David Laight <david.lai...@aculab.com> 于2020年12月23日周三 上午2:42写道： > > From: qianjun > > Sent: 22 December 2020 12:19 > > > > In our project, Many business delays come from fork, so > > we started looking for the reason why fork is time-consuming. > > I used the ftrace with function_graph to trace the fork, found > > that the vm_normal_page will be called tens of thousands and > > the execution time of this vm_normal_page function is only a > > few nanoseconds. And the vm_normal_page is not a inline function. > > So I think if the function is inline style, it maybe reduce the > > call time overhead. > > Beware of taking timings from ftrace function trace. > The cost of the tracing is significant. > > You can get sensible numbers if you only trace very specific > functions. > Slightly annoyingly the output format changes if you enable > the function exit trace - useful for the timestamp. > ISTR it is possible to get the process id traced if you fiddle > with enough options. > > David >
Thanks for your time I have closed the ftrace when the test program is running. So the time diff is without the ftrace interference.And what does ISTR stand for :) thanks. > - > Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 > 1PT, UK > Registration No: 1397386 (Wales) >
