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* [PATCH v2] pseries/drmem: don't cache node id in drmem_lmb struct
@ 2020-07-28 16:53 Scott Cheloha
  2020-07-28 18:22 ` David Hildenbrand
  2020-07-29 15:32 ` Laurent Dufour
  0 siblings, 2 replies; 3+ messages in thread
From: Scott Cheloha @ 2020-07-28 16:53 UTC (permalink / raw)
  To: linuxppc-dev
  Cc: Nathan Lynch, Laurent Dufour, David Hildenbrand, Michal Suchanek,
	Rick Lindsley

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 <cheloha@linux.ibm.com>
---
 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


^ permalink raw reply	[flat|nested] 3+ messages in thread

* Re: [PATCH v2] pseries/drmem: don't cache node id in drmem_lmb struct
  2020-07-28 16:53 [PATCH v2] pseries/drmem: don't cache node id in drmem_lmb struct Scott Cheloha
@ 2020-07-28 18:22 ` David Hildenbrand
  2020-07-29 15:32 ` Laurent Dufour
  1 sibling, 0 replies; 3+ messages in thread
From: David Hildenbrand @ 2020-07-28 18:22 UTC (permalink / raw)
  To: Scott Cheloha, linuxppc-dev
  Cc: Nathan Lynch, Michal Suchanek, Laurent Dufour, Rick Lindsley

On 28.07.20 18:53, Scott Cheloha wrote:
> 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.
> 

Yeah, as long as you remove_memory() in memory block granularity, this
is guaranteed to work.

Reviewed-by: David Hildenbrand <david@redhat.com>


-- 
Thanks,

David / dhildenb


^ permalink raw reply	[flat|nested] 3+ messages in thread

* Re: [PATCH v2] pseries/drmem: don't cache node id in drmem_lmb struct
  2020-07-28 16:53 [PATCH v2] pseries/drmem: don't cache node id in drmem_lmb struct Scott Cheloha
  2020-07-28 18:22 ` David Hildenbrand
@ 2020-07-29 15:32 ` Laurent Dufour
  1 sibling, 0 replies; 3+ messages in thread
From: Laurent Dufour @ 2020-07-29 15:32 UTC (permalink / raw)
  To: Scott Cheloha, linuxppc-dev
  Cc: Nathan Lynch, Michal Suchanek, David Hildenbrand, Rick Lindsley

Hi Scott,

Le 28/07/2020 à 18:53, Scott Cheloha a écrit :
> 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 <cheloha@linux.ibm.com>
> ---
>   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;
> +

lmb_to_memblock is 'getting' the memblock's device, so you should call 
put_device(mem_block->device) to reverse that operation.

Something like:

--- a/arch/powerpc/platforms/pseries/hotplug-memory.c
+++ b/arch/powerpc/platforms/pseries/hotplug-memory.c
@@ -367,7 +367,7 @@ static int dlpar_remove_lmb(struct drmem_lmb *lmb)

  	rc = dlpar_offline_lmb(lmb);
  	if (rc)
-		return rc;
+		goto out;

  	block_sz = pseries_memory_block_size();

@@ -379,7 +379,9 @@ static int dlpar_remove_lmb(struct drmem_lmb *lmb)
  	invalidate_lmb_associativity_index(lmb);
  	lmb->flags &= ~DRCONF_MEM_ASSIGNED;

-	return 0;
+out:
+	put_device(&mem_block->dev);
+	return rc;
  }

  static int dlpar_memory_remove_by_count(u32 lmbs_to_remove)



>   	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);

This function is calling hot_add_drconf_scn_to_nid() which is walking all the 
LMBs linearly, so we may spend a lot of time here.

I think it be nice to take some breath in the caller's loop in 
dlpar_memory_add_by_count() to avoid soft lockup to be raised there when adding 
a large number of LMBs, isn't it?

Nathan sent a patch to add such a breath in for_each_drmem_lmb_in_range() may be 
it would be nice to add one in dlpar_memory_add_by_count() through that patch.

> +
>   	/* 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;
>   	}
> 


^ permalink raw reply	[flat|nested] 3+ messages in thread

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Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2020-07-28 16:53 [PATCH v2] pseries/drmem: don't cache node id in drmem_lmb struct Scott Cheloha
2020-07-28 18:22 ` David Hildenbrand
2020-07-29 15:32 ` Laurent Dufour

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