diff options
| author | Kai-Heng Feng <kai.heng.feng@canonical.com> | 2017-06-07 15:25:42 +0800 |
|---|---|---|
| committer | Christoph Hellwig <hch@lst.de> | 2017-06-07 11:08:54 +0200 |
| commit | da87591bea92204fcb921bac927666eb7141908e (patch) | |
| tree | f23d1207718ee18218ce4267cbcb0f361456e818 | |
| parent | 24b7f0592f738a1127c72dbf5b72a83997dd6997 (diff) | |
nvme: only consider exit latency when choosing useful non-op power states
When a NVMe is in non-op states, the latency is exlat.
The latency will be enlat + exlat only when the NVMe tries to transit
from operational state right atfer it begins to transit to
non-operational state, which should be a rare case.
Therefore, as Andy Lutomirski suggests, use exlat only when deciding power
states to trainsit to.
Signed-off-by: Kai-Heng Feng <kai.heng.feng@canonical.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
| -rw-r--r-- | drivers/nvme/host/core.c | 15 |
1 files changed, 9 insertions, 6 deletions
diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c index 0f9cc0c55e15..c07d8d4e18c9 100644 --- a/drivers/nvme/host/core.c +++ b/drivers/nvme/host/core.c @@ -1342,7 +1342,7 @@ static void nvme_configure_apst(struct nvme_ctrl *ctrl) * transitioning between power states. Therefore, when running * in any given state, we will enter the next lower-power * non-operational state after waiting 50 * (enlat + exlat) - * microseconds, as long as that state's total latency is under + * microseconds, as long as that state's exit latency is under * the requested maximum latency. * * We will not autonomously enter any non-operational state for @@ -1387,7 +1387,7 @@ static void nvme_configure_apst(struct nvme_ctrl *ctrl) * lowest-power state, not the number of states. */ for (state = (int)ctrl->npss; state >= 0; state--) { - u64 total_latency_us, transition_ms; + u64 total_latency_us, exit_latency_us, transition_ms; if (target) table->entries[state] = target; @@ -1408,12 +1408,15 @@ static void nvme_configure_apst(struct nvme_ctrl *ctrl) NVME_PS_FLAGS_NON_OP_STATE)) continue; - total_latency_us = - (u64)le32_to_cpu(ctrl->psd[state].entry_lat) + - + le32_to_cpu(ctrl->psd[state].exit_lat); - if (total_latency_us > ctrl->ps_max_latency_us) + exit_latency_us = + (u64)le32_to_cpu(ctrl->psd[state].exit_lat); + if (exit_latency_us > ctrl->ps_max_latency_us) continue; + total_latency_us = + exit_latency_us + + le32_to_cpu(ctrl->psd[state].entry_lat); + /* * This state is good. Use it as the APST idle * target for higher power states. |