On Fri, Mar 20, 2020 at 6:27 AM John Hubbard <jhubbard@xxxxxxxxxx> wrote: > > On 3/15/20 9:34 PM, Pingfan Liu wrote: > > Introduce a PIN_FAST_LONGTERM_BENCHMARK ioctl to test longterm pin in gup fast > > path. > > 1. The subject line still has "benchemark", which should be "benchmark". > > 2. What do you really want to test? More about the use case to be tested would help. > Just another sentence. I wouldn't normally ask, but in this case the implementation > is slightly scrambled, and I can't suggest how to fix it because there's no information > in the commit log as to the use case, nor the motivation. Oh, the history about [3/3] is to verify the implementation method of [2/3]. Please refer to https://lore.kernel.org/linux-mm/20190611122935.GA9919@xxxxxxxxxxxxxxxxxxxxxxxxxx/ Cite " > > I think the concern is: for the successful gup_fast case with no CMA > > pages, this patch is adding another complete loop through all the > > pages. In the fast case. > > > > If the check were instead done as part of the gup_pte_range(), then > > it would be a little more efficient for that case. > > > > As for whether it's worth it, *probably* this is too small an effect to measure. > > But in order to attempt a measurement: running fio (https://github.com/axboe/fio) > > with O_DIRECT on an NVMe drive, might shed some light. Here's an fio.conf file > > that Jan Kara and Tom Talpey helped me come up with, for related testing: " But I think now, there is no motivation for it, and can be dropped it now. Thanks, Pingfan
