mm, x86, pat: Improve scaling of pat_pagerange_is_ram()
PATCH 1/1 mm, x86, pat: Improve scaling of pat_pagerange_is_ram()
Function pat_pagerange_is_ram() scales poorly to large address ranges, because it probes the resource tree for each page. On a 2.6 GHz Opteron, this function consumes 34 ms. for a 1 GB range. It is called twice during untrack_pfn_vma(), slowing process cleanup and handicapping the OOM killer.
This replacement based on walk_system_ram_range() consumes less than 1 ms. under the same conditions.
Signed-off-by John Dykstra <[email protected]> on behalf of Cray Inc.
Cc Suresh Siddha <[email protected]>
--- arch/x86/mm/pat.c | 55 ++++++++++++++++++++++++++++++----------------- include/linux/ioport.h | 2 + kernel/resource.c | 2 +- 3 files changed, 38 insertions(+), 21 deletions(-)
arch/x86/mm/pat.c +33 -18
@@ -160,29 +160,44 @@ static unsigned long pat_x_mtrr_type(u64 start, u64 end, unsigned long req_type)static int pat_pagerange_is_ram (resource_size_t start,resource_size_t end) { -int ram_page =0 , not_rampage =0 ; -unsigned long page_nr; +struct resource res; +resource_size_t pg_end, after_ram; +int ram =0 , not_ram =0 ; -for (page_nr = (start >>PAGE_SHIFT ); page_nr < (end >>PAGE_SHIFT ); - ++page_nr) { -/* -* For legacy reasons, physical address range in the legacy ISA -* region is tracked as non-RAM. This will allow users of -* /dev/mem to map portions of legacy ISA region, even when -* some of those portions are listed(or not even listed) with -* different e820 types(RAM/reserved/..) -*/ -if (page_nr >= (ISA_END_ADDRESS >>PAGE_SHIFT ) && -page_is_ram (page_nr)) - ram_page =1 ; -else - not_rampage =1 ; + res.start = start &PHYSICAL_PAGE_MASK ; -if (ram_page == not_rampage) +/* +* For legacy reasons, physical address range in the legacy ISA +* region is tracked as non-RAM. This will allow users of +* /dev/mem to map portions of legacy ISA region, even when +* some of those portions are listed(or not even listed) with +* different e820 types(RAM/reserved/..) +*/ +if (res.start <ISA_END_ADDRESS ) { + not_ram =1 ; + res.start =ISA_END_ADDRESS ; + } + + pg_end = (end +PAGE_SIZE -1 ) &PHYSICAL_PAGE_MASK ; + res.end = pg_end; + res.flags =IORESOURCE_MEM |IORESOURCE_BUSY ; + after_ram = res.start; +while ((res.start < res.end) && + (find_next_system_ram (&res,"System RAM" ) >=0 )) { +if (res.start > after_ram) + not_ram =1 ; +if (res.end > res.start) + ram =1 ; + +if (ram && not_ram)return -1 ; + + after_ram = res.end +1 ; + res.start = res.end +1 ; + res.end = pg_end; } -return ram_page; +return ram; }/*
include/linux/ioport.h +2 -0
@@ -223,5 +223,7 @@ extern int walk_system_ram_range(unsigned long start_pfn, unsigned long nr_pages, void *arg, int (*func)(unsigned long, unsigned long, void *)); +extern int find_next_system_ram (struct resource *res,char *name); +#endif /* __ASSEMBLY__ */ #endif /* _LINUX_IOPORT_H */
kernel/resource.c +1 -1
@@ -283,7 +283,7 @@ EXPORT_SYMBOL(release_resource);* the caller must specify res->start, res->end, res->flags and "name". * If found, returns 0, res is overwritten, if not found, returns -1. */ -static int find_next_system_ram (struct resource *res,char *name) +int find_next_system_ram (struct resource *res,char *name) {resource_size_t start, end;struct resource *p;
Signature · 1 line
1.7.0.4