On Thu 11-10-18 07:59:32, Arun KS wrote: > On 2018-10-10 23:03, Michal Hocko wrote: > > On Wed 10-10-18 22:26:41, 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 <arunks@xxxxxxxxxxxxxx> > > > > > > > > [...] > > > > > > > > > @@ -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. > > > > Why does it matter actually? We cannot online/offline memory in > > parallel. This is not the case for the boot where we initialize memory > > in parallel on multiple nodes. So this seems to be safe currently unless > > I am missing something. A comment explaining that would be helpful > > though. > > Other main callers of adjust_manage_page_count(), > > static inline void free_reserved_page(struct page *page) > { > __free_reserved_page(page); > adjust_managed_page_count(page, 1); > } > > static inline void mark_page_reserved(struct page *page) > { > SetPageReserved(page); > adjust_managed_page_count(page, -1); > } > > Won't they race with memory hotplug? > > Few more, > ./drivers/xen/balloon.c:519: adjust_managed_page_count(page, -1); > ./drivers/virtio/virtio_balloon.c:175: adjust_managed_page_count(page, -1); > ./drivers/virtio/virtio_balloon.c:196: adjust_managed_page_count(page, 1); > ./mm/hugetlb.c:2158: adjust_managed_page_count(page, 1 << > h->order); They can, and I have missed those. -- Michal Hocko SUSE Labs _______________________________________________ devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxx http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel