On 11/21/19 7:16 AM, Jackie Liu wrote: > 在 2019/11/21 21:47, Jens Axboe 写道: >> On 11/21/19 5:49 AM, Jackie Liu wrote: >>> >>> >>> On 2019/11/21 20:40, Pavel Begunkov wrote: >>>>> 在 2019/11/21 17:43, Pavel Begunkov 写道: >>>>>> On 11/21/2019 12:26 PM, Jackie Liu wrote: >>>>>>> 2019年11月21日 16:54，Pavel Begunkov <asml.silence@xxxxxxxxx> 写道： >>>>>>>> >>>>>>>> If there is a DRAIN in the middle of a link, it uses shadow req. Defer >>>>>>>> the next request/link instead. This: >>>>>>>> >>>>>>>> Pros: >>>>>>>> 1. removes semi-duplicated code >>>>>>>> 2. doesn't allocate memory for shadows >>>>>>>> 3. works better if only the head marked for drain >>>>>>> >>>>>>> I thought about this before, just only drain the head, but if the >>>>>>> latter IO depends >>>>>>> on the link-list, then latter IO will run in front of the link-list. >>>>>>> If we think it >>>>>>> is acceptable, then I think it is ok for me. >>>>>> >>>>>> If I got your point right, latter requests won't run ahead of the >>>>>> link-list. There shouldn't be change of behaviour. >>>>>> >>>>>> The purpose of shadow requests is to mark some request right ahead of >>>>>> the link for draining. This patch uses not a specially added shadow >>>>>> request, but the following regular one. And, as drained IO shouldn't be >>>>>> issued until every request behind completed, this should give the same >>>>>> effect. >>>>>> >>>>>> Am I missed something? >>>>> >>>>> Thanks for explaining. This is also correct, if I understand >>>>> correctly, It seems that other IOs will wait for all the links are >>>>> done. this is a little different, is it? >>>> >>>> Yes, you're right, it also was briefly stated in the patch description >>>> (see Cons). I hope, links + drain in the middle is an uncommon case. >>>> But it can be added back, but may become a little bit uglier. >>>> >>>> What do you think, should we care about this case? >>> >>> Yes, this is a very tiny scene. When I first time wrote this part of the >>> code, my suggestion was to ban it directly. >>> >>> For this patch, I am fine, Jens, what do you think. >> >> I am fine with it as well, it'd be nice to get rid of needing that >> extra request. >> >> Was that a reviewed-by from you? It'd be nice to get these more >> formally so I can add the attributes. I'll drop the other patch. > > I want to do more tests. There is no test machine at this time, at least > until tomorrow morning. OK, no worries, for the record I did run it through testing this morning and it passes for me. Before this (or my) patch, we'd stall pretty quickly in the link_drain tested if run repeatedly. >>> The mailing list always rejects my mail, is my smtp server IP banned? >> >> Probably because you have text/html in your email, the list is pretty >> picky when it comes to anything that isn't just text/plain. > > I don't know, I use thunderbird to write emails, and it has been set to > plain text, perhaps because of the signature, I have to check my mail > client. Feel free to try and send an email to me personally, then I can see what it looks like. -- Jens Axboe
