Re: Question about sendfile

[Hao Xu <haoxu@linux.alibaba.com>]

在 2021/7/7 下午10:16, Pavel Begunkov 写道:
> On 7/3/21 11:47 AM, Hao Xu wrote:
>> Hi Pavel,
>> I found this mail about sendfile in the maillist, may I ask why it's not
>> good to have one pipe each for a io-wq thread.
>> https://lore.kernel.org/io-uring/94dbbb15-4751-d03c-01fd-d25a0fe98e25@gmail.com/
> 
> IIRC, it's one page allocated for each such task, which is bearable but
> don't like yet another chunk of uncontrollable implicit state. If there
> not a bunch of active workers, IFAIK there is no way to force them to
> drop their pipes.
> 
> I also don't remember the restrictions on the sendfile and what's with
> the eternal question of "what to do if the write part of sendfile has
> failed".
I haven't dig into it deeply, will do some investigation.
> 
> Though, workers are now much more alike to user threads, so there
> should be less of concern. And even though my gut feeling don't like
> them, it may actually be useful. Do you have a good use case where
> explicit pipes don't work well?
The thing is two linked splice sqes may be cut off in shared sqthread
case.
>