On Thu 28-02-13 15:10:25, Andrew Morton wrote: [...] > From: David Rientjes <[email protected]> > Subject: mm, show_mem: suppress page counts in non-blockable contexts > > On large systems with a lot of memory, walking all RAM to determine page > types may take a half second or even more. > > In non-blockable contexts, the page allocator will emit a page allocation > failure warning unless __GFP_NOWARN is specified. In such contexts, irqs > are typically disabled and such a lengthy delay may result in soft > lockups.
I have already asked about it in the original thread but didn't get any answer. How can we get a soft lockup when all implementations of show_mem call touch_nmi_watchdog? I do agree with the change but the above justification seems misleading. Can we just remove the information because it is costly and doesn't give us anything relevant to debug allocation failures? > To fix this, suppress the page walk in such contexts when printing the > page allocation failure warning. > > Signed-off-by: David Rientjes <[email protected]> > Cc: Mel Gorman <[email protected]> > Cc: Michal Hocko <[email protected]> > Cc: Dave Hansen <[email protected]> > Signed-off-by: Andrew Morton <[email protected]> > --- > > arch/arm/mm/init.c | 3 +++ > arch/ia64/mm/contig.c | 2 ++ > arch/ia64/mm/discontig.c | 2 ++ > arch/parisc/mm/init.c | 2 ++ > arch/unicore32/mm/init.c | 3 +++ > include/linux/mm.h | 3 ++- > lib/show_mem.c | 3 +++ > mm/page_alloc.c | 7 +++++++ > 8 files changed, 24 insertions(+), 1 deletion(-) > > diff -puN > arch/arm/mm/init.c~mm-show_mem-suppress-page-counts-in-non-blockable-contexts > arch/arm/mm/init.c > --- > a/arch/arm/mm/init.c~mm-show_mem-suppress-page-counts-in-non-blockable-contexts > +++ a/arch/arm/mm/init.c > @@ -99,6 +99,9 @@ void show_mem(unsigned int filter) > printk("Mem-info:\n"); > show_free_areas(filter); > > + if (filter & SHOW_MEM_FILTER_PAGE_COUNT) > + return; > + > for_each_bank (i, mi) { > struct membank *bank = &mi->bank[i]; > unsigned int pfn1, pfn2; > diff -puN > arch/ia64/mm/contig.c~mm-show_mem-suppress-page-counts-in-non-blockable-contexts > arch/ia64/mm/contig.c > --- > a/arch/ia64/mm/contig.c~mm-show_mem-suppress-page-counts-in-non-blockable-contexts > +++ a/arch/ia64/mm/contig.c > @@ -47,6 +47,8 @@ void show_mem(unsigned int filter) > printk(KERN_INFO "Mem-info:\n"); > show_free_areas(filter); > printk(KERN_INFO "Node memory in pages:\n"); > + if (filter & SHOW_MEM_FILTER_PAGE_COUNT) > + return; > for_each_online_pgdat(pgdat) { > unsigned long present; > unsigned long flags; > diff -puN > arch/ia64/mm/discontig.c~mm-show_mem-suppress-page-counts-in-non-blockable-contexts > arch/ia64/mm/discontig.c > --- > a/arch/ia64/mm/discontig.c~mm-show_mem-suppress-page-counts-in-non-blockable-contexts > +++ a/arch/ia64/mm/discontig.c > @@ -623,6 +623,8 @@ void show_mem(unsigned int filter) > > printk(KERN_INFO "Mem-info:\n"); > show_free_areas(filter); > + if (filter & SHOW_MEM_FILTER_PAGE_COUNT) > + return; > printk(KERN_INFO "Node memory in pages:\n"); > for_each_online_pgdat(pgdat) { > unsigned long present; > diff -puN > arch/parisc/mm/init.c~mm-show_mem-suppress-page-counts-in-non-blockable-contexts > arch/parisc/mm/init.c > --- > a/arch/parisc/mm/init.c~mm-show_mem-suppress-page-counts-in-non-blockable-contexts > +++ a/arch/parisc/mm/init.c > @@ -697,6 +697,8 @@ void show_mem(unsigned int filter) > > printk(KERN_INFO "Mem-info:\n"); > show_free_areas(filter); > + if (filter & SHOW_MEM_FILTER_PAGE_COUNT) > + return; > #ifndef CONFIG_DISCONTIGMEM > i = max_mapnr; > while (i-- > 0) { > diff -puN > arch/unicore32/mm/init.c~mm-show_mem-suppress-page-counts-in-non-blockable-contexts > arch/unicore32/mm/init.c > --- > a/arch/unicore32/mm/init.c~mm-show_mem-suppress-page-counts-in-non-blockable-contexts > +++ a/arch/unicore32/mm/init.c > @@ -66,6 +66,9 @@ void show_mem(unsigned int filter) > printk(KERN_DEFAULT "Mem-info:\n"); > show_free_areas(filter); > > + if (filter & SHOW_MEM_FILTER_PAGE_COUNT) > + return; > + > for_each_bank(i, mi) { > struct membank *bank = &mi->bank[i]; > unsigned int pfn1, pfn2; > diff -puN > include/linux/mm.h~mm-show_mem-suppress-page-counts-in-non-blockable-contexts > include/linux/mm.h > --- > a/include/linux/mm.h~mm-show_mem-suppress-page-counts-in-non-blockable-contexts > +++ a/include/linux/mm.h > @@ -900,7 +900,8 @@ extern void pagefault_out_of_memory(void > * Flags passed to show_mem() and show_free_areas() to suppress output in > * various contexts. > */ > -#define SHOW_MEM_FILTER_NODES (0x0001u) /* filter disallowed > nodes */ > +#define SHOW_MEM_FILTER_NODES (0x0001u) /* disallowed > nodes */ > +#define SHOW_MEM_FILTER_PAGE_COUNT (0x0002u) /* page type count */ > > extern void show_free_areas(unsigned int flags); > extern bool skip_free_areas_node(unsigned int flags, int nid); > diff -puN > lib/show_mem.c~mm-show_mem-suppress-page-counts-in-non-blockable-contexts > lib/show_mem.c > --- > a/lib/show_mem.c~mm-show_mem-suppress-page-counts-in-non-blockable-contexts > +++ a/lib/show_mem.c > @@ -18,6 +18,9 @@ void show_mem(unsigned int filter) > printk("Mem-Info:\n"); > show_free_areas(filter); > > + if (filter & SHOW_MEM_FILTER_PAGE_COUNT) > + return; > + > for_each_online_pgdat(pgdat) { > unsigned long i, flags; > > diff -puN > mm/page_alloc.c~mm-show_mem-suppress-page-counts-in-non-blockable-contexts > mm/page_alloc.c > --- > a/mm/page_alloc.c~mm-show_mem-suppress-page-counts-in-non-blockable-contexts > +++ a/mm/page_alloc.c > @@ -2009,6 +2009,13 @@ void warn_alloc_failed(gfp_t gfp_mask, i > return; > > /* > + * Walking all memory to count page types is very expensive and should > + * be inhibited in non-blockable contexts. > + */ > + if (!(gfp_mask & __GFP_WAIT)) > + filter |= SHOW_MEM_FILTER_PAGE_COUNT; > + > + /* > * This documents exceptions given to allocations in certain > * contexts that are allowed to allocate outside current's set > * of allowed nodes. > _ > > Patches currently in -mm which might be from [email protected] are > > origin.patch > mm-show_mem-suppress-page-counts-in-non-blockable-contexts.patch > mm-dmapoolc-fix-null-dev-in-dma_pool_create.patch > -- Michal Hocko SUSE Labs -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
