| Message ID | 20120228135326.GE1702@cmpxchg.org (mailing list archive) |
|---|---|
| State | Not Applicable |
| Headers | show |
On 28.02.2012 [14:53:26 +0100], Johannes Weiner wrote: > On Fri, Feb 24, 2012 at 11:33:58AM -0800, Nishanth Aravamudan wrote: > > While testing AMS (Active Memory Sharing) / CMO (Cooperative Memory > > Overcommit) on powerpc, we tripped the following: > > > > kernel BUG at mm/bootmem.c:483! > > cpu 0x0: Vector: 700 (Program Check) at [c000000000c03940] > > pc: c000000000a62bd8: .alloc_bootmem_core+0x90/0x39c > > lr: c000000000a64bcc: .sparse_early_usemaps_alloc_node+0x84/0x29c > > sp: c000000000c03bc0 > > msr: 8000000000021032 > > current = 0xc000000000b0cce0 > > paca = 0xc000000001d80000 > > pid = 0, comm = swapper > > kernel BUG at mm/bootmem.c:483! > > enter ? for help > > [c000000000c03c80] c000000000a64bcc > > .sparse_early_usemaps_alloc_node+0x84/0x29c > > [c000000000c03d50] c000000000a64f10 .sparse_init+0x12c/0x28c > > [c000000000c03e20] c000000000a474f4 .setup_arch+0x20c/0x294 > > [c000000000c03ee0] c000000000a4079c .start_kernel+0xb4/0x460 > > [c000000000c03f90] c000000000009670 .start_here_common+0x1c/0x2c > > > > This is > > > > BUG_ON(limit && goal + size > limit); > > > > and after some debugging, it seems that > > > > goal = 0x7ffff000000 > > limit = 0x80000000000 > > > > and sparse_early_usemaps_alloc_node -> > > sparse_early_usemaps_alloc_pgdat_section -> alloc_bootmem_section calls > > > > return alloc_bootmem_section(usemap_size() * count, section_nr); > > > > This is on a system with 8TB available via the AMS pool, and as a quirk > > of AMS in firmware, all of that memory shows up in node 0. So, we end up > > with an allocation that will fail the goal/limit constraints. In theory, > > we could "fall-back" to alloc_bootmem_node() in > > sparse_early_usemaps_alloc_node(), but since we actually have HOTREMOVE > > defined, we'll BUG_ON() instead. A simple solution appears to be to > > disable the limit check if the size of the allocation in > > alloc_bootmem_secition exceeds the section size. > > It makes sense to allow the usemaps to spill over to subsequent > sections instead of panicking, so FWIW: > > Acked-by: Johannes Weiner <hannes@cmpxchg.org> > > That being said, it would be good if check_usemap_section_nr() printed > the cross-dependencies between pgdats and sections when the usemaps of > a node spilled over to other sections than the ones holding the pgdat. > > How about this? > > --- > From: Johannes Weiner <hannes@cmpxchg.org> > Subject: sparsemem/bootmem: catch greater than section size allocations fix > > If alloc_bootmem_section() no longer guarantees section-locality, we > need check_usemap_section_nr() to print possible cross-dependencies > between node descriptors and the usemaps allocated through it. > > Signed-off-by: Johannes Weiner <hannes@cmpxchg.org> > --- > > diff --git a/mm/sparse.c b/mm/sparse.c > index 61d7cde..9e032dc 100644 > --- a/mm/sparse.c > +++ b/mm/sparse.c > @@ -359,6 +359,7 @@ static void __init sparse_early_usemaps_alloc_node(unsigned long**usemap_map, > continue; > usemap_map[pnum] = usemap; > usemap += size; > + check_usemap_section_nr(nodeid, usemap_map[pnum]); > } > return; > } This makes sense to me -- ok if I fold it into the re-worked patch (based upon Mel's comments)? > --- > > Furthermore, I wonder if we can remove the sparse-specific stuff from > bootmem.c as well, as now