Hi all- Here's v4 of the APST patch set. The biggest bikesheddable thing (I think) is the scaling factor. I currently have it hardcoded so that we wait 50x the total latency before entering a power saving state. On my Samsung 950, this means we enter state 3 (70mW, 0.5ms entry latency, 5ms exit latency) after 275ms and state 4 (5mW, 2ms entry latency, 22ms exit latency) after 1200ms. I have the default max latency set to 25ms.
FWIW, in practice, the latency this introduces seems to be well under 22ms, but my benchmark is a bit silly and I might have measured it wrong. I certainly haven't observed a slowdown just using my laptop. This time around, I changed the names of parameters after Jay Frayensee got confused by the first try. Now they are: - ps_max_latency_us in sysfs: actually controls it. - nvme_core.default_ps_max_latency_us: sets the default. Yeah, they're mouthfuls, but they should be clearer now. Changes from v3: - Remove const from nvme_set_feature()'s parameter. My inner C++ programmer cringes a little... Changes from v2: - Rename the parameters. Changes from v1: - Get rid of feature buffer alignment warnings. - Change the error message if NPSS is bogus. - Rename apst_max_latency_ns to apst_max_latency_us because module params don't like u64 or unsigned long long and I wanted to make it fit more comfortably in a ulong module param. (And the nanoseconds were useless.) - Add a module parameter for the default max latency. Andy Lutomirski (3): nvme/scsi: Remove power management support nvme: Pass pointers, not dma addresses, to nvme_get/set_features() nvme: Enable autonomous power state transitions drivers/nvme/host/core.c | 180 ++++++++++++++++++++++++++++++++++++++++++++--- drivers/nvme/host/nvme.h | 10 ++- drivers/nvme/host/scsi.c | 80 ++------------------- include/linux/nvme.h | 6 ++ 4 files changed, 192 insertions(+), 84 deletions(-) -- 2.7.4