12/09/2017 22:29, Aaron Conole: > Thomas Monjalon <tho...@monjalon.net> writes: > > > 12/09/2017 16:50, Aaron Conole: > >> Eelco Chaudron <echau...@redhat.com> writes: > >> > >> > Call the mlockall() function, to attempt to lock all of its process > >> > memory into physical RAM, and preventing the kernel from paging any > >> > of its memory to disk. > >> > > >> > When using testpmd for performance testing, depending on the code path > >> > taken, we see a couple of page faults in a row. These faults effect > >> > the overall drop-rate of testpmd. On Linux the mlockall() call will > >> > prefault all the pages of testpmd (and the DPDK libraries if linked > >> > dynamically), even without LD_BIND_NOW. > >> > > >> > Signed-off-by: Eelco Chaudron <echau...@redhat.com> > >> > >> Acked-by: Aaron Conole <acon...@redhat.com> > > > > It is interesting, but why make it in testpmd? > > > > Maybe it should be documented in this guide: > > http://dpdk.org/doc/guides/linux_gsg/nic_perf_intel_platform.html > > Well, I'm not sure what the user would be able to do to get the > prefaulting performance without having a library they use with > LD_PRELOAD and a function with the constructor attribute which does the > same thing, AND export LD_BIND_NOW before linking starts. > > The LD_BIND_NOW simply does the symbol resolution, but there's no > guarantee that it will fault all the code pages in to process space, and > without an mlockall(), I'm not sure that there's any kind of guarantee > that they don't get swapped out of resident memory (which also leads to > later page faults). > > Maybe I misunderstood the question?
Maybe you misunderstood :) I was saying that if this improvement applies to applications, it should be documented in the tuning guide.
