Announce: ccache release 0.1

Announce: ccache release 0.1

[Nitin Gupta]

Hi All,

I am excited to announce first release of ccache - Compressed RAM
based swap device for Linux (2.6.x kernel).
  - Project home: http://code.google.com/p/ccache/
  - ccache-0.1: http://ccache.googlecode.com/files/ccache-0.1.tar.bz2

This is RAM based block device which acts as swap disk. Pages swapped
to this device are compressed and stored in memory itself. This is
especially useful for swapless embedded devices. Also, flash storage
typically used in embedded devices suffer from wear-leveling issues -
so, its very useful if we can avoid using them as swap device.
And yes, its useful for desktops too :)

It does not require any kernel patching. All components are separate
kernel modules:
- Memory allocator (tlsf.ko)
- Compressor (lzo1x_compress.ko)
- Decompressor (lzo1x_decompress.ko)
- Main ccache module (ccache.ko)
(LZO de/compressor is already in mainline but I have included it here
since distros don't ship it by default).
README (or project home) explains compilation and usage in detail.

Some performance numbers for allocator and de/compressor can be found
on project home. Currently it is tested on Linux kernel 2.6.23.x and
2.6.25-rc2 (x86 only). Please mail me/mailing-list any
issues/suggestions you have.

Code reviews will be really helpful! :)

Thanks,
- Nitin

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Re: [linux-mm-cc] Announce: ccache release 0.1

[John McCabe-Dansted]

On Feb 19, 2008 6:39 AM, Nitin Gupta <nitingupta910@gmail.com> wrote:
> Some performance numbers for allocator and de/compressor can be found
> on project home. Currently it is tested on Linux kernel 2.6.23.x and
> 2.6.25-rc2 (x86 only). Please mail me/mailing-list any
> issues/suggestions you have.

It caused Gutsy (2.6.22-14-generic) to crash when I did a swap off of
my hdd swap. I have a GB of ram, so I would have been fine without
ccache.

I had swapped on a 400MB ccache swap.

BTW, why is the default 10% of mem? This refers to the size of the
block device right? So even 100% would probably only use 50% of
physical memory for swap, assuming a 2:1 compression ratio.

-- 
John C. McCabe-Dansted
PhD Student
University of Western Australia

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Re: [linux-mm-cc] Announce: ccache release 0.1

[Nitin Gupta]

On Feb 19, 2008 4:03 PM, John McCabe-Dansted <gmatht@gmail.com> wrote:
> On Feb 19, 2008 6:39 AM, Nitin Gupta <nitingupta910@gmail.com> wrote:
> > Some performance numbers for allocator and de/compressor can be found
> > on project home. Currently it is tested on Linux kernel 2.6.23.x and
> > 2.6.25-rc2 (x86 only). Please mail me/mailing-list any
> > issues/suggestions you have.
>
> It caused Gutsy (2.6.22-14-generic) to crash when I did a swap off of
> my hdd swap. I have a GB of ram, so I would have been fine without
> ccache.

These days "desktops with small memory" probably means virtual
machines with, say, <512M RAM :-)

>
> I had swapped on a 400MB ccache swap.
>

I need /var/log/messages (or whatever file kernel logs to in Gutsy) to
debug this.
Please send it to me offline if its too big.

> BTW, why is the default 10% of mem?

I have no great justification for "10%".

> This refers to the size of the
> block device right? So even 100% would probably only use 50% of
> physical memory for swap, assuming a 2:1 compression ratio.
>

Yes, this is correct.

Thanks,
- Nitin

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Re: [linux-mm-cc] Announce: ccache release 0.1

[John McCabe-Dansted]

On Feb 19, 2008 9:06 PM, Nitin Gupta <nitingupta910@gmail.com> wrote:
> On Feb 19, 2008 4:03 PM, John McCabe-Dansted <gmatht@gmail.com> wrote:
> > On Feb 19, 2008 6:39 AM, Nitin Gupta <nitingupta910@gmail.com> wrote:
> > > Some performance numbers for allocator and de/compressor can be found
> > > on project home. Currently it is tested on Linux kernel 2.6.23.x and
> > > 2.6.25-rc2 (x86 only). Please mail me/mailing-list any
> > > issues/suggestions you have.
> >
> > It caused Gutsy (2.6.22-14-generic) to crash when I did a swap off of
> > my hdd swap. I have a GB of ram, so I would have been fine without
> > ccache.
>
> These days "desktops with small memory" probably means virtual
> machines with, say, <512M RAM :-)

The Hardy liveCD is really snappy with a 192MB VM and and a 128MB
ccache swap. :)

> > I had swapped on a 400MB ccache swap.
> >
>
> I need /var/log/messages (or whatever file kernel logs to in Gutsy) to
> debug this.
> Please send it to me offline if its too big.

