I'm seeing strange results on my device as well.

<6>[ 8070.839508] ramzswap: disk size not provided. You can use disksize_kb module
param to specify size.
<6>[ 8070.839569] Using default: (25% of RAM).
<6>[ 8070.855102] ramzswap: disk size set to 24468 kB
<6>[ 8085.402343] Adding 24464k swap on /dev/ramzswap0.  Priority:-1 extents:1
across:24464k SSD

# rzscontrol /dev/ramzswap0 -s
DiskSize:	25055232 kB
NumReads:	    2204
NumWrites:	     192
FailedReads:	       0
FailedWrites:	    2321
InvalidIO:	       0
PagesDiscard:	       0
ZeroPages:	       0
GoodCompress:	       0 %
NoCompress:	       0 %
PagesStored:	       0
PagesUsed:	       0
OrigDataSize:	       0 kB
ComprDataSize:	       0 kB
MemUsedTotal:	     117 kB

# free
              total         used         free       shared      buffers
  Mem:        97876        96280         1596            0          164
 Swap:        24464         2972        21492
Total:       122340        99252        23088
# cat /proc/swaps
Filename				Type		Size	Used	Priority
/dev/ramzswap0                          partition	24464	3140	-1

Please provide following data:
 - kernel logs
 - kernel config
 - /proc/meminfo
 - /proc/cpuinfo

I'm puzzled. Can you try 0.6pre2 so I know what code I should be looking at? Maybe I
just committed some junk when you pulled it.

Here ya go.  This is with 0.6pre2.  Stats looks the same as what I had pasted earlier
running off the HG branch.  The DiskSize output seems a bit odd too.

config.gz 9.3 KB   Download

cpuinfo.out 274 bytes   Download

kmsg.out 2.1 KB   Download

meminfo.out 868 bytes   Download

Just now I pushed changes that *may* solve this issue. Can you try this?
During compilation, You should get this warning: "Compiling on ARM".

I'm still seeing the same behavior.  Here are the other warnings during compile, not
sure if they'd be relevant..

  CC [M]  /home/chris/android/src/compcache/ramzswap.o
/home/chris/android/src/compcache/ramzswap.c:35:2: warning: #warning "Compiling on ARM"
/home/chris/android/src/compcache/ramzswap.c: In function 'ramzswap_set_disksize':
/home/chris/android/src/compcache/ramzswap.c:1237: warning: format '%lu' expects type
'long unsigned int', but argument 3 has type 'size_t'
/home/chris/android/src/compcache/ramzswap.c: In function 'ramzswap_set_memlimit':
/home/chris/android/src/compcache/ramzswap.c:1284: warning: format '%lu' expects type
'long unsigned int', but argument 3 has type 'size_t'

Fresh pull from hg and I get the same behavior as well.

> Fresh pull from hg and I get the same behavior as well.

I had inserted warning/error messages for every case where write failure can happen.
So, you must now have one of these messages in you logs. Can you upload logs from
this latest test? And also the output of 'rzscontrol /dev/ramzswap0 --stats'.

If there are still no warn/error messages in logs then it might be possible that
somehow stats being reported are simply junk and compcache is actually working fine.
I have this suspicion since "DiskSize" stat is showing weired values too.

I found 1 issue with stats. The stats structure is 256 bytes which was being
allocated on kernel stack! This can cause stats corruption. Now it is dynamically
allocated. 

Can you please try test version attached. Fixes include:
 - Alloc ioctl stats dynamically.
 - Flush cache for all uncompressed and zero filled pages too.

compcache-0.6_arm_test1.tar.gz 32.1 KB   Download

Here's what I got with the 0.6_arm_test1.  Not seeing any of the warnings/errors in
the logs for write failures either.

# ./rzscontrol /dev/ramzswap0 --stats
DiskSize:	25055232 kB
NumReads:	     122
NumWrites:	       3
FailedReads:	       0
FailedWrites:	     132
InvalidIO:	       0
PagesDiscard:	       0
ZeroPages:	       0
GoodCompress:	       0 %
NoCompress:	       0 %
PagesStored:	       0
PagesUsed:	       0
OrigDataSize:	       0 kB
ComprDataSize:	       0 kB
MemUsedTotal:	       9 kB

kmsg.out 1.3 KB   Download

meminfo.out 868 bytes   Download

Extremely weird. If swap writes were actually failing then kernel will throw out tons
of err/warnings - but we are not getting any such messages.

Put some memory load so it starts swapping to ramzswap. See if things crash. Also
observer output of /proc/swaps - this would give some hint if rzs if actually working
or not.

