Hi Arnd, On 01/29/2016 03:22 PM, Arnd Bergmann wrote: > > For the ACPI case, I still think that an AML call from the AHCI driver > is the most logical solution. You mentioned that you believe that calling > into the AML interpreter up to 100 times per second is a noticeable > overhead, but I doubt that and would like to see actual number backing > that up. Note that most of the time, the status of the LEDs won't even > change, so the driver does not have to call into the AML while I/O > is in progress, or while it is stopped, only for the transition or in > case of locate and fault events that should be extremely rare. > During disk activity ahci_sw_activity_blink() is called based on timer expiration (~100ms). I just enabled the function profiler for 'dd if=/dev/zero of=/root/tmp bs=1M count=4096' and see the output below. The function was called 37 times in 2.5s #echo 1 > function_profile_enabled
#dd if=/dev/zero of=/root/tempfile bs=1M count=4096 4096+0 records in 4096+0 records out 4294967296 bytes (4.3 GB) copied, 2.57334 s, 1.7 GB/s #echo 0 > function_profile_enabled #cat trace_stat/* Function Hit Time Avg s^2 -------- --- ---- --- --- seattle_transmit_led_message 37 25.088 us 0.678 us 0.050 us I am not debating on your AML call recommendation, it sounds like a good idea however BIOS is already released hence its bit late to add AML methods for this. I am seeking guidance on what can be done in the given situation. I thought platform driver is one option to get this feature enabled in kernel. - Brijesh > Arnd >
