Messages in this thread |  | | | Date | Tue, 30 Dec 2003 14:16:55 -0600 | | From | Andy Isaacson <> | | Subject | Re: [PATCH] 2.6.0 - Watchdog patches (BK consistency checks) |
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On Tue, Dec 30, 2003 at 12:56:32PM -0700, Eric D. Mudama wrote: > On Tue, Dec 30 at 13:13, Andy Isaacson wrote: > >On Tue, Dec 30, 2003 at 08:36:15AM -0500, Ed Tomlinson wrote: > >The consistency check definitely should not take 15 minutes. It should > >be (much) less than 30 seconds. What is the hardware you're running on? > > > >I'm running on an Athlon 2 GHz (XP 2400+) with 512MB and a 7200RPM IDE > >disk, and I can do a complete clone (with full data copy and consistency > >check) of the 2.4 tree in 1:40. That was with cold caches; with the > >sfile copies and "checkout:get", a half-gig isn't enough to cache > >everything. The consistency check is about 19 seconds (bk -r check -acv). > > For what it is worth: > > AMD Duron 950MHz, 768MB RAM > 7200RPM 80GB Quantum Viper IDE drive, 26% full > > phat-penguin:~/src/linux-2.5> time bk -r check -acv > 100% |=================================================================| OK > 42.710u 5.770s 2:04.63 38.8% 0+0k 0+0io 74078pf+0w > > over 2 minutes of wall time, 42 seconds of "user" time... (if I'm reading it right), without primed disk caches. > > The 2nd run, half a minute later: > > phat-penguin:~/src/linux-2.5> time bk -r check -acv > 100% |=================================================================| OK > 41.900u 3.080s 0:45.53 98.7% 0+0k 0+0io 74078pf+0w > > > ...would appear to show that BK's checksumming, on my system, is > constrained near 41 seconds of calculation time, and the difference > between the user and the wall-clock time is basically time spent > waiting for the disk to do all its reads. > > > I guess in that case, it'd be interesting to see what the user and > wall times were for the original poster who reported a 15+ minute > integrity check.
That's basically right, except that if you don't have enough memory to keep bk's working set in memory, then you're paging and performance starts to suck.
I didn't realize that the cpu-bound portion of the check would scale so closely with CPU speed, but it looks like the scaling is almost dead-on; 18.4/41.9 = .439 950/2000 = .475
So I was wrong to say "less than 30 seconds". "If you have a fast CPU and enough memory", I guess. But the memory matters a lot more than the CPU.
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