| Message ID | 20210415084005.25049-9-songmuchun@bytedance.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Free some vmemmap pages of HugeTLB page | expand |
On Thu, Apr 15, 2021 at 04:40:04PM +0800, Muchun Song wrote: > bool mhp_supports_memmap_on_memory(unsigned long size) > { > + bool supported; > unsigned long nr_vmemmap_pages = size / PAGE_SIZE; > unsigned long vmemmap_size = nr_vmemmap_pages * sizeof(struct page); > unsigned long remaining_size = size - vmemmap_size; > @@ -1011,11 +1012,18 @@ bool mhp_supports_memmap_on_memory(unsigned long size) > * altmap as an alternative source of memory, and we do not exactly > * populate a single PMD. > */ > - return memmap_on_memory && > - IS_ENABLED(CONFIG_MHP_MEMMAP_ON_MEMORY) && > - size == memory_block_size_bytes() && > - IS_ALIGNED(vmemmap_size, PMD_SIZE) && > - IS_ALIGNED(remaining_size, pageblock_nr_pages << PAGE_SHIFT); > + supported = memmap_on_memory && > + IS_ENABLED(CONFIG_MHP_MEMMAP_ON_MEMORY) && > + size == memory_block_size_bytes() && > + IS_ALIGNED(vmemmap_size, PMD_SIZE) && > + IS_ALIGNED(remaining_size, pageblock_nr_pages << PAGE_SHIFT); > + > + if (supported && is_hugetlb_free_vmemmap_enabled()) { > + pr_info("Cannot enable memory_hotplug.memmap_on_memory, it is not compatible with hugetlb_free_vmemmap\n"); > + supported = false; > + } I would not print anything and rather have return memmap_on_memory && !is_hugetlb_free_vmemmap_enabled && IS_ENABLED(CONFIG_MHP_MEMMAP_ON_MEMORY) && size == memory_block_size_bytes() && IS_ALIGNED(vmemmap_size, PMD_SIZE) && IS_ALIGNED(remaining_size, pageblock_nr_pages << PAGE_SHIFT); Documentation/admin-guide/kernel-parameters.txt already provides an explanation on memory_hotplug.memmap_on_memory parameter that states that the feature cannot be enabled when using hugetlb-vmemmap optimization. Users can always check whether the feature is enabled via /sys/modules/memory_hotplug/parameters/memmap_on_memory. Also, I did not check if it is, but if not, the fact about hugetlb-vmemmmap vs hotplug-vmemmap should also be called out in the hugetlb-vmemmap kernel parameter. Thanks
On Tue, Apr 20, 2021 at 6:35 PM Oscar Salvador <osalvador@suse.de> wrote: > > On Thu, Apr 15, 2021 at 04:40:04PM +0800, Muchun Song wrote: > > bool mhp_supports_memmap_on_memory(unsigned long size) > > { > > + bool supported; > > unsigned long nr_vmemmap_pages = size / PAGE_SIZE; > > unsigned long vmemmap_size = nr_vmemmap_pages * sizeof(struct page); > > unsigned long remaining_size = size - vmemmap_size; > > @@ -1011,11 +1012,18 @@ bool mhp_supports_memmap_on_memory(unsigned long size) > > * altmap as an alternative source of memory, and we do not exactly > > * populate a single PMD. > > */ > > - return memmap_on_memory && > > - IS_ENABLED(CONFIG_MHP_MEMMAP_ON_MEMORY) && > > - size == memory_block_size_bytes() && > > - IS_ALIGNED(vmemmap_size, PMD_SIZE) && > > - IS_ALIGNED(remaining_size, pageblock_nr_pages << PAGE_SHIFT); > > + supported = memmap_on_memory && > > + IS_ENABLED(CONFIG_MHP_MEMMAP_ON_MEMORY) && > > + size == memory_block_size_bytes() && > > + IS_ALIGNED(vmemmap_size, PMD_SIZE) && > > + IS_ALIGNED(remaining_size, pageblock_nr_pages << PAGE_SHIFT); > > + > > + if (supported && is_hugetlb_free_vmemmap_enabled()) { > > + pr_info("Cannot enable memory_hotplug.memmap_on_memory, it is not compatible with hugetlb_free_vmemmap\n"); > > + supported = false; > > + } > > I would not print anything and rather have > > return memmap_on_memory && > !is_hugetlb_free_vmemmap_enabled && > IS_ENABLED(CONFIG_MHP_MEMMAP_ON_MEMORY) && > size == memory_block_size_bytes() && > IS_ALIGNED(vmemmap_size, PMD_SIZE) && > IS_ALIGNED(remaining_size, pageblock_nr_pages << PAGE_SHIFT); OK. Will do. > > Documentation/admin-guide/kernel-parameters.txt already provides an > explanation on memory_hotplug.memmap_on_memory parameter that states > that the feature cannot be enabled when using hugetlb-vmemmap > optimization. > > Users can always check whether the feature is enabled via > /sys/modules/memory_hotplug/parameters/memmap_on_memory. If memory_hotplug.memmap_on_memory is enabled $ cat /sys/module/memory_hotplug/parameters/memmap_on_memory $ Y If memory_hotplug.memmap_on_memory is disabled $ cat /sys/module/memory_hotplug/parameters/memmap_on_memory $ N > > Also, I did not check if it is, but if not, the fact about hugetlb-vmemmmap vs > hotplug-vmemmap should also be called out in the hugetlb-vmemmap kernel > parameter. Make sense. I will update the doc. Thanks. > > Thanks > > -- > Oscar Salvador > SUSE L3
