On 5/22/22 7:28 PM, Jens Axboe wrote:
> On 5/22/22 7:22 PM, Jens Axboe wrote:
>> On 5/22/22 6:42 PM, Al Viro wrote:
>>> On Sun, May 22, 2022 at 02:03:35PM -0600, Jens Axboe wrote:
>>>
>>>> Right, I'm saying it's not _immediately_ clear which cases are what when
>>>> reading the code.
>>>>
>>>>> up a while ago.  And no, turning that into indirect calls ended up with
>>>>> arseloads of overhead, more's the pity...
>>>>
>>>> It's a shame, since indirect calls make for nicer code, but it's always
>>>> been slower and these days even more so.
>>>>
>>>>> Anyway, at the moment I have something that builds; hadn't tried to
>>>>> boot it yet.
>>>>
>>>> Nice!
>>>
>>> Boots and survives LTP and xfstests...  Current variant is in
>>> vfs.git#work.iov_iter (head should be at 27fa77a9829c).  I have *not*
>>> looked into the code generation in primitives; the likely/unlikely on
>>> those cascades of ifs need rethinking.
>>
>> I noticed too. Haven't fiddled much in iov_iter.c, but for uio.h I had
>> the below. iov_iter.c is a worse "offender" though, with 53 unlikely and
>> 22 likely annotations...
> 
> Here it is...

Few more, most notably making sure that dio dirties reads even if they
are not of the iovec type.

Last two just add a helper for import_ubuf() and then adopts it for
io_uring send/recv which is also a hot path. The single range read/write
can be converted too, but that needs a bit more work...

-- 
Jens Axboe