lx <= step_size: 0x%lx, start: 0x%lx\n",
>> __func__, last_start, step_size,
>> round_down(last_start - 1, step_size));
>>
>>You could see after calculation, start is 0 when (last_start <= step_size).
>>
>>--
>>Wei Yang
>>Help you, Help me
>
>
>
> --
> Wei Yang
> Help you, Help me
^ permalink raw reply [flat|nested] 6+ messages in thread
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2017-02-17 14:30 [PATCH] x86/mm: trivial code cleanup for memory_map_top_doown() Wei Yang
2017-03-13 18:50 ` Borislav Petkov
2017-03-14 3:56 ` Wei Yang
2017-03-20 2:26 ` Wei Yang
2017-05-02 13:26 ` Wei Yang
2017-08-03 7:12 ` Wei Yang
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