Thanks for reply, Stephen.
I'm in x86-64, my cpu is `Intel(R) Xeon(R) CPU E5-2620 v3 @ 2.40GHz`. When allocation mbuf in program1, and transfer it to program2 for free via ring, the program1 might meet assert in allocate mbuf sometimes. (`RTE_ASSERT(rte_mbuf_refcnt_read(m) == 0);`) but when I using gdb to check it, the refcnt field of mbuf is already zero. so I believe the problem came from the cache line problem or incorrect optimization. When apply this patch, the problem seems solved. I'm submitting it for your comments. 2016-09-03 0:12 GMT+08:00 Stephen Hemminger <stephen at networkplumber.org>: > On Fri, 2 Sep 2016 13:25:06 +0800 > lilinzhe <slayercat.subscription at gmail.com> wrote: > >> From: ??? <lilinzhe at ijinshan.com> >> >> chagne atomic ref update to always call atomic_add >> >> when mbuf is allocated by cpu1 and freed by cpu2. cpu1 cache may not be >> updated by such a set operation. >> causes refcnt reads incorrect values. > > What architecture are you dealing with? On X86 memory is cache coherent. > > Doing atomic operation all the time on each mbuf free would significantly > slow down performance. >