But how can we get junk in stats? I don't know yet - it all works fine on x86/x64.
Your output shows DiskSize in bytes while we print it out in KB. This is just so
weird since its not some arbitrary junk either -- how can it suddenly "forget"
conversion to KB??

haha I agree.  It seems very odd and so far nothing is crashing.  Swap does seem to
fill up more quickly but that's just a guess.  It's not filling fast enough to say
for sure either way.  I'll keep an eye on it and run some performance tests.  

Steve's output showed the kilobytes instead of bytes, though.  What could I possibly
do differently that would cause that?

Alright... running from a fresh ramzswap each time, so 0 used.  Ran mmap001
(http://www.arm.linux.org.uk/developer/stresstests.php) until it finished its tests.
 Here's the output at the end:


With 0.6
Filename				Type		Size	Used	Priority
/dev/ramzswap0                          partition	24464	24392	-1

With 0.5.3:
Filename				Type		Size	Used	Priority
/dev/ramzswap0                          partition	24464	16984	-1

I don't know why more swap is used with 0.6 but at least its seems to be working
fine. This narrows down the issue to stats corruption.

I guess my only concern was that the app was consuming the same amount of memory both
times and that I was seeing compression with .5 and no compression with .6.  I'll
have to do a little more digging in what the app is doing with memory though.  I
don't even know if that's a possibility that ramz could be storing uncompressed pages.  

Can you please try test version attached? It makes stats structure packed and
aligned(4). It also prints out stats to kern log. If stats are correct in logs but
not in direct output then it must be copy_to_user() which corrupting stats structure.

Thanks,
Nitin

compcache-0.6_arm_test2_align_stats.tar.gz 32.7 KB   Download

Looks like you were right.  The --stats output is still bad but here's the output
from the kernel logs:

<6>[54161.862152] DiskSize:	   24468 kB
<6>[54161.865753] NumReads:	     157
<6>[54161.865783] NumWrites:	    1627
<6>[54161.865783] FailedReads:	       0
<6>[54161.865783] FailedWrites:	       0
<6>[54161.865783] InvalidIO:	       0
<6>[54161.865783] PagesDiscard:	       0
<6>[54161.865814] ZeroPages:	      68
<6>[54161.865814] GoodCompress:	      65 %
<6>[54161.865814] NoCompress:	       5 %
<6>[54161.865814] PagesStored:	    1559
<6>[54161.865844] PagesUsed:	     626
<6>[54161.865844] OrigDataSize:	    6236 kB
<6>[54161.865844] ComprDataSize:	    2404 kB
<6>[54161.865844] MemUsedTotal:	    2504 kB

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Another try:

I just submitted change to now allocate rzscontrol stats on heap. This *might*
resolve the issue if allocation on stack was giving us unaligned pointer.

Please try latest commit. It prints some debug messages on stdout - so, please post
output of rzscontrol and also the kernel log.

/system/lib/modules # rzscontrol /dev/block/ramzswap0 --stats
debug: ret=0, stats_addr=0xb008, stats_sz=252
debug: 38368, 0, 0, 25051136
DiskSize:	       0 kB
NumReads:	       0
NumWrites:	      52
FailedReads:	       0
FailedWrites:	     422
InvalidIO:	       0
PagesDiscard:	       0
ZeroPages:	       0
GoodCompress:	       0 %
NoCompress:	       0 %
PagesStored:	       0
PagesUsed:	       0
OrigDataSize:	       0 kB
ComprDataSize:	       0 kB
MemUsedTotal:	      50 kB

I can now reproduce this issue on qemu ARM emulator! Lets hope we'll find this fix soon.

Now it works correctly, at least on QEMU ARM emulator. Can you please confirm if it
works correctly on actual h/w too? Thanks!

Output from emulator:

DiskSize:          31608 kB
NumReads:         170544
NumWrites:        170956
FailedReads:           0
FailedWrites:          0
InvalidIO:             0
PagesDiscard:      64491
ZeroPages:           190
GoodCompress:         98 %
NoCompress:            0 %
PagesStored:        7711
PagesUsed:           255
OrigDataSize:      30844 kB
ComprDataSize:       947 kB
MemUsedTotal:       1020 kB

Working great on an actual G1:

/ # rzscontrol /dev/block/ramzswap0 -s
DiskSize:	   24464 kB
NumReads:	     102
NumWrites:	     557
FailedReads:	       0
FailedWrites:	       0
InvalidIO:	       0
PagesDiscard:	       0
ZeroPages:	      52
GoodCompress:	      87 %
NoCompress:	       1 %
PagesStored:	     505
PagesUsed:	     132
OrigDataSize:	    2020 kB
ComprDataSize:	     517 kB
MemUsedTotal:	     528 kB


Thanks!!!!

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