When using 1GiB pages during early boot, use the new
memblock_virt_alloc_try_nid_raw() function to allocate memory without
zeroing it. Zeroing out hundreds or thousands of GiB in a single core
memset() call is very slow, and can make early boot last upwards of
20-30 minutes on multi TiB machines.
To be safe, still zero the first sizeof(struct boomem_huge_page) bytes
since this is used a temporary storage place for this info until
gather_bootmem_prealloc() processes them later.
The rest of the memory does not need to be zero'd as the hugetlb pages
are always zero'd on page fault.
Tested: Booted with ~3800 1G pages, and it booted successfully in
roughly the same amount of time as with 0, as opposed to the 25+
minutes it would take before.
Signed-off-by: Cannon Matthews <[email protected]>
---
mm/hugetlb.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 3612fbb32e9d..c93a2c77e881 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -2101,7 +2101,7 @@ int __alloc_bootmem_huge_page(struct hstate *h)
for_each_node_mask_to_alloc(h, nr_nodes, node, &node_states[N_MEMORY]) {
void *addr;
- addr = memblock_virt_alloc_try_nid_nopanic(
+ addr = memblock_virt_alloc_try_nid_raw(
huge_page_size(h), huge_page_size(h),
0, BOOTMEM_ALLOC_ACCESSIBLE, node);
if (addr) {
@@ -2109,7 +2109,12 @@ int __alloc_bootmem_huge_page(struct hstate *h)
* Use the beginning of the huge page to store the
* huge_bootmem_page struct (until gather_bootmem
* puts them into the mem_map).
+ *
+ * memblock_virt_alloc_try_nid_raw returns non-zero'd
+ * memory so zero out just enough for this struct, the
+ * rest will be zero'd on page fault.
*/
+ memset(addr, 0, sizeof(struct huge_bootmem_page));
m = addr;
goto found;
}
--
2.18.0.203.gfac676dfb9-goog
On 07/10/2018 11:49 AM, Cannon Matthews wrote:
> When using 1GiB pages during early boot, use the new
> memblock_virt_alloc_try_nid_raw() function to allocate memory without
> zeroing it. Zeroing out hundreds or thousands of GiB in a single core
> memset() call is very slow, and can make early boot last upwards of
> 20-30 minutes on multi TiB machines.
>
> To be safe, still zero the first sizeof(struct boomem_huge_page) bytes
> since this is used a temporary storage place for this info until
> gather_bootmem_prealloc() processes them later.
>
> The rest of the memory does not need to be zero'd as the hugetlb pages
> are always zero'd on page fault.
>
> Tested: Booted with ~3800 1G pages, and it booted successfully in
> roughly the same amount of time as with 0, as opposed to the 25+
> minutes it would take before.
>
Nice improvement!
> Signed-off-by: Cannon Matthews <[email protected]>
> ---
> mm/hugetlb.c | 7 ++++++-
> 1 file changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index 3612fbb32e9d..c93a2c77e881 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -2101,7 +2101,7 @@ int __alloc_bootmem_huge_page(struct hstate *h)
> for_each_node_mask_to_alloc(h, nr_nodes, node, &node_states[N_MEMORY]) {
> void *addr;
>
> - addr = memblock_virt_alloc_try_nid_nopanic(
> + addr = memblock_virt_alloc_try_nid_raw(
> huge_page_size(h), huge_page_size(h),
> 0, BOOTMEM_ALLOC_ACCESSIBLE, node);
> if (addr) {
> @@ -2109,7 +2109,12 @@ int __alloc_bootmem_huge_page(struct hstate *h)
> * Use the beginning of the huge page to store the
> * huge_bootmem_page struct (until gather_bootmem
> * puts them into the mem_map).
> + *
> + * memblock_virt_alloc_try_nid_raw returns non-zero'd
> + * memory so zero out just enough for this struct, the
> + * rest will be zero'd on page fault.
> */
> + memset(addr, 0, sizeof(struct huge_bootmem_page));
This forced me to look at the usage of huge_bootmem_page. It is defined as:
struct huge_bootmem_page {
struct list_head list;
struct hstate *hstate;
#ifdef CONFIG_HIGHMEM
phys_addr_t phys;
#endif
};
The list and hstate fields are set immediately after allocating the memory
block here and elsewhere. However, I can't find any code that sets phys.
Although, it is potentially used in gather_bootmem_prealloc(). It appears
powerpc used this field at one time, but no longer does.
Am I missing something?
Not an issue with this patch, rather existing code. I'd prefer not to do
the memset() "just to be safe". Unless I am missing something, I would
like to remove phys field and supporting code first. Then, this patch
without the memset.
