Re: Hyperthreading (was: Two identical systems, radically different performance)

For your amusement ... I upgraded from 8.4.4 to 9.2.1 results. Threw away
the DB completely and did a new init. Same hardware, postgres.conf and
Linux as before.

ra is "blockdev --getra" (both PGDATA and XLOG disks)
walb is postgres.conf "wal_buffers"

ra:8192 walb:1M ra:256 walb:1M ra:256 walb:256kB
---------------- ---------------- -----------------
-c -t Run1 Run2 Run3 Run4 Run5 Run6 Run7 Run8 Run9
5 20000 1963 2103 2145 2292 2312 2353 2296 2175 2294
10 10000 2587 2749 2762 3252 3265 3276 3267 3228 3263
20 5000 3449 3578 3438 4910 4958 4949 4949 4927 4943
30 3333 4222 3731 3992 6929 6924 6562 6754 6995 6869
40 2500 4261 3722 4243 9286 9240 5712 9310 8530 8872
50 2000 4138 4399 3865 9213 9351 9578 8011 7651 8362

Unfortunately, distance prevents me from going to the co-location facility
and trying this with hyperthreading turned back on.

Craig

On Tue, Oct 9, 2012 at 1:12 PM, Craig James <cjames(at)emolecules(dot)com> wrote:

> I've confirmed that hyperthreading causes a huge drop in performance on a
> 2x4-core Intel Xeon E5620 2.40GHz system. The bottom line is:
>
> ~3200 TPS max with hyperthreading
> ~9000 TPS max without hyprethreading
>
> Here are my results.
>
> "Hyprethreads" (Run1) is "out of the box" with hyperthreads enabled. Only
> one column of hyperthread results are shown, but prior to today's work I
> ran this a dozen or so times, and "Run1" is very representative of all
> those runs. I also rebooted and confirmed that rebooting had no effect.
>
> "+NoHyperthreads" (Run2-5) involved rebooting into the BIOS and disabling
> hyperthreads.
>
> "+NoAutoVacuum" (Run6-8) means I turned off autovacuum in the
> postgresql.conf file and restarted Postgres (with hyperthreads still
> disabled).
>
> Hyperthreads +NoHyperthreads +NoAutoVacuum
> ------------ ---------------------- ----------------
> -c -t Run1 Run2 Run3 Run4 Run5 Run6 Run7 Run8
> 5 20000 2733 2152 2352 2398 2769 2767 2777 4463
> 10 10000 2783 2404 3529 3365 4397 4457 4217 4172
> 20 5000 3241 3128 3728 5170 5253 5252 4832 8123
> 30 3333 2987 5699 6180 8173 8259 6435 8225 8123
> 40 2500 2739 7133 6507 9298 7845 9133 9298 9230
> 50 2000 2119 5420 5020 8411 5670 9344 7624 8304
>
> I'll be upgrading to 8.4.14 and making more changes to postgres.conf based
> on feedback. The server is available for a day or so for more tests if
> anyone has suggestions.
>
> Here's how I got these results:
>
> su postgres
> unset LANG
> export LD_LIBRARY_PATH=/usr/local/pgsql/lib
> /usr/local/pgsql/bin/initdb --pgdata=/data/postgres/main \
> --xlogdir=/postgres_xlog/xlog --username=postgres
>
> Edit config file:
>
> max_connections = 500
> shared_buffers = 1000MB
> work_mem = 128MB
> synchronous_commit = off
> full_page_writes = off
> wal_buffers = 256kB
> checkpoint_segments = 30
> effective_cache_size = 4GB
> track_activities = on
> track_counts = on
> track_functions = none
> autovacuum = on
> autovacuum_naptime = 5min
> escape_string_warning = off
>
> createuser -U postgres test
> createdb -U postgres -O test test
>
> pgbench -i -s 100 -U test
> for p in "5 20000" "10 10000" "20 5000" "30 3333" "40 2500" "50 2000" ; do
> echo
> c=`echo $p | cut -d' ' -f1`
> t=`echo $p | cut -d' ' -f2`
> cmd="pgbench -U test -c $c -t $t"
> echo "--------- $cmd ---------"
> $cmd
> done
>
> The hardware:
>
> CPU: 2x4-core Intex Xeon E5620 2.40 GHz
>
> Memory: 12 GB DDR EC
>
> Disks: 12x500GB disks (Western Digital 7200RPM SATA)
> XLOG: 2 disks, RAID1 ext2
> PGDATA: 8 disks, RAID10
>
> 3WARE 9650SE-12ML with battery-backed cache. The admin tool (tw_cli)
> indicates that the battery is charged and the cache is working on both
> units.
>
> Linux: 2.6.32-41-server #94-Ubuntu SMP (new server's disk was
> actually cloned from old server).
>
> Postgres: 8.4.4
>
> Craig
>