On Tue, Sep 20, 2022 at 02:23:09PM +0800, Wen Gu wrote: > > >On 2022/9/20 12:55, dust.li wrote: > >> On Tue, Sep 20, 2022 at 10:53:54AM +0800, Wen Gu wrote: >> > SMC-R tests the viability of link by sending out TEST_LINK LLC >> > messages over RoCE fabric when connections on link have been >> > idle for a time longer than keepalive interval (testlink time). >> > >> > But using tcp_keepalive_time as testlink time maybe not quite >> > suitable because it is default no less than two hours[1], which >> > is too long for single link to find peer dead. The active host >> > will still use peer-dead link (QP) sending messages, and can't >> > find out until get IB_WC_RETRY_EXC_ERR error CQEs, which takes >> > more time than TEST_LINK timeout (SMC_LLC_WAIT_TIME) normally. >> > >> > So this patch introduces a independent sysctl for SMC-R to set >> > link keepalive time, in order to detect link down in time. The >> > default value is 30 seconds. >> > >> > [1] https://www.rfc-editor.org/rfc/rfc1122#page-101 >> > >> > Signed-off-by: Wen Gu <guwen@xxxxxxxxxxxxxxxxx> >> > --- > >> > /* called after lgr was removed from lgr_list */ >> > diff --git a/net/smc/smc_llc.h b/net/smc/smc_llc.h >> > index 4404e52..1de9a29 100644 >> > --- a/net/smc/smc_llc.h >> > +++ b/net/smc/smc_llc.h >> > @@ -19,6 +19,7 @@ >> > >> > #define SMC_LLC_WAIT_FIRST_TIME (5 * HZ) >> > #define SMC_LLC_WAIT_TIME (2 * HZ) >> > +#define SMC_LLC_TESTLINK_DEFAULT_TIME 30 >> >> I'm wondering why we don't follow the upper to macros using (30 * HZ) ? >> >Thanks for the reivew. > >Because the value of sysctl_smcr_testlink_time is in seconds, and the value >of llc_testlink_time is jiffies. > >I have thought about >1) using proc_dointvec_jiffies as sysctl's proc_handler just like TCP does. > But proc_dointvec_jiffies has no minimum limit, value 0 makes no sense for SMC testlink. Maybe 0 means disable the LLC TEST LINK ? >2) using proc_dointvec_ms_jiffies_minmax as proc_handler. But millisecond interval > seems expensive for SMC test link. > >So, I choose to use proc_dointvec_minmax, make sysctl_smcr_testlink_time in >seconds, and convert to jiffies when assigning to llc_testlink_time. If proc_dointvec_jiffies_minmax is really the problem, maybe you can write your own proc handler. Thanks
