[PATCH v2] pseries/drmem: don't cache node id in drmem_lmb struct
From: Scott Cheloha <hidden>
Date: 2020-07-28 16:58:17
At memory hot-remove time we can retrieve an LMB's nid from its corresponding memory_block. There is no need to store the nid in multiple locations. Note that lmb_to_memblock() uses find_memory_block() to get the corresponding memory_block. As find_memory_block() runs in sub-linear time this approach is negligibly slower than what we do at present. In exchange for this lookup at hot-remove time we no longer need to call memory_add_physaddr_to_nid() during drmem_init() for each LMB. On powerpc, memory_add_physaddr_to_nid() is a linear search, so this spares us an O(n^2) initialization during boot. On systems with many LMBs that initialization overhead is palpable and disruptive. For example, on a box with 249854 LMBs we're seeing drmem_init() take upwards of 30 seconds to complete: [ 53.721639] drmem: initializing drmem v2 [ 80.604346] watchdog: BUG: soft lockup - CPU#65 stuck for 23s! [swapper/0:1] [ 80.604377] Modules linked in: [ 80.604389] CPU: 65 PID: 1 Comm: swapper/0 Not tainted 5.6.0-rc2+ #4 [ 80.604397] NIP: c0000000000a4980 LR: c0000000000a4940 CTR: 0000000000000000 [ 80.604407] REGS: c0002dbff8493830 TRAP: 0901 Not tainted (5.6.0-rc2+) [ 80.604412] MSR: 8000000002009033 <SF,VEC,EE,ME,IR,DR,RI,LE> CR: 44000248 XER: 0000000d [ 80.604431] CFAR: c0000000000a4a38 IRQMASK: 0 [ 80.604431] GPR00: c0000000000a4940 c0002dbff8493ac0 c000000001904400 c0003cfffffede30 [ 80.604431] GPR04: 0000000000000000 c000000000f4095a 000000000000002f 0000000010000000 [ 80.604431] GPR08: c0000bf7ecdb7fb8 c0000bf7ecc2d3c8 0000000000000008 c00c0002fdfb2001 [ 80.604431] GPR12: 0000000000000000 c00000001e8ec200 [ 80.604477] NIP [c0000000000a4980] hot_add_scn_to_nid+0xa0/0x3e0 [ 80.604486] LR [c0000000000a4940] hot_add_scn_to_nid+0x60/0x3e0 [ 80.604492] Call Trace: [ 80.604498] [c0002dbff8493ac0] [c0000000000a4940] hot_add_scn_to_nid+0x60/0x3e0 (unreliable) [ 80.604509] [c0002dbff8493b20] [c000000000087c10] memory_add_physaddr_to_nid+0x20/0x60 [ 80.604521] [c0002dbff8493b40] [c0000000010d4880] drmem_init+0x25c/0x2f0 [ 80.604530] [c0002dbff8493c10] [c000000000010154] do_one_initcall+0x64/0x2c0 [ 80.604540] [c0002dbff8493ce0] [c0000000010c4aa0] kernel_init_freeable+0x2d8/0x3a0 [ 80.604550] [c0002dbff8493db0] [c000000000010824] kernel_init+0x2c/0x148 [ 80.604560] [c0002dbff8493e20] [c00000000000b648] ret_from_kernel_thread+0x5c/0x74 [ 80.604567] Instruction dump: [ 80.604574] 392918e8 e9490000 e90a000a e92a0000 80ea000c 1d080018 3908ffe8 7d094214 [ 80.604586] 7fa94040 419d00dc e9490010 714a0088 <2faa0008> 409e00ac e9490000 7fbe5040 [ 89.047390] drmem: 249854 LMB(s) With a patched kernel on the same machine we're no longer seeing the soft lockup. drmem_init() now completes in negligible time, even when the LMB count is large. Signed-off-by: Scott Cheloha <redacted> --- arch/powerpc/include/asm/drmem.h | 21 ------------------- arch/powerpc/mm/drmem.c | 6 +----- .../platforms/pseries/hotplug-memory.c | 19 ++++++++++------- 3 files changed, 13 insertions(+), 33 deletions(-)
diff --git a/arch/powerpc/include/asm/drmem.h b/arch/powerpc/include/asm/drmem.h
index 414d209f45bb..34e4e9b257f5 100644
--- a/arch/powerpc/include/asm/drmem.h