On Wed, Apr 21, 2021 at 11:41:24AM +0800, Muchun Song wrote: > > Documentation/admin-guide/kernel-parameters.txt already provides an > > explanation on memory_hotplug.memmap_on_memory parameter that states > > that the feature cannot be enabled when using hugetlb-vmemmap > > optimization. > > > > Users can always check whether the feature is enabled via > > /sys/modules/memory_hotplug/parameters/memmap_on_memory. Heh, I realized this is not completely true. Users can check whether the feature is __enabled__ by checking the sys fs, but although it is enabled, it might not be effective. This might be due to a different number of reasons, vmemmap does not fully span a PMD, the size we want to add spans more than a single memory block, etc. That is what "Note that even when enabled, there are a few cases where the feature is not effective." is supposed to mean. Anyway, I did not change my opionion on this. Thanks
On Wed, Apr 21, 2021 at 3:33 PM Oscar Salvador <osalvador@suse.de> wrote: > > On Wed, Apr 21, 2021 at 11:41:24AM +0800, Muchun Song wrote: > > > Documentation/admin-guide/kernel-parameters.txt already provides an > > > explanation on memory_hotplug.memmap_on_memory parameter that states > > > that the feature cannot be enabled when using hugetlb-vmemmap > > > optimization. > > > > > > Users can always check whether the feature is enabled via > > > /sys/modules/memory_hotplug/parameters/memmap_on_memory. > > Heh, I realized this is not completely true. > Users can check whether the feature is __enabled__ by checking the sys fs, > but although it is enabled, it might not be effective. Right. I have done the test. > > This might be due to a different number of reasons, vmemmap does not fully > span a PMD, the size we want to add spans more than a single memory block, etc. Agree. Thanks for your explanations. > > That is what > > "Note that even when enabled, there are a few cases where the feature is not > effective." > > is supposed to mean. > > Anyway, I did not change my opionion on this. > > Thanks > > -- > Oscar Salvador > SUSE L3
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 9e655f5206ac..1f648b3e6120 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -2893,6 +2893,10 @@ Note that even when enabled, there are a few cases where the feature is not effective. + This is not compatible with hugetlb_free_vmemmap. If + both parameters are enabled, hugetlb_free_vmemmap takes + precedence over memory_hotplug.memmap_on_memory. + memtest= [KNL,X86,ARM,PPC,RISCV] Enable memtest Format: <integer> default : 0 <disable> diff --git a/drivers/acpi/acpi_memhotplug.c b/drivers/acpi/acpi_memhotplug.c index 8cc195c4c861..0d7f595ee441 100644 --- a/drivers/acpi/acpi_memhotplug.c +++ b/drivers/acpi/acpi_memhotplug.c @@ -15,6 +15,7 @@ #include <linux/acpi.h> #include <linux/memory.h> #include <linux/memory_hotplug.h> +#include <linux/hugetlb.h> #include "internal.h" diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c index 68923c19bdea..c45ed6c0cd9f 100644 --- a/mm/memory_hotplug.c +++ b/mm/memory_hotplug.c @@ -981,6 +981,7 @@ static int online_memory_block(struct memory_block *mem, void *arg) bool mhp_supports_memmap_on_memory(unsigned long size) { + bool supported; unsigned long nr_vmemmap_pages = size / PAGE_SIZE; unsigned long vmemmap_size = nr_vmemmap_pages * sizeof(struct page); unsigned long remaining_size = size - vmemmap_size; @@ -1011,11 +1012,18 @@ bool mhp_supports_memmap_on_memory(unsigned long size) * altmap as an alternative source of memory, and we do not exactly * populate a single PMD. */ - return memmap_on_memory && - IS_ENABLED(CONFIG_MHP_MEMMAP_ON_MEMORY) && - size == memory_block_size_bytes() && - IS_ALIGNED(vmemmap_size, PMD_SIZE) && - IS_ALIGNED(remaining_size, pageblock_nr_pages << PAGE_SHIFT); + supported = memmap_on_memory && + IS_ENABLED(CONFIG_MHP_MEMMAP_ON_MEMORY) && + size == memory_block_size_bytes() && + IS_ALIGNED(vmemmap_size, PMD_SIZE) && + IS_ALIGNED(remaining_size, pageblock_nr_pages << PAGE_SHIFT); + + if (supported && is_hugetlb_free_vmemmap_enabled()) { + pr_info("Cannot enable memory_hotplug.memmap_on_memory, it is not compatible with hugetlb_free_vmemmap\n"); + supported = false; + } + + return supported; } /*
The parameter of memory_hotplug.memmap_on_memory is not compatible with hugetlb_free_vmemmap. So disable it when hugetlb_free_vmemmap is enabled. Signed-off-by: Muchun Song <songmuchun@bytedance.com> --- Documentation/admin-guide/kernel-parameters.txt | 4 ++++ drivers/acpi/acpi_memhotplug.c | 1 + mm/memory_hotplug.c | 18 +++++++++++++----- 3 files changed, 18 insertions(+), 5 deletions(-)