1:29 a.m.
On 2023/11/30 16:21, HAGIO KAZUHITO(萩尾 一仁) wrote:
thanks for the patch.
On 2023/11/28 12:41, Huang Shijie wrote:
> If the kernel exports the vmmemap then we can use that symbol in
> crash to optimize access. vmmemap is just an array of page structs
> after all.
>
> This patch tries to get the "vmemmap" from the vmcore file.
> If we can use the "vmemmap", use the vmemmap_is_page_ptr to replace
> the generic_is_page_ptr().
I recalled that I also did a similar thing for x86_64 [1] in the past..
so it's not so slow on x86_64 and it has valid section check too.
[1]
https://github.com/crash-utility/crash/commit/4141373d9de3fea29f5d2b58f60...
I don't object to add an entry to vmcoreinfo as a way of getting the
vmemmap value. Seems like arm64 has another value from VMEMMAP_START.
but there are some concerns in crash:
- machdep->flags already has VMEMMAP flag. It's used like "if
(IS_SPARSEMEM() && (machdep->flags & VMEMMAP)" e.g. [1]. Adding the
new
flag is very confusing and inconsistent.
- Do all architectures have VMEMMAP_VADDR/END values in crash with
CONFIG_SPARSEMEM_VMEMMAP configured?
we cannot test all archs, so this kind of arch-independent change makes
me nervous. I would like to suggest an arch-specific use first. e.g.
how about making x86_64_is_page_ptr more generic and use it?
What happens if you use it on arm64? maybe the valid section can
check
it with VMEMMAP_VADDR without the vmemmap value. Just an idea though.
hmm sorry, probably this does not work, I missed this.
+ pfn = (addr - vt->vmemmap) / size;
but can VMEMMAP_VADDR and phys_offset can be used to get vmemmap value
on arm64?
Thanks,
Kazu
>
> Thanks,
> Kazu
>
>>
>> If we have vmemmap then we can implement fast page_to_pfn code in
>> vmemmap_is_page_ptr
>>
>> Test result:
>> Test the patch: "[PATCH v3] add "files -n" command for an
inode"
>> https://lists.crash-utility.osci.io/archives/list/
>> devel(a)lists.crash-utility.osci.io/thread/CRLOQP534YKEQPTCXIWVDYK4NA7BOSUK/
>>
>> Without the this patch:
>> #files -n xxx (xxx is the inode of vmlinux which is 441M)
>> This costed about 162 seconds.
>>
>> With the this patch:
>> #files -n xxx (xxx is the inode of vmlinux which is 441M)
>> This costed less then 1 second.
>>
>> Signed-off-by: Huang Shijie <shijie(a)os.amperecomputing.com>
>> ---
>> defs.h | 3 +++
>> memory.c | 35 +++++++++++++++++++++++++++++++++++
>> 2 files changed, 38 insertions(+)
>>
>> diff --git a/defs.h b/defs.h
>> index eec7b3e..25bb455 100644
>> --- a/defs.h
>> +++ b/defs.h
>> @@ -2615,6 +2615,7 @@ struct vm_table { /* kernel VM-related data
*/
>> ulong vma_cache_fills;
>> void *mem_sec;
>> char *mem_section;
>> + ulong vmemmap;
>> int ZONE_HIGHMEM;
>> ulong *node_online_map;
>> int node_online_map_len;
>> @@ -2665,10 +2666,12 @@ struct vm_table { /* kernel VM-related
data */
>> #define SLAB_OVERLOAD_PAGE (0x8000000)
>> #define SLAB_CPU_CACHE (0x10000000)
>> #define SLAB_ROOT_CACHES (0x20000000)
>> +#define SPARSEMEM_VMEMMAP (0x40000000)
>>
>> #define IS_FLATMEM() (vt->flags & FLATMEM)
>> #define IS_DISCONTIGMEM() (vt->flags & DISCONTIGMEM)
>> #define IS_SPARSEMEM() (vt->flags & SPARSEMEM)
>> +#define IS_SPARSEMEM_VMEMMAP() (vt->flags & SPARSEMEM_VMEMMAP)
>> #define IS_SPARSEMEM_EX() (vt->flags & SPARSEMEM_EX)
>>
>> #define COMMON_VADDR_SPACE() (vt->flags & COMMON_VADDR)
>> diff --git a/memory.c b/memory.c
>> index ed1a4fb..668567f 100644
>> --- a/memory.c
>> +++ b/memory.c
>> @@ -17462,6 +17462,39 @@ sparse_decode_mem_map(ulong coded_mem_map, ulong
section_nr)
>> (section_nr_to_pfn(section_nr) * SIZE(page));
>> }
>>
>> +static int
>> +vmemmap_is_page_ptr(ulong addr, physaddr_t *phys)
>> +{
>> + ulong pfn;
>> +
>> + if (IS_SPARSEMEM_VMEMMAP() &&
>> + (VMEMMAP_VADDR <= addr && addr < VMEMMAP_END)) {
>> + ulong size = SIZE(page);
>> +
>> + /* Not aligned with the page structure */
>> + if ((addr - vt->vmemmap) % size)
>> + return FALSE;
>> +
>> + pfn = (addr - vt->vmemmap) / size;
>> + if (phys)
>> + *phys = PTOB(pfn);
>> + return TRUE;
>> + }
>> + return FALSE;
>> +}
>> +
>> +static bool
>> +check_sparsemem_vmemmap(void)
>> +{
>> + if (!get_value_vmcore("SYMBOL(vmemmap)", &vt->vmemmap))
>> + return FALSE;
>> +
>> + vt->flags |= SPARSEMEM_VMEMMAP;
>> + if (machdep->is_page_ptr == generic_is_page_ptr)
>> + machdep->is_page_ptr = vmemmap_is_page_ptr;
>> + return TRUE;
>> +}
>> +
>> void
>> sparse_mem_init(void)
>> {
>> @@ -17472,6 +17505,8 @@ sparse_mem_init(void)
>> if (!IS_SPARSEMEM())
>> return;
>>
>> + check_sparsemem_vmemmap();
>> +
>> MEMBER_OFFSET_INIT(mem_section_section_mem_map, "mem_section",
>> "section_mem_map");
>>
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