On Sat, Nov 09, 2002 at 01:00:19PM +1100, Con Kolivas wrote:
> xtar_load:
> Kernel [runs] Time CPU% Loads LCPU% Ratio
> 2.4.18 [3] 150.8 49 2 8 2.11
> 2.4.19 [1] 132.4 55 2 9 1.85
> 2.4.19-ck9 [2] 138.6 58 2 11 1.94
> 2.4.20-rc1 [3] 180.7 40 3 8 2.53
> 2.4.20-rc1aa1 [3] 166.6 44 2 7 2.33
these numbers doesn't make sense. Can you describe what xtar_load is
doing?
> First noticeable difference. With repeated extracting of tars while compiling
> kernels 2.4.20-rc1 seems to be slower and aa1 curbs it just a little.
>
> io_load:
> Kernel [runs] Time CPU% Loads LCPU% Ratio
> 2.4.18 [3] 474.1 15 36 10 6.64
> 2.4.19 [3] 492.6 14 38 10 6.90
> 2.4.19-ck9 [2] 140.6 49 5 5 1.97
> 2.4.20-rc1 [2] 1142.2 6 90 10 16.00
> 2.4.20-rc1aa1 [1] 1132.5 6 90 10 15.86
What are you benchmarking, tar or the kernel compile? I think the
latter. That's the elevator and the size of the I/O queue here. Nothing
else. hacks like read-latency aren't very nice in particular with
async-io aware apps. If this improvement in ck9 was achieved decreasing
the queue size it'll be interesting to see how much the sequential I/O
is slowed down, it's very possible we've too big queues for some device.
> Well this is interesting. 2.4.20-rc1 seems to have improved it's ability to do
> IO work. Unfortunately it is now busy starving the scheduler in the mean
> time, much like the 2.5 kernels did before the deadline scheduler was put in.
>
> read_load:
> Kernel [runs] Time CPU% Loads LCPU% Ratio
> 2.4.18 [3] 102.3 70 6 3 1.43
> 2.4.19 [2] 134.1 54 14 5 1.88
> 2.4.19-ck9 [2] 77.4 85 11 9 1.08
> 2.4.20-rc1 [3] 173.2 43 20 5 2.43
> 2.4.20-rc1aa1 [3] 150.6 51 16 5 2.11
What is busy starving the scheduler? This sounds like it's again just an
evelator benchmark. I don't buy your scheduler claims, give more
explanations or it'll take it as vapourware wording, I very much doubt
you can find any single problem in the scheduler rc1aa2 or that the
scheduler in rc1aa1 has a chance to run slower than the one of 2.4.19 in
a I/O benchmark, ok it still misses the numa algorithm, but that's not a
bug, just a missing feature and it'll soon be fixed too and it doesn't
matter for normal smp non-numa machines out there.
> Also a noticeable difference, repeatedly reading a large file while trying to
> compile a kernel has slowed down in 2.4.20-rc1 and aa1 blunts this effect
> somewhat.
>
> list_load:
> Kernel [runs] Time CPU% Loads LCPU% Ratio
> 2.4.18 [3] 90.2 76 1 17 1.26
> 2.4.19 [1] 89.8 77 1 20 1.26
> 2.4.19-ck9 [2] 85.2 79 1 22 1.19
> 2.4.20-rc1 [3] 88.8 77 0 12 1.24
> 2.4.20-rc1aa1 [1] 88.1 78 1 16 1.23
>
> mem_load:
> Kernel [runs] Time CPU% Loads LCPU% Ratio
> 2.4.18 [3] 103.3 70 32 3 1.45
> 2.4.19 [3] 100.0 72 33 3 1.40
> 2.4.19-ck9 [2] 78.3 88 31 8 1.10
> 2.4.20-rc1 [3] 105.9 69 32 2 1.48
> 2.4.20-rc1aa1 [1] 106.3 69 33 3 1.49
again ck9 is faster because of elevator hacks ala read-latency.
in short your whole benchmark seems all about interacitivy of reads
during write flood. That's the read-latency thing or whatever else you
could do to ll_rw_block.c.
In short if somebody runs fast in something like this:
cp /dev/zero . & time cp bigfile /dev/null
he will win your whole contest too.
please show the difff between
2.4.19-ck9/drivers/block/{ll_rw_blk,elevator}.c and
2.4.19/drivers/block/...
All the difference is there and it will hurt you badly if you do
async-io benchmarks, and possibly dbench too. So you should always
accompain your benchmark with async-io simultanous read/write bandwitdth
and dbench, or I could always win your contest by shipping a very bad
kernel. Either that or change the name of your project, if somebody wins
this context that's probably a bad I/O scheduler in many other aspects,
some of the reason I didn't merge read-latency from Andrew.
Andrea
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This archive was generated by hypermail 2b29 : Fri Nov 15 2002 - 22:00:19 EST