Thomas Monjalon <tho...@monjalon.net> writes: > 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.
Ahh, okay. Yep, I agree with all you've written above.