On Thu, Oct 11, 2018 at 6:05 PM Vlastimil Babka <vba...@suse.cz> wrote: > > On 10/10/18 6:56 PM, Arun KS wrote: > > On 2018-10-10 21:00, Vlastimil Babka wrote: > >> On 10/5/18 10:10 AM, Arun KS wrote: > >>> When free pages are done with higher order, time spend on > >>> coalescing pages by buddy allocator can be reduced. With > >>> section size of 256MB, hot add latency of a single section > >>> shows improvement from 50-60 ms to less than 1 ms, hence > >>> improving the hot add latency by 60%. Modify external > >>> providers of online callback to align with the change. > >>> > >>> Signed-off-by: Arun KS <aru...@codeaurora.org> > >> > >> [...] > >> > >>> @@ -655,26 +655,44 @@ void __online_page_free(struct page *page) > >>> } > >>> EXPORT_SYMBOL_GPL(__online_page_free); > >>> > >>> -static void generic_online_page(struct page *page) > >>> +static int generic_online_page(struct page *page, unsigned int order) > >>> { > >>> - __online_page_set_limits(page); > >> > >> This is now not called anymore, although the xen/hv variants still do > >> it. The function seems empty these days, maybe remove it as a followup > >> cleanup? > >> > >>> - __online_page_increment_counters(page); > >>> - __online_page_free(page); > >>> + __free_pages_core(page, order); > >>> + totalram_pages += (1UL << order); > >>> +#ifdef CONFIG_HIGHMEM > >>> + if (PageHighMem(page)) > >>> + totalhigh_pages += (1UL << order); > >>> +#endif > >> > >> __online_page_increment_counters() would have used > >> adjust_managed_page_count() which would do the changes under > >> managed_page_count_lock. Are we safe without the lock? If yes, there > >> should perhaps be a comment explaining why. > > > > Looks unsafe without managed_page_count_lock. I think better have a > > similar implementation of free_boot_core() in memory_hotplug.c like we > > had in version 1 of patch. And use adjust_managed_page_count() instead > > of page_zone(page)->managed_pages += nr_pages; > > > > https://lore.kernel.org/patchwork/patch/989445/ > > Looks like deferred_free_range() has the same problem calling > __free_pages_core() to adjust zone->managed_pages. I expect > __free_pages_bootmem() is OK because at that point the system is still > single-threaded? > Could be solved by moving that out of __free_pages_core(). >
Seems deferred_free_range() is protected by pgdat_resize_lock()/pgdat_resize_unlock(). Which protects pgdat's zones, if I am right. > But do we care about readers potentially seeing a store tear? If yes > then maybe these counters should be converted to atomics... > > > -static void generic_online_page(struct page *page) > > +static int generic_online_page(struct page *page, unsigned int order) > > { > > - __online_page_set_limits(page); > > - __online_page_increment_counters(page); > > - __online_page_free(page); > > + unsigned long nr_pages = 1 << order; > > + struct page *p = page; > > + > > + for (loop = 0 ; loop < nr_pages ; loop++, p++) { > > + __ClearPageReserved(p); > > + set_page_count(p, 0); > > + } > > + > > + adjust_managed_page_count(page, nr_pages); > > + set_page_refcounted(page); > > + __free_pages(page, order); > > + > > + return 0; > > +} > > > > > > Regards, > > Arun > > > _______________________________________________ devel mailing list de...@linuxdriverproject.org http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel