On 27/09/18 08:58, 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> > --- > Changes since v2: > reuse code from __free_pages_boot_core() > > Changes since v1: > - Removed prefetch() > > Changes since RFC: > - Rebase. > - As suggested by Michal Hocko remove pages_per_block. > - Modifed external providers of online_page_callback. > > v2: https://lore.kernel.org/patchwork/patch/991363/ > v1: https://lore.kernel.org/patchwork/patch/989445/ > RFC: https://lore.kernel.org/patchwork/patch/984754/ > > --- > drivers/hv/hv_balloon.c | 6 ++++-- > drivers/xen/balloon.c | 18 ++++++++++++++--- > include/linux/memory_hotplug.h | 2 +- > mm/internal.h | 1 + > mm/memory_hotplug.c | 44 ++++++++++++++++++++++++++++++------------ > mm/page_alloc.c | 2 +- > 6 files changed, 54 insertions(+), 19 deletions(-) > ... > diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c > index e12bb25..010cf4d 100644 > --- a/drivers/xen/balloon.c > +++ b/drivers/xen/balloon.c > @@ -390,8 +390,8 @@ static enum bp_state reserve_additional_memory(void) > > /* > * add_memory_resource() will call online_pages() which in its turn > - * will call xen_online_page() callback causing deadlock if we don't > - * release balloon_mutex here. Unlocking here is safe because the > + * will call xen_bring_pgs_online() callback causing deadlock if we > + * don't release balloon_mutex here. Unlocking here is safe because the > * callers drop the mutex before trying again. > */ > mutex_unlock(&balloon_mutex); > @@ -422,6 +422,18 @@ static void xen_online_page(struct page *page) > mutex_unlock(&balloon_mutex); > } > > +static int xen_bring_pgs_online(struct page *pg, unsigned int order) > +{ > + unsigned long i, size = (1 << order); > + unsigned long start_pfn = page_to_pfn(pg); > + > + pr_debug("Online %lu pages starting at pfn 0x%lx\n", size, start_pfn); > + for (i = 0; i < size; i++) > + xen_online_page(pfn_to_page(start_pfn + i)); xen_online_page() isn't very complex and this is the only user. Why don't you move its body in here and drop the extra function? And now you can execute the loop with balloon_mutex held instead of taking and releasing it in each iteration of the loop. Juergen
