[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH 0/4] Implement persistent grant in xen-netfront/netback
Hello, On Thu, Nov 15, 2012 at 03:03:07PM +0800, Annie Li wrote: > This patch implements persistent grants for xen-netfront/netback. This > mechanism maintains page pools in netback/netfront, these page pools is used > to > save grant pages which are mapped. This way improve performance which is > wasted > when doing grant operations. > > Current netback/netfront does map/unmap grant operations frequently when > transmitting/receiving packets, and grant operations costs much cpu clock. In > this patch, netfront/netback maps grant pages when needed and then saves them > into a page pool for future use. All these pages will be unmapped when > removing/releasing the net device. > Do you have performance numbers available already? with/without persistent grants? > In netfront, two pools are maintained for transmitting and receiving packets. > When new grant pages are needed, the driver gets grant pages from this pool > first. If no free grant page exists, it allocates new page, maps it and then > saves it into the pool. The pool size for transmit/receive is exactly tx/rx > ring size. The driver uses memcpy(not grantcopy) to copy data grant pages. > Here, memcpy is copying the whole page size data. I tried to copy len size > data > from offset, but network does not seem work well. I am trying to find the root > cause now. > > In netback, it also maintains two page pools for tx/rx. When netback gets a > request, it does a search first to find out whether the grant reference of > this request is already mapped into its page pool. If the grant ref is mapped, > the address of this mapped page is gotten and memcpy is used to copy data > between grant pages. However, if the grant ref is not mapped, a new page is > allocated, mapped with this grant ref, and then saved into page pool for > future use. Similarly, memcpy replaces grant copy to copy data between grant > pages. In this implementation, two arrays(gnttab_tx_vif,gnttab_rx_vif) are > used to save vif pointer for every request because current netback is not > per-vif based. This would be changed after implementing 1:1 model in netback. > Btw is xen-netback/xen-netfront multiqueue support something you're planning to implement aswell? multiqueue allows single vif scaling to multiple vcpus/cores. Thanks, -- Pasi > This patch supports both persistent-grant and non persistent grant. A new > xenstore key "feature-persistent-grants" is used to represent this feature. > > This patch is based on linux3.4-rc3. I hit netperf/netserver failure on > linux latest version v3.7-rc1, v3.7-rc2 and v3.7-rc4. Not sure whether this > netperf/netserver failure connects compound page commit in v3.7-rc1, but I did > hit BUG_ON with debug patch from thread > http://lists.xen.org/archives/html/xen-devel/2012-10/msg00893.html > > > Annie Li (4): > xen/netback: implements persistent grant with one page pool. > xen/netback: Split one page pool into two(tx/rx) page pool. > Xen/netfront: Implement persistent grant in netfront. > fix code indent issue in xen-netfront. > > drivers/net/xen-netback/common.h | 24 ++- > drivers/net/xen-netback/interface.c | 26 +++ > drivers/net/xen-netback/netback.c | 215 ++++++++++++++++++-- > drivers/net/xen-netback/xenbus.c | 14 ++- > drivers/net/xen-netfront.c | 378 > +++++++++++++++++++++++++++++------ > 5 files changed, 570 insertions(+), 87 deletions(-) > > -- > 1.7.3.4 > > > _______________________________________________ > Xen-devel mailing list > Xen-devel@xxxxxxxxxxxxx > http://lists.xen.org/xen-devel _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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