On 01/06/2017 05:48 PM, Eric Dumazet wrote: > On Fri, Jan 6, 2017 at 8:31 AM, Vlastimil Babka <vba...@suse.cz> wrote: > >> >> I wonder what's that cause of the penalty (when accessing the vmapped >> area I suppose?) Is it higher risk of collisions cache misses within the >> area, compared to consecutive physical adresses? > > I believe tests were done with 48 fq qdisc, each having 2^16 slots. > So I had 48 blocs,of 524288 bytes. > > Trying a bit harder at setup time to get 128 consecutive pages got > less TLB pressure.
Hmm that's rather surprising to me. TLB caches the page table lookups and the PFN's of the physical pages it translates to shouldn't matter - the page tables will look the same. With 128 consecutive pages could manifest the reduced collision cache miss effect though. > -- > To unsubscribe, send a message with 'unsubscribe linux-mm' in > the body to majord...@kvack.org. For more info on Linux MM, > see: http://www.linux-mm.org/ . > Don't email: <a href=mailto:"d...@kvack.org";> em...@kvack.org </a> >
