On Mon, Mar 04, 2013 at 02:14:02AM +0000, KY Srinivasan wrote: > > > > -----Original Message----- > > From: Greg KH [mailto:gregkh@xxxxxxxxxxxxxxxxxxx] > > Sent: Sunday, March 03, 2013 9:08 PM > > To: KY Srinivasan > > Cc: linux-kernel@xxxxxxxxxxxxxxx; devel@xxxxxxxxxxxxxxxxxxxxxx; olaf@xxxxxxxxx; > > apw@xxxxxxxxxxxxx; andi@xxxxxxxxxxxxxx; akpm@xxxxxxxxxxxxxxxxxxxx; linux- > > mm@xxxxxxxxx > > Subject: Re: [PATCH 1/1] mm: Export split_page(). > > > > On Sun, Mar 03, 2013 at 06:27:55PM -0800, K. Y. Srinivasan wrote: > > > The split_page() function will be very useful for balloon drivers. On Hyper-V, > > > it will be very efficient to use 2M allocations in the guest as this (a) makes > > > the ballooning protocol with the host that much more efficient and (b) moving > > > memory in 2M chunks minimizes fragmentation in the host. Export the > > split_page() > > > function to let the guest allocations be in 2M chunks while the host is free to > > > return this memory at arbitrary granularity. > > > > > > > > > Signed-off-by: K. Y. Srinivasan <kys@xxxxxxxxxxxxx> > > > --- > > > mm/page_alloc.c | 1 + > > > 1 files changed, 1 insertions(+), 0 deletions(-) > > > > > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > > > index 6cacfee..7e0ead6 100644 > > > --- a/mm/page_alloc.c > > > +++ b/mm/page_alloc.c > > > @@ -1404,6 +1404,7 @@ void split_page(struct page *page, unsigned int order) > > > for (i = 1; i < (1 << order); i++) > > > set_page_refcounted(page + i); > > > } > > > +EXPORT_SYMBOL_GPL(split_page); > > > > When you export a symbol, you also need to post the code that is going > > to use that symbol, otherwise people don't really know how to judge this > > request. > > > > Can you just make this a part of your balloon driver update patch series > > instead? > > Fair enough; I was hoping to see how inclined the mm folks were with regards to > exporting this symbol before I went ahead and modified the balloon driver code to > leverage this. Looking at the Windows guests on Hyper-V, I am convinced 2M balloon > allocations in the Linux (Hyper-V) balloon driver will make significant difference. As you > suggest, I will post this patch as part of the balloon driver changes that use this exported > symbol. I am still hoping to get some feedback from the mm guys on this. I guess the most obvious question about exporting this symbol is, "Why doesn't any of the other hypervisor balloon drivers need this? What is so special about hyper-v?" Or can those other drivers also need/use it as well, and they were just too chicken to be asking for the export? :) thanks, greg k-h -- 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>