On 2020-03-09 08:17, Jerin Jacob Kollanukkaran wrote: >> -----Original Message----- >> From: Mattias Rönnblom <mattias.ronnb...@ericsson.com> >> Sent: Monday, March 9, 2020 12:21 PM >> To: Jerin Jacob Kollanukkaran <jer...@marvell.com> >> Cc: dev@dpdk.org; stefan.sundkv...@ericsson.com; ola.liljed...@arm.com; >> Mattias Rönnblom <mattias.ronnb...@ericsson.com> >> Subject: [PATCH 5/8] event/dsw: avoid migration waves in large systems >> >> ---------------------------------------------------------------------- >> DSW limits the rate of migrations on a per-port basis. Hence, as the number >> of >> cores grows, so does the total migration capacity. >> >> In high core-count systems, this allows for a situation where flows are >> migrated >> to a lightly loaded port which recently already received a number of new >> flows >> (from other ports). The processing load generated by these new flows may not >> yet be reflected in the lightly loaded port's load estimate. The result is >> that the >> previously lightly loaded port is now overloaded. >> >> This patch adds a rough estimate of the size of the inbound migrations to a >> particular port, which can be factored into the migration logic, avoiding the >> above problem. >> >> Signed-off-by: Mattias Rönnblom <mattias.ronnb...@ericsson.com> >> --- >> @@ -491,6 +502,9 @@ dsw_select_emigration_target(struct dsw_evdev *dsw, >> target_qfs[*targets_len] = *candidate_qf; >> (*targets_len)++; >> >> + rte_atomic32_add(&dsw->ports[candidate_port_id].immigration_load, >> + candidate_flow_load); > These are the full barriers in arm64 and PowerPC. > Request to change the C11 mem model[1] with Load and acquire semantics > For better performance enhancement on non x86 machines. > > drivers/event/opdl is already moved to C11 mem model. > > [1] > https://gcc.gnu.org/onlinedocs/gcc/_005f_005fatomic-Builtins.html > The performance impacts would be small, since this is in the slow path, with something like a handful of memory barrier per core per ms.
Arguably, it could be done for consistency reasons, but then you should change all DSW atomics. >> + >> return true;
