[Galaxy Tab  Android Development] daniel.weck:
I've adapted the original performance tweaks by 'hardcore' @ XDA for my overclocked/undervolted Galaxy Tab. The tweaked values are pretty much the same as the ones recommended by the original poster, but my simple init.d/ script allows me to log default system values when pushing new values, which is useful for debugging. The script also contains comments to describe the role of each setting. Note that if you don't have init.d/ support in your kernel / initramfs, you can still run the script manually at each system start (use an app like GScript).

#!/system/bin/sh
#
# Original tweaks by 'hardcore' @ XDA
# http://xdaforums.com/showthread.php?t=813309

# This is a startup script designed for /system/etc/init.d/.
# Note that "run-parts" support (for init.d/ scripts) is normally provided by custom a initramfs,
# which should bundle busybox in /sbin/. The /sbin/run-parts.sh script should take care of
# running init scripts (by calling /sbin/runparts), and it should subsequently trigger
# the device startup (using "setprop filesystem.ready 1", or similar).
# Note that the recovery mode typically doesn't run /system/etc/init.d/ startup scripts.

# Ensure /sbin/busybox takes precedence.
# Normally this is redundant, because the /init.rc startup script already sets the correct path.
export PATH=/sbin:$PATH

# Logging of old/new sysfs values, useful for double-checking.
logFile=/data/local/tmp/S_perf_tweaks.log

if [ -f $logFile ]
then
rm $logFile
fi

touch $logFile

# This function logs the old value and writes the new value.
echo_()
{
echo '' >> $logFile
echo -n "${2}${3} (${1}): " >> $logFile
#head -1 ${2}${3} >> $logFile
#read $firstLine < ${2}${3}
#echo -n $firstLine >> $logFile
contents=`echo -n $(cat ${2}${3})`
echo -n $contents >> $logFile
echo -n " ---> " >> $logFile
echo $1 > ${2}${3}
contents=`echo -n $(cat ${2}${3})`
echo -n $contents >> $logFile
}

# Note that the settings pushed by VoltageControl.apk
# could also be managed here (this only applies to kernels with clock/frequency tables and undervolt sysfs support):
#echo_ "50 50 50 25 25 25 25 " "/sys/devices/system/cpu/cpu0/cpufreq" "/UV_mV_table"
#echo_ 1400000 "/sys/devices/system/cpu/cpu0/cpufreq" "/scaling_max_freq"

echo "---------" >> $logFile

# Remount all partitions that use relatime with noatime and nodiratime instead.
# Note: atime generates a write-after-every-read, relatime is an optimized version of atime.
for k in $(mount | grep relatime | cut -d " " -f3)
do
echo "mount -o remount,noatime,nodiratime $k" >> $logFile
sync
mount -o remount,noatime $k
done

# Here is a sample test to measure read/write performance on rfs partitions:
### test for write: dd if=/dev/zero of=/data/test count=30000
### test for read: dd if=/data/test of=/dev/zero

echo "---------" >> $logFile

# Log the mount table
mount >> $logFile

echo "---------" >> $logFile

# Optimize the cfq/bfq I/O scheduler for flash memory (defaults are designed for spinning harddisks).
# Lower the idle wait, re-enable the low latency mode, remove the penalty for back-seeks,
# and explicitly tell the kernel that the storage is not a spinning disk.

for i in $(ls -1 /sys/block/stl*) $(ls -1 /sys/block/mmc*) $(ls -1 /sys/block/bml*) $(ls -1 -d /sys/block/tfsr*)
#for i in `ls /sys/block/stl* /sys/block/mmc* /sys/block/bml* /sys/block/tfsr*`;
do
# DEF noop anticipatory deadline cfq [bfq]
echo_ "bfq" $i "/queue/scheduler"

# DEF 1 ?
echo_ "0" $i "/queue/rotational"

# DEF 1 ?
echo_ "1" $i "/queue/iosched/low_latency"

# DEF 2 ?
echo_ "1" $i "/queue/iosched/back_seek_penalty"

# DEF 16384 ?
echo_ "1000000000" $i "/queue/iosched/back_seek_max"

# DEF 6 ?
echo_ "3" $i "/queue/iosched/slice_idle"

sync
done

# Set tendency of kernel to swap to minimum, since swap isn't used anyway.
# (swap = move portions of RAM data to disk partition or file, to free-up RAM)
# (a value of 0 means "do not swap unless out of free RAM", a value of 100 means "swap whenever possible")
# (the default is 60 which is okay for normal Linux installations)

# DEF 60
echo_ "0" "/proc/sys/vm" "/swappiness"

# Lower the amount of unwritten write cache to reduce lags when a huge write is required.

# DEF 20
echo_ "10" "/proc/sys/vm" "/dirty_ratio"

# Increase minimum free memory, in theory this should make the kernel less likely to suddenly run out of memory.

# DEF 3102
echo_ "4096" "/proc/sys/vm" "/min_free_kbytes"

# Increase tendency of kernel to keep block-cache to help with slower RFS filesystem.

# DEF 100
echo_ "1000" "/proc/sys/vm" "/vfs_cache_pressure"

# Increase the write flush timeouts to save some battery life.

# DEF 250
echo_ "2000" "/proc/sys/vm" "/dirty_writeback_centisecs"

# DEF 200
echo_ "1000" "/proc/sys/vm" "/dirty_expire_centisecs"

# Make the task scheduler more 'fair' when multiple tasks are running,
# which improves user-interface and application responsiveness.

# DEF 10000000
echo_ "20000000" "/proc/sys/kernel" "/sched_latency_ns"

# DEF 2000000
echo_ "2000000" "/proc/sys/kernel" "/sched_wakeup_granularity_ns"

# DEF 1000000
echo_ "1000000" "/proc/sys/kernel" "/sched_min_granularity_ns"

sync

# Miscellaneous tweaks
setprop dalvik.vm.startheapsize 8m
#setprop wifi.supplicant_scan_interval 90

echo '' >> $logFile
echo "---------" >> $logFile

#This apply a tweaked deadline scheduler to all RFS (and ext2/3/4, if existent) partitions.
#for i in /sys/block/*
#do
# DEF noop anticipatory deadline cfq [bfq]
#echo deadline > $i/queue/scheduler

#echo 4 > $i/queue/iosched/writes_starved
#echo 1 > $i/queue/iosched/fifo_batch
#echo 256 > $i/queue/nr_requests
#done