[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] [PATCH 0/4] Implement persistent grant in xen-netfront/netback
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. 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. 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
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