Messages in this thread | | | From | Mary Edie Meredith <> | Subject | Re: DBT3-pgsql large performance improvement 2.6.6-rc1 | Date | Thu, 29 Apr 2004 16:50:06 -0700 |
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Mary Edie Meredith wrote: .snip > >>Mary Edie Meredith <maryedie@osdl.org> wrote: >> >>>Performance in DBT-3 (using PostgreSQL) has vastly >>>improved for _both in the "power" portion (single >>>process/query) and in the "throughput" portion of >>>the test (when the test is running multiple processes) >>>on our 4-way(4GB) and 8-way(8GB) STP systems as >>>compared 2.6.5 kernel results. >>> >>>Using the default DBT-3 options (ie using LVM, ext2, >>>PostgreSQL version 7.4.1) >>> >>>Note: Bigger numbers are better. >>> >>>Kernel....Runid..CPUs.Power..%incP.Thruput %incT >>>2.6.5 291308 4 97.08 base 120.46 base >>>2.6.6-rc1 291876 4 146.11 50.5% 222.94 85.1% >>> >>>Kernel....Runid..CPUs.Power..%incP..Thruput %incT >>>2.6.5 291346 8 101.08 base 138.95 base >>>2.6.6-rc1 291915 8 151.69 50.1% 273.69 97.0% >>> >>>So the improvement is between 50% and 97%! >> >>How odd.
Your instincts were right (as usual).
We took another closer look at this. It appears that a change slipped into the kit around April 13, which probably made this stunning performance difference not the kernel.
Results of second run of the linux-2.6.5 kernel using the changed test kit showed that the numbers are comparable to the latest 2.6.6-rc3 release. Therefore, it looks like the initial improvements posted were most likely due to the change in datatypes making the database size smaller, among other things.
....................Composite....Power...Throughput
initial linux 2.6.5 108.14 97.08 120.46 second linux 2.6.5 180.62 146.53 222.63 linux 2.6.6-rc3 181.83 147.16 224.68
Tests were compared on 4-way systems. (Bigger is better).
We will run the 8-way numbers over night to see if there is any difference for those systems. We are also running some IA64 results over night as well.
>> >> >>>Profile 2.6.5 8way throughput phase: >>>http://khack.osdl.org/stp/291346/profile/after_throughput_test_1-tick.sort >>>Profile 2.6.6-r1 8way throughput phase: >>>http://khack.osdl.org/stp/291915/profile/after_throughput_test_1-tick.sort >> >>Odder. do_anonymous_page() is doing 10x more work in 2.6.6-rc1. And the >>CPU scheduler cost has fallen a lot. >> >>Frankly, I can't think of anything in 2.6.6-rc1 which would cause either of >>these things! >> >> >>>What I notice is that radix_tree_lookup is in >>>the top 20 in the 2.6.5 profile, but not in >>>2.6.6-rc1. Could theradix tree changes be >>>responsible for this? >> >>I would certainly expect 2x or even higher throughput increases from either >>the writeback changes or the ext2&ext3 fsync changes. >> >> >>>DBT-3 is a read mostly DSS workload and the throughput >>>phase is where we run multiple query streams (as >>>many as we have CPUs). In this workload, the database >>>is stored on a file system, but it is small relative >>>to the amount of memory (4GB and 8GB). It almost >>>completely caches in page cache early on. So there >>>is some physical IO in the first few minutes, but very >>>little to none in the remainder. >> >>But you're not doing a significant amount of writing during the test, so >>scrub that theory. >> >>Do you have full reports anywhere? I'd be interested in seeing a vmstat >>trace from the entire run, both 2.6.5 and 2.6.6-rc1. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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