Messages in this thread | | | Date | Thu, 23 Jul 2020 09:00:58 +1000 | From | Anton Blanchard <> | Subject | Re: [PATCH v2 1/2] powerpc/drmem: accelerate memory_add_physaddr_to_nid() with LMB xarray |
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Hi Scott,
I'm hitting this issue and Rick just pointed my at your patch. Any chance we could get it upstream?
Thanks, Anton
> On PowerPC, memory_add_physaddr_to_nid() uses a linear search to find > an LMB matching the given address. This scales very poorly when there > are many LMBs. The poor scaling cripples drmem_init() during boot: > lmb_set_nid(), which calls memory_add_physaddr_to_nid(), is called for > each LMB. > > If we index each LMB in an xarray by its base address we can achieve > O(log n) search during memory_add_physaddr_to_nid(), which scales much > better. > > For example, in the lab we have a 64TB P9 machine with 256MB LMBs. > So, suring drmem_init() we instantiate 249854 LMBs. On a vanilla > kernel it completes drmem_init() in ~35 seconds with a soft lockup > trace. On the patched kernel it completes drmem_init() in ~0.5 > seconds. > > Before: > [ 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) > > After: > [ 53.424702] drmem: initializing drmem v2 > [ 53.898813] drmem: 249854 LMB(s) > > lmb_set_nid() is called from dlpar_lmb_add() so this patch will also > improve memory hot-add speeds on big machines. > > Signed-off-by: Scott Cheloha <cheloha@linux.ibm.com> > --- > arch/powerpc/include/asm/drmem.h | 1 + > arch/powerpc/mm/drmem.c | 24 ++++++++++++++++++++++++ > arch/powerpc/mm/numa.c | 29 ++++++++++------------------- > 3 files changed, 35 insertions(+), 19 deletions(-) > > diff --git a/arch/powerpc/include/asm/drmem.h > b/arch/powerpc/include/asm/drmem.h index 3d76e1c388c2..90a5a9ad872b > 100644 --- a/arch/powerpc/include/asm/drmem.h > +++ b/arch/powerpc/include/asm/drmem.h > @@ -88,6 +88,7 @@ static inline bool drmem_lmb_reserved(struct > drmem_lmb *lmb) return lmb->flags & DRMEM_LMB_RESERVED; > } > > +struct drmem_lmb *drmem_find_lmb_by_base_addr(u64 base_addr); > u64 drmem_lmb_memory_max(void); > void __init walk_drmem_lmbs(struct device_node *dn, > void (*func)(struct drmem_lmb *, const > __be32 **)); diff --git a/arch/powerpc/mm/drmem.c > b/arch/powerpc/mm/drmem.c index 44bfbdae920c..62cbe79e3860 100644 > --- a/arch/powerpc/mm/drmem.c > +++ b/arch/powerpc/mm/drmem.c > @@ -11,12 +11,31 @@ > #include <linux/of.h> > #include <linux/of_fdt.h> > #include <linux/memblock.h> > +#include <linux/xarray.h> > #include <asm/prom.h> > #include <asm/drmem.h> > > +static DEFINE_XARRAY(drmem_lmb_xa_base_addr); > static struct drmem_lmb_info __drmem_info; > struct drmem_lmb_info *drmem_info = &__drmem_info; > > +static int drmem_cache_lmb_for_lookup(struct drmem_lmb *lmb) > +{ > + void *ret; > + > + ret = xa_store(&drmem_lmb_xa_base_addr, lmb->base_addr, lmb, > + GFP_KERNEL); > + if (xa_is_err(ret)) > + return xa_err(ret); > + > + return 0; > +} > + > +struct drmem_lmb *drmem_find_lmb_by_base_addr(u64 base_addr) > +{ > + return xa_load(&drmem_lmb_xa_base_addr, base_addr); > +} > + > u64 drmem_lmb_memory_max(void) > { > struct drmem_lmb *last_lmb; > @@ -364,6 +383,8 @@ static void __init init_drmem_v1_lmbs(const > __be32 *prop) > for_each_drmem_lmb(lmb) { > read_drconf_v1_cell(lmb, &prop); > + if (drmem_cache_lmb_for_lookup(lmb) != 0) > + return; > lmb_set_nid(lmb); > } > } > @@ -411,6 +432,9 @@ static void __init init_drmem_v2_lmbs(const > __be32 *prop) lmb->aa_index = dr_cell.aa_index; > lmb->flags = dr_cell.flags; > > + if (drmem_cache_lmb_for_lookup(lmb) != 0) > + return; > + > lmb_set_nid(lmb); > } > } > diff --git a/arch/powerpc/mm/numa.c b/arch/powerpc/mm/numa.c > index 3c7dec70cda0..0fd7963a991e 100644 > --- a/arch/powerpc/mm/numa.c > +++ b/arch/powerpc/mm/numa.c > @@ -958,27 +958,18 @@ early_param("topology_updates", > early_topology_updates); static int > hot_add_drconf_scn_to_nid(unsigned long scn_addr) { > struct drmem_lmb *lmb; > - unsigned long lmb_size; > - int nid = NUMA_NO_NODE; > - > - lmb_size = drmem_lmb_size(); > - > - for_each_drmem_lmb(lmb) { > - /* skip this block if it is reserved or not assigned > to > - * this partition */ > - if ((lmb->flags & DRCONF_MEM_RESERVED) > - || !(lmb->flags & DRCONF_MEM_ASSIGNED)) > - continue; > - > - if ((scn_addr < lmb->base_addr) > - || (scn_addr >= (lmb->base_addr + lmb_size))) > - continue; > > - nid = of_drconf_to_nid_single(lmb); > - break; > - } > + lmb = drmem_find_lmb_by_base_addr(scn_addr); > + if (lmb == NULL) > + return NUMA_NO_NODE; > + > + /* can't use this block if it is reserved or not assigned to > + * this partition */ > + if ((lmb->flags & DRCONF_MEM_RESERVED) > + || !(lmb->flags & DRCONF_MEM_ASSIGNED)) > + return NUMA_NO_NODE; > > - return nid; > + return of_drconf_to_nid_single(lmb); > } > > /*
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