Messages in this thread Patch in this message | | | From | Leonardo Bras <> | Subject | [PATCH 3/3] powerpc/mm/hash: Avoid multiple HPT resize-downs on memory hotunplug | Date | Fri, 12 Mar 2021 04:29:41 -0300 |
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During memory hotunplug, after each LMB is removed, the HPT may be resized-down if it would map a max of 4 times the current amount of memory. (2 shifts, due to introduced histeresis)
It usually is not an issue, but it can take a lot of time if HPT resizing-down fails. This happens because resize-down failures usually repeat at each LMB removal, until there are no more bolted entries conflict, which can take a while to happen.
This can be solved by doing a single HPT resize at the end of memory hotunplug, after all requested entries are removed.
To make this happen, it's necessary to temporarily disable all HPT resize-downs before hotunplug, re-enable them after hotunplug ends, and then resize-down HPT to the current memory size.
As an example, hotunplugging 256GB from a 385GB guest took 621s without this patch, and 100s after applied.
Signed-off-by: Leonardo Bras <leobras.c@gmail.com> --- arch/powerpc/include/asm/book3s/64/hash.h | 2 ++ arch/powerpc/include/asm/sparsemem.h | 2 ++ arch/powerpc/mm/book3s64/hash_utils.c | 28 +++++++++++++++++++ arch/powerpc/mm/book3s64/pgtable.c | 12 ++++++++ .../platforms/pseries/hotplug-memory.c | 16 +++++++++++ 5 files changed, 60 insertions(+)
diff --git a/arch/powerpc/include/asm/book3s/64/hash.h b/arch/powerpc/include/asm/book3s/64/hash.h index 843b0a178590..f92697c107f7 100644 --- a/arch/powerpc/include/asm/book3s/64/hash.h +++ b/arch/powerpc/include/asm/book3s/64/hash.h @@ -256,6 +256,8 @@ int hash__create_section_mapping(unsigned long start, unsigned long end, int hash__remove_section_mapping(unsigned long start, unsigned long end); void hash_memory_batch_expand_prepare(unsigned long newsize); +void hash_memory_batch_shrink_begin(void); +void hash_memory_batch_shrink_end(void); #endif /* !__ASSEMBLY__ */ #endif /* __KERNEL__ */ diff --git a/arch/powerpc/include/asm/sparsemem.h b/arch/powerpc/include/asm/sparsemem.h index 16b5f5300c84..a7a8a0d070fc 100644 --- a/arch/powerpc/include/asm/sparsemem.h +++ b/arch/powerpc/include/asm/sparsemem.h @@ -18,6 +18,8 @@ extern int memory_add_physaddr_to_nid(u64 start); #define memory_add_physaddr_to_nid memory_add_physaddr_to_nid void memory_batch_expand_prepare(unsigned long newsize); +void memory_batch_shrink_begin(void); +void memory_batch_shrink_end(void); #ifdef CONFIG_NUMA extern int hot_add_scn_to_nid(unsigned long scn_addr); diff --git a/arch/powerpc/mm/book3s64/hash_utils.c b/arch/powerpc/mm/book3s64/hash_utils.c index 1f6aa0bf27e7..e16f207de8e4 100644 --- a/arch/powerpc/mm/book3s64/hash_utils.c +++ b/arch/powerpc/mm/book3s64/hash_utils.c @@ -794,6 +794,9 @@ static unsigned long __init htab_get_table_size(void) } #ifdef CONFIG_MEMORY_HOTPLUG + +atomic_t hpt_resize_disable = ATOMIC_INIT(0); + static int resize_hpt_for_hotplug(unsigned long new_mem_size, bool shrinking) { unsigned target_hpt_shift; @@ -805,6 +808,10 @@ static int resize_hpt_for_hotplug(unsigned long new_mem_size, bool shrinking) if (shrinking) { + /* When batch removing entries, only resizes HPT at the end. */ + if (atomic_read_acquire(&hpt_resize_disable)) + return 0; + /* * To avoid lots of HPT resizes if memory size is fluctuating * across a boundary, we deliberately have some hysterisis @@ -872,6 +879,27 @@ void hash_memory_batch_expand_prepare(unsigned long newsize) pr_warn("Hash collision while resizing HPT\n"); } } + +void hash_memory_batch_shrink_begin(void) +{ + /* Disable HPT resize-down during