On 15/12/2020 04:41, Eric Biggers wrote: > On Mon, Dec 14, 2020 at 10:28:19AM +0800, Tony W Wang-oc wrote: >> On 12/12/2020 01:43, Eric Biggers wrote: >>> On Fri, Dec 11, 2020 at 07:29:04PM +0800, Tony W Wang-oc wrote: >>>> The driver crc32c-intel match CPUs supporting X86_FEATURE_XMM4_2. >>>> On platforms with Zhaoxin CPUs supporting this X86 feature, When >>>> crc32c-intel and crc32c-generic are both registered, system will >>>> use crc32c-intel because its .cra_priority is greater than >>>> crc32c-generic. This case expect to use crc32c-generic driver for >>>> some Zhaoxin CPUs to get performance gain, So remove these Zhaoxin >>>> CPUs support from crc32c-intel. >>>> >>>> Signed-off-by: Tony W Wang-oc <TonyWWang-oc@xxxxxxxxxxx> >>> >>> Does this mean that the performance of the crc32c instruction on those CPUs is >>> actually slower than a regular C implementation? That's very weird. >>> >> >> From the lmbench3 Create and Delete file test on those chips, I think yes. >> > > Did you try measuring the performance of the hashing itself, and not some > higher-level filesystem operations? > Yes. Was testing on these Zhaoxin CPUs, the result is that with the same input value the generic C implementation takes fewer time than the crc32c instruction implementation. Sincerely Tony