even more so than before, calculating the > desired area is really none of bootmem's business. > > Would something like this be okay? > > --- > From: Johannes Weiner <hannes@cmpxchg.org> > Subject: [patch] mm: remove sparsemem allocation details from the bootmem allocator > > alloc_bootmem_section() derives allocation area constraints from the > specified sparsemem section. This is a bit specific for a generic > memory allocator like bootmem, though, so move it over to sparsemem. > > Since __alloc_bootmem_node() already retries failed allocations with > relaxed area constraints, the fallback code in sparsemem.c can be > removed and the code becomes a bit more compact overall. > > Signed-off-by: Johannes Weiner <hannes@cmpxchg.org> I've not tested it, but the intention seems sensible. I think it should remain a separate change. Thanks, Nish
On Tue, Feb 28, 2012 at 12:11:51PM -0800, Nishanth Aravamudan wrote: > On 28.02.2012 [14:53:26 +0100], Johannes Weiner wrote: > > On Fri, Feb 24, 2012 at 11:33:58AM -0800, Nishanth Aravamudan wrote: > > > While testing AMS (Active Memory Sharing) / CMO (Cooperative Memory > > > Overcommit) on powerpc, we tripped the following: > > > > > > kernel BUG at mm/bootmem.c:483! > > > cpu 0x0: Vector: 700 (Program Check) at [c000000000c03940] > > > pc: c000000000a62bd8: .alloc_bootmem_core+0x90/0x39c > > > lr: c000000000a64bcc: .sparse_early_usemaps_alloc_node+0x84/0x29c > > > sp: c000000000c03bc0 > > > msr: 8000000000021032 > > > current = 0xc000000000b0cce0 > > > paca = 0xc000000001d80000 > > > pid = 0, comm = swapper > > > kernel BUG at mm/bootmem.c:483! > > > enter ? for help > > > [c000000000c03c80] c000000000a64bcc > > > .sparse_early_usemaps_alloc_node+0x84/0x29c > > > [c000000000c03d50] c000000000a64f10 .sparse_init+0x12c/0x28c > > > [c000000000c03e20] c000000000a474f4 .setup_arch+0x20c/0x294 > > > [c000000000c03ee0] c000000000a4079c .start_kernel+0xb4/0x460 > > > [c000000000c03f90] c000000000009670 .start_here_common+0x1c/0x2c > > > > > > This is > > > > > > BUG_ON(limit && goal + size > limit); > > > > > > and after some debugging, it seems that > > > > > > goal = 0x7ffff000000 > > > limit = 0x80000000000 > > > > > > and sparse_early_usemaps_alloc_node -> > > > sparse_early_usemaps_alloc_pgdat_section -> alloc_bootmem_section calls > > > > > > return alloc_bootmem_section(usemap_size() * count, section_nr); > > > > > > This is on a system with 8TB available via the AMS pool, and as a quirk > > > of AMS in firmware, all of that memory shows up in node 0. So, we end up > > > with an allocation that will fail the goal/limit constraints. In theory, > > > we could "fall-back" to alloc_bootmem_node() in > > > sparse_early_usemaps_alloc_node(), but since we actually have HOTREMOVE > > > defined, we'll BUG_ON() instead. A simple solution appears to be to > > > disable the limit check if the size of the allocation in > > > alloc_bootmem_secition exceeds the section size. > > > > It makes sense to allow the usemaps to spill over to subsequent > > sections instead of panicking, so FWIW: > > > > Acked-by: Johannes Weiner <hannes@cmpxchg.org> > > > > That being said, it would be good if check_usemap_section_nr() printed > > the cross-dependencies between pgdats and sections when the usemaps of > > a node spilled over to other sections than the ones holding the pgdat. > > > > How about this? > > > > --- > > From: Johannes Weiner <hannes@cmpxchg.org> > > Subject: sparsemem/bootmem: catch greater than section size allocations fix > > > > If alloc_bootmem_section() no longer guarantees section-locality, we > > need check_usemap_section_nr() to print possible cross-dependencies > > between node descriptors and the usemaps allocated through it. > > > > Signed-off-by: Johannes Weiner <hannes@cmpxchg.org> > > --- > > > > diff --git a/mm/sparse.c b/mm/sparse.c > > index 61d7cde..9e032dc 100644 > > --- a/mm/sparse.c > > +++ b/mm/sparse.c > > @@ -359,6 +359,7 @@ static void __init sparse_early_usemaps_alloc_node(unsigned long**usemap_map, > > continue; > > usemap_map[pnum] = usemap; > > usemap += size; > > + check_usemap_section_nr(nodeid, usemap_map[pnum]); > > } > > return; > > } > > This makes sense to me -- ok if I fold it into the re-worked patch > (based upon Mel's comments)? Sure thing! > > Furthermore, I wonder if we can remove the sparse-specific stuff from > > bootmem.c as well, as now even more so than before, calculating the > > desired area is really none of bootmem's business. > > > > Would something like this be okay? > > > > --- > > From: Johannes Weiner <hannes@cmpxchg.org> > > Subject: [patch] mm: remove sparsemem allocation details from the bootmem allocator > > > > alloc_bootmem_section() derives allocation area constraints from the > > specified sparsemem section. This is a bit specific for a generic > > memory allocator like bootmem, though, so move it over to sparsemem. > > > > Since __alloc_bootmem_node() already retries failed allocations with > > relaxed area constraints, the fallback code in sparsemem.c can be > > removed and the code becomes a bit more compact overall. > > > > Signed-off-by: Johannes Weiner <hannes@cmpxchg.org> > > I've not tested it, but the intention seems sensible. I think it should > remain a separate change. Yes, I agree. I'll resend it in a bit as stand-alone patch.
diff --git a/mm/sparse.c b/mm/sparse.c index 61d7cde..9e032dc 100644 --- a/mm/sparse.c +++ b/mm/sparse.c @@ -359,6 +359,7 @@ static void __init sparse_early_usemaps_alloc_node(unsigned long**usemap_map, continue; usemap_map[pnum] = usemap; usemap += size; + check_usemap_section_nr(nodeid, usemap_map[pnum]); } return; } --- Furthermore, I wonder if we can remove the sparse-specific stuff from bootmem.c as well, as now even more so than before, calculating the desired area is really none of bootmem's business. Would something like this be okay? --- From: Johannes Weiner <hannes@cmpxchg.org> Subject: [patch] mm: remove sparsemem allocation details from the bootmem allocator alloc_bootmem_section() derives allocation area constraints from the specified sparsemem section. This is a bit specific for a generic memory allocator like bootmem, though, so move it over to sparsemem. Since __alloc_bootmem_node() already retries failed allocations with relaxed area constraints, the fallback code in sparsemem.c can be removed and the code becomes a bit more compact overall. Signed-off-by: Johannes Weiner <hannes@cmpxchg.org> --- include/linux/bootmem.h | 3 --- mm/bootmem.c | 26 -------------------------- mm/sparse.c | 29 +++++++++-------------------- 3 files changed, 9 insertions(+), 49 deletions(-) diff --git a/include/linux/bootmem.h b/include/linux/bootmem.h index ab344a5..001c248 100644 --- a/include/linux/bootmem.h +++ b/include/linux/bootmem.h @@ -135,9 +135,6 @@ extern void *__alloc_bootmem_low_node(pg_data_t *pgdat, extern int reserve_bootmem_generic(unsigned long addr, unsigned long size, int flags); -extern void *alloc_bootmem_section(unsigned long size, - unsigned long section_nr); - #ifdef CONFIG_HAVE_ARCH_ALLOC_REMAP extern void *alloc_remap(int nid, unsigned long size); #else diff --git a/mm/bootmem.c b/mm/bootmem.c index 7bc0557..d34026c 100644 --- a/mm/bootmem.c +++ b/mm/bootmem.c @@ -756,32 +756,6 @@ void * __init __alloc_bootmem_node_high(pg_data_t *pgdat, unsigned long size, } -#ifdef CONFIG_SPARSEMEM -/** - * alloc_bootmem_section - allocate boot memory from a specific section - * @size: size of the request in bytes - * @section_nr: sparse map section to allocate from - * - * Return NULL on failure. - */ -void * __init alloc_bootmem_section(unsigned long size, - unsigned long section_nr) -{ - bootmem_data_t *bdata; - unsigned long pfn, goal, limit; - - pfn = section_nr_to_pfn(section_nr); - goal = pfn << PAGE_SHIFT; - if (size > BYTES_PER_SECTION) - limit = 0; - else - limit = section_nr_to_pfn(section_nr + 1) << PAGE_SHIFT; - bdata = &bootmem_node_data[early_pfn_to_nid(pfn)]; - - return alloc_bootmem_core(bdata, size, SMP_CACHE_BYTES, goal, limit); -} -#endif - void * __init __alloc_bootmem_node_nopanic(pg_data_t *pgdat, unsigned long size, unsigned long align, unsigned long goal) { diff --git a/mm/sparse.c b/mm/sparse.c index 9e032dc..ac0d5a3 100644 --- a/mm/sparse.c +++ b/mm/sparse.c @@ -273,10 +273,10 @@ static unsigned long *__kmalloc_section_usemap(void) #ifdef CONFIG_MEMORY_HOTREMOVE static unsigned long * __init sparse_early_usemaps_alloc_pgdat_section(struct pglist_data *pgdat, - unsigned long count) + unsigned long size) { - unsigned long section_nr; - + pg_data_t *host_pgdat; + unsigned long goal; /* * A page may contain usemaps for other sections preventing the * page being freed and making a section unremovable while @@ -287,8 +287,9 @@ sparse_early_usemaps_alloc_pgdat_section(struct pglist_data *pgdat, * from the same section as the pgdat where possible to avoid * this problem. */ - section_nr = pfn_to_section_nr(__pa(pgdat) >> PAGE_SHIFT); - return alloc_bootmem_section(usemap_size() * count, section_nr); + goal = __pa(pgdat) & PAGE_SECTION_MASK; + host_pgdat = NODE_DATA(early_pfn_to_nid(goal)); + return __alloc_bootmem_node(host_pgdat, size, SMP_CACHE_BYTES, goal); } static void __init check_usemap_section_nr(int nid, unsigned long *usemap) @@ -332,9 +333,9 @@ static void __init check_usemap_section_nr(int nid, unsigned long *usemap) #else static unsigned long * __init sparse_early_usemaps_alloc_pgdat_section(struct pglist_data *pgdat, - unsigned long count) + unsigned long size) { - return NULL; + return alloc_bootmem_node(pgdat, size); } static void __init check_usemap_section_nr(int nid, unsigned long *usemap) @@ -352,19 +353,7 @@ static void __init sparse_early_usemaps_alloc_node(unsigned long**usemap_map, int size = usemap_size(); usemap = sparse_early_usemaps_alloc_pgdat_section(NODE_DATA(nodeid), - usemap_count); - if (usemap) { - for (pnum = pnum_begin; pnum < pnum_end; pnum++) { - if (!present_section_nr(pnum)) - continue; - usemap_map[pnum] = usemap; - usemap += size; - check_usemap_section_nr(nodeid, usemap_map[pnum]); - } - return; - } - - usemap = alloc_bootmem_node(NODE_DATA(nodeid), size * usemap_count); + size * usemap_count); if (usemap) { for (pnum = pnum_begin; pnum < pnum_end; pnum++) { if (!present_section_nr(pnum))