--
Mike Kravetz
> m = addr;
> goto found;
> }
> --
> 2.18.0.203.gfac676dfb9-goog
>
On Wed 11-07-18 14:47:11, Michal Hocko wrote:
> On Tue 10-07-18 11:49:03, Cannon Matthews wrote:
> > When using 1GiB pages during early boot, use the new
> > memblock_virt_alloc_try_nid_raw() function to allocate memory without
> > zeroing it. Zeroing out hundreds or thousands of GiB in a single core
> > memset() call is very slow, and can make early boot last upwards of
> > 20-30 minutes on multi TiB machines.
> >
> > To be safe, still zero the first sizeof(struct boomem_huge_page) bytes
> > since this is used a temporary storage place for this info until
> > gather_bootmem_prealloc() processes them later.
> >
> > The rest of the memory does not need to be zero'd as the hugetlb pages
> > are always zero'd on page fault.
> >
> > Tested: Booted with ~3800 1G pages, and it booted successfully in
> > roughly the same amount of time as with 0, as opposed to the 25+
> > minutes it would take before.
>
> The patch makes perfect sense to me. I wasn't even aware that it
> zeroying memblock allocation. Thanks for spotting this and fixing it.
>
> > Signed-off-by: Cannon Matthews <[email protected]>
>
> I just do not think we need to to zero huge_bootmem_page portion of it.
> It should be sufficient to INIT_LIST_HEAD before list_add. We do
> initialize the rest explicitly already.
Forgot to mention that after that is addressed you can add
Acked-by: Michal Hocko <[email protected]>
--
Michal Hocko
SUSE Labs
On Tue 10-07-18 11:49:03, Cannon Matthews wrote:
> When using 1GiB pages during early boot, use the new
> memblock_virt_alloc_try_nid_raw() function to allocate memory without
> zeroing it. Zeroing out hundreds or thousands of GiB in a single core
> memset() call is very slow, and can make early boot last upwards of
> 20-30 minutes on multi TiB machines.
>
> To be safe, still zero the first sizeof(struct boomem_huge_page) bytes
> since this is used a temporary storage place for this info until
> gather_bootmem_prealloc() processes them later.
>
> The rest of the memory does not need to be zero'd as the hugetlb pages
> are always zero'd on page fault.
>
> Tested: Booted with ~3800 1G pages, and it booted successfully in
> roughly the same amount of time as with 0, as opposed to the 25+
> minutes it would take before.
The patch makes perfect sense to me. I wasn't even aware that it
zeroying memblock allocation. Thanks for spotting this and fixing it.
> Signed-off-by: Cannon Matthews <[email protected]>
I just do not think we need to to zero huge_bootmem_page portion of it.
It should be sufficient to INIT_LIST_HEAD before list_add. We do
initialize the rest explicitly already.
> ---
> mm/hugetlb.c | 7 ++++++-
> 1 file changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index 3612fbb32e9d..c93a2c77e881 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -2101,7 +2101,7 @@ int __alloc_bootmem_huge_page(struct hstate *h)
> for_each_node_mask_to_alloc(h, nr_nodes, node, &node_states[N_MEMORY]) {
> void *addr;
>
> - addr = memblock_virt_alloc_try_nid_nopanic(
> + addr = memblock_virt_alloc_try_nid_raw(
> huge_page_size(h), huge_page_size(h),
> 0, BOOTMEM_ALLOC_ACCESSIBLE, node);
> if (addr) {
> @@ -2109,7 +2109,12 @@ int __alloc_bootmem_huge_page(struct hstate *h)
> * Use the beginning of the huge page to store the
> * huge_bootmem_page struct (until gather_bootmem
> * puts them into the mem_map).
> + *
> + * memblock_virt_alloc_try_nid_raw returns non-zero'd
> + * memory so zero out just enough for this struct, the
> + * rest will be zero'd on page fault.
> */
> + memset(addr, 0, sizeof(struct huge_bootmem_page));
> m = addr;
> goto found;
> }
> --
> 2.18.0.203.gfac676dfb9-goog
--
Michal Hocko
SUSE Labs
On Tue 10-07-18 13:46:57, Mike Kravetz wrote:
> On 07/10/2018 11:49 AM, Cannon Matthews wrote:
> > When using 1GiB pages during early boot, use the new
> > memblock_virt_alloc_try_nid_raw() function to allocate memory without
> > zeroing it. Zeroing out hundreds or thousands of GiB in a single core
> > memset() call is very slow, and can make early boot last upwards of
> > 20-30 minutes on multi TiB machines.
