| Message ID | 4BBB5543.40607@trash.net |
|---|---|
| State | Not Applicable, archived |
| Delegated to: | David Miller |
| Headers | show |
On Tuesday 06 April 2010 18:37:39 Patrick McHardy wrote: > Denys Fedorysychenko wrote: > > I notice on one of my QoS machines that HFSC start going out of bandwidth > > limits. The most terrible thing - it happens suddenly, and if i just > > relaunch QoS script - everything will work fine. > > That sounds like there's an overflow somewhere. > > > I'm not sure it is not my mistake, but most probably it is a bug. > > I can't tell for sure when it is happened, last kernel was on this > > machine 2.6.28 i guess, or maybe even older. > > Looking through the recent patches in this area, my prime suspect > is the attached patch. Does reverting it make any difference? > I will try to upgrade soon, it is critical router, so probably i will do this tonight. I guess with reverting this patch also it will hurt shaper resolution on high speeds... not a case for me, but for other people. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Tuesday 06 April 2010 18:37:39 Patrick McHardy wrote: > Denys Fedorysychenko wrote: > > I notice on one of my QoS machines that HFSC start going out of bandwidth > > limits. The most terrible thing - it happens suddenly, and if i just > > relaunch QoS script - everything will work fine. > > That sounds like there's an overflow somewhere. > > > I'm not sure it is not my mistake, but most probably it is a bug. > > I can't tell for sure when it is happened, last kernel was on this > > machine 2.6.28 i guess, or maybe even older. > > Looking through the recent patches in this area, my prime suspect > is the attached patch. Does reverting it make any difference? > Hi, i made sure - bug not related to this patch. I try to patch (also had to test latest stable release, to make sure it is appearing on it), and each test taking 1 day. If i "restart" script to resetup HFSC - it works for a while fine. At next day, peak time period - it goes wild. There is another thing also, i am going to try now, old kernel was 64-bit, but now 32bit, so i will try to shift to 64bit again. It can be not regression, but a bug. I guess not many people use HFSC, even it is definitely better than HTB. Or i'm wrong? -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
I am trying to track down HFSC bug. It seems, most probably it is related to PSCHED_SHIFT at the end, i am doing testing again. I will try to do complete clean build, maybe last time some .o was left or i forgot to do make clean. SM_SHIFT in HFSC is calculated as 30 - PSCHED_SHIFT, and it is shifted too much (or not enough) with new changes (ISM_SHIFT seems wrong too). So it is most probably overflow or not enough resolution. I will try to change PSCHED_SHIFT back to confirm that, and at least i found way to reproduce bug. Additionally in sch_hfsc.c i notice mentioned that PSCHED_SHIFT 10 is tick per 1024us, but i try to calculate their table (in source comments), it doesn't fit with my calculations based on 1024us/tick, but fits well with 1024 nanosecond. Is it was 1024ns per tick and now 64ns per tick? Or it is microseconds(us) ? -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On 10-05-20 03:34, Denys Fedorysychenko wrote: > I am trying to track down HFSC bug. > It seems, most probably it is related to PSCHED_SHIFT at the end, i am doing > testing again. I will try to do complete clean build, maybe last time some .o > was left or i forgot to do make clean. > > SM_SHIFT in HFSC is calculated as 30 - PSCHED_SHIFT, and it is shifted too > much (or not enough) with new changes (ISM_SHIFT seems wrong too). So it is > most probably overflow or not enough resolution. > I will try to change PSCHED_SHIFT back to confirm that, and at least i found > way to reproduce bug. > > Additionally in sch_hfsc.c i notice mentioned that PSCHED_SHIFT 10 is tick per > 1024us, but i try to calculate their table (in source comments), it doesn't > fit with my calculations based on 1024us/tick, but fits well with 1024 > nanosecond. > > Is it was 1024ns per tick and now 64ns per tick? Or it is microseconds(us) ? > -- In the old table (when PSCHED_SHIFT was 10) in the hfsc file, the requirements to keep 4 decimal digits were 20 and 18 for SM_ and ISM_ respectively. For the reference: * bits/sec 100Kbps 1Mbps 10Mbps 100Mbps 1Gbps * ------------+------------------------------------------------------- * bytes/1.024us 12.8e-3 128e-3 1280e-3 12800e-3 128000e-3 * 1.024us/byte 78.125 7.8125 0.78125 0.078125 0.0078125 * * So, for PSCHED_SHIFT 10 we need: SM_SHIFT 20, ISM_SHIFT 18. Considering the table - and if I didn't miss anything - they were swapped. psticks/byte in its "corner" case (0.0078125) requires 1e6, which corrsponds to ISM_SHIFT == 20. Similary, corner case for bytes/pstick (0.0128) requires 1e5, where SM_SHIFT == 17 would be sufficient. The above assuming pstick is 1.024us Currently, with PSCHED_SHIFT == 6 (so pstick is 64ns), the define macros actually hit the spot, giving following values: bytes/pstick: SM_SHIFT 24 (0.0008 @ 100kbit) psticks/byte: ISM_SHIFT 14 (0.125 @ 1gbit) But in generic case - the macros will not yield appropriate results - e.g. for PSCHED_SHIFT == 10, SM_SHIFT would be 20 and ISM_SHIFT would be 18 (not enough for 4 decimal digits). On a related subject - it would probably be desirable to consider smaller speeds than 100kbit, as adsl links with mere 128kbit upstream total are nothing out of ordinary. If we considered 10kbit as the reference value, we would need SM_SHIFT 27 to cover 0.00008 @ 10kbit. Not sure if 10gbit is desirable too - ISM_SHIFT would need 17 then. All assuming that 4 decimal digits is what we really need. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/include/net/pkt_sched.h b/include/net/pkt_sched.h index cd0e026..120935b 100644 --- a/include/net/pkt_sched.h +++ b/include/net/pkt_sched.h @@ -41,8 +41,8 @@ static inline void *qdisc_priv(struct Qdisc *q) typedef u64 psched_time_t; typedef long psched_tdiff_t; -/* Avoid doing 64 bit divide by 1000 */ -#define PSCHED_SHIFT 10 +/* Avoid doing 64 bit divide */ +#define PSCHED_SHIFT 6 #define PSCHED_US2NS(x) ((s64)(x) << PSCHED_SHIFT) #define PSCHED_NS2US(x) ((x) >> PSCHED_SHIFT)