Re: [PATCHSET 0/2] Turn single segment imports into ITER_UBUF

[Jens Axboe <axboe@kernel.dk>]

On 3/24/23 10:46 PM, Al Viro wrote:
> On Fri, Mar 24, 2023 at 02:44:41PM -0600, Jens Axboe wrote:
>> Hi,
>>
>> We've been doing a few conversions of ITER_IOVEC to ITER_UBUF in select
>> spots, as the latter is cheaper to iterate and hence saves some cycles.
>> I recently experimented [1] with io_uring converting single segment READV
>> and WRITEV into non-vectored variants, as we can save some cycles through
>> that as well.
>>
>> But there's really no reason why we can't just do this further down,
>> enabling it for everyone. It's quite common to use vectored reads or
>> writes even with a single segment, unfortunately, even for cases where
>> there's no specific reason to do so. From a bit of non-scientific
>> testing on a vm on my laptop, I see about 60% of the import_iovec()
>> calls being for a single segment.
>>
>> I initially was worried that we'd have callers assuming an ITER_IOVEC
>> iter after a call import_iovec() or import_single_range(), but an audit
>> of the kernel code actually looks sane in that regard. Of the ones that
>> do call it, I ran the ltp test cases and they all still pass.
> 
> Which tree was that audit on?  Mainline?  Some branch in block.git?

It was just master in -git. But looks like I did miss two spots, I've
updated the series here and will send out a v2:

https://git.kernel.dk/cgit/linux-block/log/?h=iter-ubuf

-- 
Jens Axboe