On Fri, Apr 30, 2021 at 11:36:08AM -0300, Leonardo Bras wrote: > Every time a memory hotplug happens, and the memory limit crosses a 2^n > value, it may be necessary to perform HPT resizing-up, which can take > some time (over 100ms in my tests). > > It usually is not an issue, but it can take some time if a lot of memory > is added to a guest with little starting memory: > Adding 256G to a 2GB guest, for example will require 8 HPT resizes. > > Perform an HPT resize before memory hotplug, updating HPT to its > final size (considering a successful hotplug), taking the number of > HPT resizes to at most one per memory hotplug action. > > Signed-off-by: Leonardo Bras <leobra...@gmail.com>
Reviewed-by: David Gibson <da...@gibson.dropbear.id.au>
> ---
> arch/powerpc/include/asm/book3s/64/hash.h | 2 ++
> arch/powerpc/mm/book3s64/hash_utils.c | 20 +++++++++++++++++++
> .../platforms/pseries/hotplug-memory.c | 9 +++++++++
> 3 files changed, 31 insertions(+)
>
> diff --git a/arch/powerpc/include/asm/book3s/64/hash.h
> b/arch/powerpc/include/asm/book3s/64/hash.h
> index d959b0195ad9..fad4af8b8543 100644
> --- a/arch/powerpc/include/asm/book3s/64/hash.h
> +++ b/arch/powerpc/include/asm/book3s/64/hash.h
> @@ -255,6 +255,8 @@ int hash__create_section_mapping(unsigned long start,
> unsigned long end,
> int nid, pgprot_t prot);
> int hash__remove_section_mapping(unsigned long start, unsigned long end);
>
> +void hash_batch_expand_prepare(unsigned long newsize);
> +
> #endif /* !__ASSEMBLY__ */
> #endif /* __KERNEL__ */
> #endif /* _ASM_POWERPC_BOOK3S_64_HASH_H */
> diff --git a/arch/powerpc/mm/book3s64/hash_utils.c
> b/arch/powerpc/mm/book3s64/hash_utils.c
> index 608e4ed397a9..3fa395b3fe57 100644
> --- a/arch/powerpc/mm/book3s64/hash_utils.c
> +++ b/arch/powerpc/mm/book3s64/hash_utils.c
> @@ -859,6 +859,26 @@ int hash__remove_section_mapping(unsigned long start,
> unsigned long end)
>
> return rc;
> }
> +
> +void hash_batch_expand_prepare(unsigned long newsize)
> +{
> + const u64 starting_size = ppc64_pft_size;
> +
> + /*
> + * Resizing-up HPT should never fail, but there are some cases system
> starts with higher
> + * SHIFT than required, and we go through the funny case of resizing
> HPT down while
> + * adding memory
> + */
> +
> + while (resize_hpt_for_hotplug(newsize, false) == -ENOSPC) {
> + newsize *= 2;
> + pr_warn("Hash collision while resizing HPT\n");
> +
> + /* Do not try to resize to the starting size, or bigger value */
> + if (htab_shift_for_mem_size(newsize) >= starting_size)
> + break;
> + }
> +}
> #endif /* CONFIG_MEMORY_HOTPLUG */
>
> static void __init hash_init_partition_table(phys_addr_t hash_table,
> diff --git a/arch/powerpc/platforms/pseries/hotplug-memory.c
> b/arch/powerpc/platforms/pseries/hotplug-memory.c
> index 8377f1f7c78e..48b2cfe4ce69 100644
> --- a/arch/powerpc/platforms/pseries/hotplug-memory.c
> +++ b/arch/powerpc/platforms/pseries/hotplug-memory.c
> @@ -13,6 +13,7 @@
> #include <linux/memory.h>
> #include <linux/memory_hotplug.h>
> #include <linux/slab.h>
> +#include <linux/pgtable.h>
>
> #include <asm/firmware.h>
> #include <asm/machdep.h>
> @@ -671,6 +672,10 @@ static int dlpar_memory_add_by_count(u32 lmbs_to_add)
> if (lmbs_available < lmbs_to_add)
> return -EINVAL;
>
> + if (!radix_enabled())
> + hash_batch_expand_prepare(memblock_phys_mem_size() +
> + lmbs_to_add *
> drmem_lmb_size());
> +
> for_each_drmem_lmb(lmb) {
> if (lmb->flags & DRCONF_MEM_ASSIGNED)
> continue;
> @@ -788,6 +793,10 @@ static int dlpar_memory_add_by_ic(u32 lmbs_to_add, u32
> drc_index)
> if (lmbs_available < lmbs_to_add)
> return -EINVAL;
>
> + if (!radix_enabled())
> + hash_batch_expand_prepare(memblock_phys_mem_size() +
> + lmbs_to_add * drmem_lmb_size());
> +
> for_each_drmem_lmb_in_range(lmb, start_lmb, end_lmb) {
> if (lmb->flags & DRCONF_MEM_ASSIGNED)
> continue;
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
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