> >
> > To be safe, still zero the first sizeof(struct boomem_huge_page) bytes
> > since this is used a temporary storage place for this info until
> > gather_bootmem_prealloc() processes them later.
> >
> > The rest of the memory does not need to be zero'd as the hugetlb pages
> > are always zero'd on page fault.
> >
> > Tested: Booted with ~3800 1G pages, and it booted successfully in
> > roughly the same amount of time as with 0, as opposed to the 25+
> > minutes it would take before.
> >
>
> Nice improvement!
>
> > Signed-off-by: Cannon Matthews <[email protected]>
> > ---
> > mm/hugetlb.c | 7 ++++++-
> > 1 file changed, 6 insertions(+), 1 deletion(-)
> >
> > diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> > index 3612fbb32e9d..c93a2c77e881 100644
> > --- a/mm/hugetlb.c
> > +++ b/mm/hugetlb.c
> > @@ -2101,7 +2101,7 @@ int __alloc_bootmem_huge_page(struct hstate *h)
> > for_each_node_mask_to_alloc(h, nr_nodes, node, &node_states[N_MEMORY]) {
> > void *addr;
> >
> > - addr = memblock_virt_alloc_try_nid_nopanic(
> > + addr = memblock_virt_alloc_try_nid_raw(
> > huge_page_size(h), huge_page_size(h),
> > 0, BOOTMEM_ALLOC_ACCESSIBLE, node);
> > if (addr) {
> > @@ -2109,7 +2109,12 @@ int __alloc_bootmem_huge_page(struct hstate *h)
> > * Use the beginning of the huge page to store the
> > * huge_bootmem_page struct (until gather_bootmem
> > * puts them into the mem_map).
> > + *
> > + * memblock_virt_alloc_try_nid_raw returns non-zero'd
> > + * memory so zero out just enough for this struct, the
> > + * rest will be zero'd on page fault.
> > */
> > + memset(addr, 0, sizeof(struct huge_bootmem_page));
>
> This forced me to look at the usage of huge_bootmem_page. It is defined as:
> struct huge_bootmem_page {
> struct list_head list;
> struct hstate *hstate;
> #ifdef CONFIG_HIGHMEM
> phys_addr_t phys;
> #endif
> };
>
> The list and hstate fields are set immediately after allocating the memory
> block here and elsewhere. However, I can't find any code that sets phys.
> Although, it is potentially used in gather_bootmem_prealloc(). It appears
> powerpc used this field at one time, but no longer does.
>
> Am I missing something?
If yes, then I am missing it as well. phys is a cool name to grep for...
Anyway, does it really make any sense to allow gigantic pages on HIGHMEM
systems in the first place?
--
Michal Hocko
SUSE Labs
On 07/11/2018 05:48 AM, Michal Hocko wrote:
> On Wed 11-07-18 14:47:11, Michal Hocko wrote:
>> On Tue 10-07-18 11:49:03, Cannon Matthews wrote:
>>> When using 1GiB pages during early boot, use the new
>>> memblock_virt_alloc_try_nid_raw() function to allocate memory without
>>> zeroing it. Zeroing out hundreds or thousands of GiB in a single core
>>> memset() call is very slow, and can make early boot last upwards of
>>> 20-30 minutes on multi TiB machines.
>>>
>>> To be safe, still zero the first sizeof(struct boomem_huge_page) bytes
>>> since this is used a temporary storage place for this info until
>>> gather_bootmem_prealloc() processes them later.
>>>
>>> The rest of the memory does not need to be zero'd as the hugetlb pages
>>> are always zero'd on page fault.
>>>
>>> Tested: Booted with ~3800 1G pages, and it booted successfully in
>>> roughly the same amount of time as with 0, as opposed to the 25+
>>> minutes it would take before.
>>
>> The patch makes perfect sense to me. I wasn't even aware that it
>> zeroying memblock allocation. Thanks for spotting this and fixing it.
>>
>>> Signed-off-by: Cannon Matthews <[email protected]>
>>
>> I just do not think we need to to zero huge_bootmem_page portion of it.
>> It should be sufficient to INIT_LIST_HEAD before list_add. We do
>> initialize the rest explicitly already.
>
> Forgot to mention that after that is addressed you can add
> Acked-by: Michal Hocko <[email protected]>
Cannon,
How about if you make this change suggested by Michal, and I will submit
a separate patch to revert the patch which added the phys field to
huge_bootmem_page structure.
FWIW,
Reviewed-by: Mike Kravetz <[email protected]>
--
Mike Kravetz