On Fri, 9 Feb 2018 14:22:16 -0500 Pavel Tatashin <pasha.tatashin@xxxxxxxxxx> wrote: > Deferred page initialization allows the boot cpu to initialize a small > subset of the system's pages early in boot, with other cpus doing the rest > later on. > > It is, however, problematic to know how many pages the kernel needs during > boot. Different modules and kernel parameters may change the requirement, > so the boot cpu either initializes too many pages or runs out of memory. > > To fix that, initialize early pages on demand. This ensures the kernel > does the minimum amount of work to initialize pages during boot and leaves > the rest to be divided in the multithreaded initialization path > (deferred_init_memmap). > > The on-demand code is permanently disabled using static branching once > deferred pages are initialized. After the static branch is changed to > false, the overhead is up-to two branch-always instructions if the zone > watermark check fails or if rmqueue fails. lgtm, I'll toss it in for some testing. A couple of tweaks: From: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Subject: mm-initialize-pages-on-demand-during-boot-fix fix typo in comment, make deferred_pages static Cc: Pavel Tatashin <pasha.tatashin@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/page_alloc.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff -puN include/linux/memblock.h~mm-initialize-pages-on-demand-during-boot-fix include/linux/memblock.h diff -puN mm/memblock.c~mm-initialize-pages-on-demand-during-boot-fix mm/memblock.c diff -puN mm/page_alloc.c~mm-initialize-pages-on-demand-during-boot-fix mm/page_alloc.c --- a/mm/page_alloc.c~mm-initialize-pages-on-demand-during-boot-fix +++ a/mm/page_alloc.c @@ -1568,14 +1568,14 @@ static int __init deferred_init_memmap(v } /* - * This lock grantees that only one thread at a time is allowed to grow zones + * This lock guarantees that only one thread at a time is allowed to grow zones * (decrease number of deferred pages). * Protects first_deferred_pfn field in all zones during early boot before * deferred pages are initialized. Deferred pages are initialized in * page_alloc_init_late() soon after smp_init() is complete. */ static __initdata DEFINE_SPINLOCK(deferred_zone_grow_lock); -DEFINE_STATIC_KEY_TRUE(deferred_pages); +static DEFINE_STATIC_KEY_TRUE(deferred_pages); /* * If this zone has deferred pages, try to grow it by initializing enough _ -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
