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Ip=[63.35.35.123]; Helo=[64aa7808-outbound-1.mta.getcheckrecipient.com] X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: HE1PR0801MB1850 Subject: Re: [dpdk-dev] [RFC PATCH 3/3] lib/lpm: integrate RCU QSBR X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org Sender: "dev" > -----Original Message----- > From: Stephen Hemminger > Sent: Friday, August 23, 2019 09:23 > To: Ruifeng Wang (Arm Technology China) > Cc: bruce.richardson@intel.com; vladimir.medvedkin@intel.com; > olivier.matz@6wind.com; dev@dpdk.org; Honnappa Nagarahalli > ; Dharmik Thakkar > ; nd > Subject: Re: [dpdk-dev] [RFC PATCH 3/3] lib/lpm: integrate RCU QSBR >=20 > On Thu, 22 Aug 2019 14:34:57 +0800 > Ruifeng Wang wrote: >=20 > > Currently, the tbl8 group is freed even though the readers might be > > using the tbl8 group entries. The freed tbl8 group can be reallocated > > quickly. This results in incorrect lookup results. > > > > RCU QSBR process is integrated for safe tbl8 group reclaim. > > Refer to RCU documentation to understand various aspects of > > integrating RCU library into other libraries. > > > > Signed-off-by: Ruifeng Wang > > Reviewed-by: Honnappa Nagarahalli > > Reviewed-by: Gavin Hu >=20 > Having RCU in LPM is a good idea but difficult to find out how to do it i= n DPDK. > Not everyone wants to use RCU, so making a required part of how LPM is > used will impact users. LPM users will not be imposed to use RCU. New API is provided to enable the= RCU functionality in LPM library. For users not using RCU, code path is intact,= and there will be no performance drop. >=20 > Also, it looks like DPDK RCU lacks a good generic way to handle deferred = free. > Having to introduce a ring to handle is adding more complexity when a > generic solution would be better (see userspace RCU library for example). > Other parts of DPDK would benefit if deferred free was done better. This requires support from RCU library.=20 Needs Honnappa's comment.