Please review this patch
Problem ------- We are using an ARM embedded platform and require 16KiB NTB's to allow for fast data transfer. Unfortunately we have found that there are times after running the kernel for a while and transferring a lot of data over the CDC-NCM connection that it can become harder to find 16KiB pages of memory for allocation. This results in a disconnection of the NCM Gadget attached to the host platform. We are running with reduced buffers to not cross over into the 32KiB page boundary by setting the buffer sizes to: tx_max=16000 rx_max=16000 Analysis -------- We identified through investigation that the lack of 16KiB pages would be short lived as the kernel would compact the buddy list soon after the failure which results in pages being available within seconds. Solution -------- In order to avoid disconnections I implemented a patch that will attempt to use a 2048 Byte minimum size NTB if the allocation of the maximum size NTB fails. This allows the connection to limp along until the memory has been recovered which was usually between 1 and 4 NTBS on our heavy traffic system. Jim Baxter (1): net: cdc_ncm: Reduce memory use when kernel memory low drivers/net/usb/cdc_ncm.c | 39 +++++++++++++++++++++++++++------------ include/linux/usb/cdc_ncm.h | 1 + 2 files changed, 28 insertions(+), 12 deletions(-) -- 1.9.1
