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Re: 5.x filesystem performance regression
> [First figure missing is] a problem because that is what is required to show
> the effect of the buffer cache.
You mean, in order to compare it to the second figure?
I do remember it all took ages with 5.1. I'll go ahead and collect the missing
To speed things up, I won't test the influence of parity maps and don't do the
16k RAID 5 case.
> I always reboot between such tests to ensure that the buffer cache has been
> cleared out.
Doesn't re-mount-ing do the same thing?
> For some reason, RAID 5 appears to be very slow and it needs looking at.
Yes, that's where I originally started off. It didn't begin with fs-on-RAID-5
performance measurements but with why-is-my-machine-so-slow.
> If we want to look at the second runs in order to work out why 5.1 looks so
> much worse in the second runs, we still only have enough data in the
> plain disk and RAID 5 32k columns.
I'll collect some of the data. Oh, I already have 4.0.1 RAID 1 because of the
time -c measurements: 19s/12s. The 4.0.1 16k RAID 5 is missing, I won't
> Try comparing the output of "sysctl vm" on the two versions of NetBSD.
-vm.uspace = 20480
-vm.idlezero = 0
+vm.uspace = 12288
+vm.idlezero = 1
-vm.bufmem = 1117184
-vm.bufmem_lowater = 75479040
-vm.bufmem_hiwater = 603832320
+vm.bufmem = 1778688
+vm.bufmem_lowater = 75483648
+vm.bufmem_hiwater = 603869184
+vm.swapout = 1
> Once again RAID 5 appears to be very slow and it needs looking at.
Updated table, with only 32k bsize on RAID 5
The ``r'' rows have been measured with setcache r, i.e. write cache disabled.
plain disc RAID 1 RAID 5
4.0.1 softdep 64s 12s 19s 12s 54s 12s
4.0.1 softdep r 24s 18s 31s 10s 73s 14s
5.1 softdep 51s 42s 65s 60s 218s 250s
5.1 log 66s 30s 84s 25s 194s 190s
5.1 log r 201s 206s 249s 214s 201s 189s
5.99.52 log 26s 25s 90s 27s 368s 186s
Throuhput on the raw/block devices (dd if=/dev/zero bs=64k count=10000)
plain disc RAID 5
4.0.1 14M/s 6M/s 10M/s 33M/s
5.1 11M/s 6M/s 9M/s 32M/s
No, I did not mess up block/raw on the RAID 5. On the bare disc, the raw device
is faster (as expected), on the RAID, the block device is faster. Why?
Could anyone else please mesure on a RAID 5?
I sincerly hope someone can make sense out of these hours and hours of testing.
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