hot-unplug */ + atomic_set_release(&hpt_resize_disable, 1); +} + +void hash_memory_batch_shrink_end(void) +{ + unsigned long newsize; + + /* Re-enables HPT resize-down after hot-unplug */ + atomic_set_release(&hpt_resize_disable, 0); + + newsize = memblock_phys_mem_size(); + /* Resize to smallest SHIFT possible */ + while (resize_hpt_for_hotplug(newsize, true) == -ENOSPC) { + newsize *= 2; + pr_warn("Hash collision while resizing HPT\n"); + } +} #endif /* CONFIG_MEMORY_HOTPLUG */ static void __init hash_init_partition_table(phys_addr_t hash_table, diff --git a/arch/powerpc/mm/book3s64/pgtable.c b/arch/powerpc/mm/book3s64/pgtable.c index f1cd8af0f67f..e01681e22e00 100644 --- a/arch/powerpc/mm/book3s64/pgtable.c +++ b/arch/powerpc/mm/book3s64/pgtable.c @@ -199,6 +199,18 @@ void memory_batch_expand_prepare(unsigned long newsize) if (!radix_enabled()) hash_memory_batch_expand_prepare(newsize); } + +void memory_batch_shrink_begin(void) +{ + if (!radix_enabled()) + hash_memory_batch_shrink_begin(); +} + +void memory_batch_shrink_end(void) +{ + if (!radix_enabled()) + hash_memory_batch_shrink_end(); +} #endif /* CONFIG_MEMORY_HOTPLUG */ void __init mmu_partition_table_init(void) diff --git a/arch/powerpc/platforms/pseries/hotplug-memory.c b/arch/powerpc/platforms/pseries/hotplug-memory.c index 353c71249214..9182fb5b5c01 100644 --- a/arch/powerpc/platforms/pseries/hotplug-memory.c +++ b/arch/powerpc/platforms/pseries/hotplug-memory.c @@ -425,6 +425,8 @@ static int dlpar_memory_remove_by_count(u32 lmbs_to_remove) return -EINVAL; } + memory_batch_shrink_begin(); + for_each_drmem_lmb(lmb) { rc = dlpar_remove_lmb(lmb); if (rc) @@ -470,6 +472,8 @@ static int dlpar_memory_remove_by_count(u32 lmbs_to_remove) rc = 0; } + memory_batch_shrink_end(); + return rc; } @@ -481,6 +485,8 @@ static int dlpar_memory_remove_by_index(u32 drc_index) pr_debug("Attempting to hot-remove LMB, drc index %x\n", drc_index); + memory_batch_shrink_begin(); + lmb_found = 0; for_each_drmem_lmb(lmb) { if (lmb->drc_index == drc_index) { @@ -502,6 +508,8 @@ static int dlpar_memory_remove_by_index(u32 drc_index) else pr_debug("Memory at %llx was hot-removed\n", lmb->base_addr); + memory_batch_shrink_end(); + return rc; } @@ -532,6 +540,8 @@ static int dlpar_memory_remove_by_ic(u32 lmbs_to_remove, u32 drc_index) if (lmbs_available < lmbs_to_remove) return -EINVAL; + memory_batch_shrink_begin(); + for_each_drmem_lmb_in_range(lmb, start_lmb, end_lmb) { if (!(lmb->flags & DRCONF_MEM_ASSIGNED)) continue; @@ -572,6 +582,8 @@ static int dlpar_memory_remove_by_ic(u32 lmbs_to_remove, u32 drc_index) } } + memory_batch_shrink_end(); + return rc; } @@ -700,6 +712,7 @@ static int dlpar_memory_add_by_count(u32 lmbs_to_add) if (lmbs_added != lmbs_to_add) { pr_err("Memory hot-add failed, removing any added LMBs\n"); + memory_batch_shrink_begin(); for_each_drmem_lmb(lmb) { if (!drmem_lmb_reserved(lmb)) continue; @@ -713,6 +726,7 @@ static int dlpar_memory_add_by_count(u32 lmbs_to_add) drmem_remove_lmb_reservation(lmb); } + memory_batch_shrink_end(); rc = -EINVAL; } else { for_each_drmem_lmb(lmb) { @@ -814,6 +828,7 @@ static int dlpar_memory_add_by_ic(u32 lmbs_to_add, u32 drc_index) if (rc) { pr_err("Memory indexed-count-add failed, removing any added LMBs\n"); + memory_batch_shrink_begin(); for_each_drmem_lmb_in_range(lmb, start_lmb, end_lmb) { if (!drmem_lmb_reserved(lmb)) continue; @@ -827,6 +842,7 @@ static int dlpar_memory_add_by_ic(u32 lmbs_to_add, u32 drc_index) drmem_remove_lmb_reservation(lmb); } + memory_batch_shrink_end(); rc = -EINVAL; } else { for_each_drmem_lmb_in_range(lmb, start_lmb, end_lmb) { -- 2.29.2
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