Re: [PATCH 0/2] optimise iov_iter

[Pavel Begunkov]

On 19/11/2020 17:20, Jens Axboe wrote:
> On 11/19/20 10:14 AM, Pavel Begunkov wrote:
>> On 19/11/2020 16:46, Jens Axboe wrote:
>>> On 11/19/20 8:29 AM, Pavel Begunkov wrote:
>>>> The first patch optimises iov_iter_npages() for the bvec case, and the
>>>> second helps code generation to kill unreachable code.
>>>>
>>>> Pavel Begunkov (2):
>>>>   iov_iter: optimise iov_iter_npages for bvec
>>>>   iov_iter: optimise iter type checking
>>>>
>>>>  include/linux/uio.h | 10 +++++-----
>>>>  lib/iov_iter.c      | 10 +++++-----
>>>>  2 files changed, 10 insertions(+), 10 deletions(-)
>>>
>>> Nice! Tested this and confirmed both the better code generation,
>>> and reduction in overhead in iov_iter_npages().
>>
>> Thanks! Did you find t-put/etc. boost with your setup?
> 
> Yeah, for this kind of test, if we shave 1% off the stack overhead,
> that directly yields an increase in peak IOPS. My numbers were close
> to yours, dropped about 1% of system overhead.

That's great. I was guessing how much of it can be due
to not cached bvec and was just tossed to somewhere else.

-- 
Pavel Begunkov