+++ b/arch/powerpc/include/asm/drmem.h@@ -13,9 +13,6 @@ struct drmem_lmb { u32 drc_index; u32 aa_index; u32 flags; -#ifdef CONFIG_MEMORY_HOTPLUG - int nid; -#endif }; struct drmem_lmb_info {
@@ -104,22 +101,4 @@ static inline void invalidate_lmb_associativity_index(struct drmem_lmb *lmb) lmb->aa_index = 0xffffffff; } -#ifdef CONFIG_MEMORY_HOTPLUG -static inline void lmb_set_nid(struct drmem_lmb *lmb) -{ - lmb->nid = memory_add_physaddr_to_nid(lmb->base_addr); -} -static inline void lmb_clear_nid(struct drmem_lmb *lmb) -{ - lmb->nid = -1; -} -#else -static inline void lmb_set_nid(struct drmem_lmb *lmb) -{ -} -static inline void lmb_clear_nid(struct drmem_lmb *lmb) -{ -} -#endif - #endif /* _ASM_POWERPC_LMB_H */
diff --git a/arch/powerpc/mm/drmem.c b/arch/powerpc/mm/drmem.c
index 59327cefbc6a..873fcfc7b875 100644
--- a/arch/powerpc/mm/drmem.c
+++ b/arch/powerpc/mm/drmem.c@@ -362,10 +362,8 @@ static void __init init_drmem_v1_lmbs(const __be32 *prop) if (!drmem_info->lmbs) return; - for_each_drmem_lmb(lmb) { + for_each_drmem_lmb(lmb) read_drconf_v1_cell(lmb, &prop); - lmb_set_nid(lmb); - } } static void __init init_drmem_v2_lmbs(const __be32 *prop)
@@ -410,8 +408,6 @@ static void __init init_drmem_v2_lmbs(const __be32 *prop) lmb->aa_index = dr_cell.aa_index; lmb->flags = dr_cell.flags; - - lmb_set_nid(lmb); } } }
diff --git a/arch/powerpc/platforms/pseries/hotplug-memory.c b/arch/powerpc/platforms/pseries/hotplug-memory.c
index 5ace2f9a277e..7bf66fdcf916 100644
--- a/arch/powerpc/platforms/pseries/hotplug-memory.c
+++ b/arch/powerpc/platforms/pseries/hotplug-memory.c@@ -356,25 +356,29 @@ static int dlpar_add_lmb(struct drmem_lmb *); static int dlpar_remove_lmb(struct drmem_lmb *lmb) { + struct memory_block *mem_block; unsigned long block_sz; int rc; if (!lmb_is_removable(lmb)) return -EINVAL; + mem_block = lmb_to_memblock(lmb); + if (mem_block == NULL) + return -EINVAL; + rc = dlpar_offline_lmb(lmb); if (rc) return rc; block_sz = pseries_memory_block_size(); - __remove_memory(lmb->nid, lmb->base_addr, block_sz); + __remove_memory(mem_block->nid, lmb->base_addr, block_sz); /* Update memory regions for memory remove */ memblock_remove(lmb->base_addr, block_sz); invalidate_lmb_associativity_index(lmb); - lmb_clear_nid(lmb); lmb->flags &= ~DRCONF_MEM_ASSIGNED; return 0;
@@ -631,7 +635,7 @@ static int dlpar_memory_remove_by_ic(u32 lmbs_to_remove, u32 drc_index) static int dlpar_add_lmb(struct drmem_lmb *lmb) { unsigned long block_sz; - int rc; + int nid, rc; if (lmb->flags & DRCONF_MEM_ASSIGNED) return -EINVAL;
@@ -642,11 +646,13 @@ static int dlpar_add_lmb(struct drmem_lmb *lmb) return rc; } - lmb_set_nid(lmb); block_sz = memory_block_size_bytes(); + /* Find the node id for this address. */ + nid = memory_add_physaddr_to_nid(lmb->base_addr); + /* Add the memory */ - rc = __add_memory(lmb->nid, lmb->base_addr, block_sz); + rc = __add_memory(nid, lmb->base_addr, block_sz); if (rc) { invalidate_lmb_associativity_index(lmb); return rc;
@@ -654,9 +660,8 @@ static int dlpar_add_lmb(struct drmem_lmb *lmb) rc = dlpar_online_lmb(lmb); if (rc) { - __remove_memory(lmb->nid, lmb->base_addr, block_sz); + __remove_memory(nid, lmb->base_addr, block_sz); invalidate_lmb_associativity_index(lmb); - lmb_clear_nid(lmb); } else { lmb->flags |= DRCONF_MEM_ASSIGNED; }
--
2.24.1