This seems to be the bit you want:

ubuntu-xp syslogd 1.4.1#21ubuntu3: restart.
Feb 19 08:07:31 ubuntu-xp -- MARK --
...
Feb 19 18:47:31 ubuntu-xp -- MARK --
Feb 19 18:59:51 ubuntu-xp kernel: [377208.185464] ccache: Unknown
symbol lzo1x_decompress_safe
Feb 19 18:59:51 ubuntu-xp kernel: [377208.185518] ccache: Unknown
symbol lzo1x_1_compress
Feb 19 18:59:51 ubuntu-xp kernel: [377208.185660] ccache: Unknown
symbol tlsf_free
Feb 19 18:59:51 ubuntu-xp kernel: [377208.185759] ccache: Unknown
symbol tlsf_malloc
Feb 19 18:59:51 ubuntu-xp kernel: [377208.185836] ccache: Unknown
symbol tlsf_destroy_memory_pool
Feb 19 18:59:51 ubuntu-xp kernel: [377208.185903] ccache: Unknown
symbol tlsf_create_memory_pool
Feb 19 19:00:10 ubuntu-xp kernel: [377227.049613] ccache: Unknown
symbol lzo1x_decompress_safe
Feb 19 19:00:10 ubuntu-xp kernel: [377227.049667] ccache: Unknown
symbol lzo1x_1_compress
Feb 19 19:00:10 ubuntu-xp kernel: [377227.049815] ccache: Unknown
symbol tlsf_free
Feb 19 19:00:10 ubuntu-xp kernel: [377227.049913] ccache: Unknown
symbol tlsf_malloc
Feb 19 19:00:10 ubuntu-xp kernel: [377227.049989] ccache: Unknown
symbol tlsf_destroy_memory_pool
Feb 19 19:00:10 ubuntu-xp kernel: [377227.050055] ccache: Unknown
symbol tlsf_create_memory_pool
Feb 19 19:01:07 ubuntu-xp kernel: [377283.369080] ccache: Compressed
swap size set to: 409600 KB
Feb 19 19:01:07 ubuntu-xp kernel: [377283.370015] TLSF: pool:
f8c11000, init_size=16384, max_size=0, grow_size=16384
Feb 19 19:02:21 ubuntu-xp kernel: [377358.145969] Adding 409596k swap
on /dev/ccache.  Priority:1 extents:1 across:409596k
Feb 19 19:02:57 ubuntu-xp kernel: [377393.198473] f8c0003c
Feb 19 19:02:57 ubuntu-xp kernel: [377393.198486] Modules linked in: ccache tlsf
 lzo1x_decompress lzo1x_compress atl2 af_packet binfmt_misc rfcomm l2cap bluetoo
th vboxdrv ppdev ipv6 i915 drm acpi_cpufreq cpufreq_conservative cpufreq_userspa
ce cpufreq_powersave cpufreq_ondemand cpufreq_stats freq_table video container s
bs button dock ac battery reiserfs nls_iso8859_1 nls_cp437 vfat fat w83627ehf i2
c_isa i2c_core lp snd_hda_intel snd_pcm_oss snd_mixer_oss snd_pcm snd_seq_dummy
snd_seq_oss snd_seq_midi snd_rawmidi snd_seq_midi_event snd_seq pcspkr serio_raw
 snd_timer snd_seq_device parport_pc parport psmouse xpad intel_agp usblp iTCO_w
dt iTCO_vendor_support agpgart snd soundcore snd_page_alloc shpchp pci_hotplug e
vdev usb_storage ide_core ext3 jbd mbcache usbhid hid sg sr_mod cdrom sd_mod ata
_generic libusual ata_piix floppy ohci1394 ieee1394 ehci_hcd libata scsi_mod uhc
i_hcd usbcore thermal processor fan fuse apparmor commoncap fbcon tileblit font
bitblit softcursor
Feb 19 19:05:25 ubuntu-xp syslogd 1.4.1#21ubuntu3: restart.
...

> > BTW, why is the default 10% of mem?
>
> I have no great justification for "10%".

Perhaps 100% (or maybe 50%) would be a more sensible default? For me
66% makes a huge difference to the Hardy liveCD performance. 10% makes
a difference but 50%+ goes from "ls /" taking 10s to snappy
performance even on large applications like Firefox.

> > This refers to the size of the
> > block device right? So even 100% would probably only use 50% of
> > physical memory for swap, assuming a 2:1 compression ratio.
>
> Yes, this is correct.
>
> Thanks,
> - Nitin

-- 
John C. McCabe-Dansted
PhD Student
University of Western Australia

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Re: [linux-mm-cc] Announce: ccache release 0.1

[Nitin Gupta]

On Feb 19, 2008 6:37 PM, John McCabe-Dansted <gmatht@gmail.com> wrote:
> On Feb 19, 2008 9:06 PM, Nitin Gupta <nitingupta910@gmail.com> wrote:
> > On Feb 19, 2008 4:03 PM, John McCabe-Dansted <gmatht@gmail.com> wrote:
> > > On Feb 19, 2008 6:39 AM, Nitin Gupta <nitingupta910@gmail.com> wrote:
> > > > Some performance numbers for allocator and de/compressor can be found
> > > > on project home. Currently it is tested on Linux kernel 2.6.23.x and
> > > > 2.6.25-rc2 (x86 only). Please mail me/mailing-list any
> > > > issues/suggestions you have.
> > >
> > > It caused Gutsy (2.6.22-14-generic) to crash when I did a swap off of
> > > my hdd swap. I have a GB of ram, so I would have been fine without
> > > ccache.
> >
> > These days "desktops with small memory" probably means virtual
> > machines with, say, <512M RAM :-)
>
> The Hardy liveCD is really snappy with a 192MB VM and and a 128MB
> ccache swap. :)
>

Good to know :)

> > > I had swapped on a 400MB ccache swap.
> > >
> >
> > I need /var/log/messages (or whatever file kernel logs to in Gutsy) to
> > debug this.
> > Please send it to me offline if its too big.
>
> This seems to be the bit you want:
>

Unfortunately none of these messages suggest why crash happened.
If you can send entire log, that will probably be more useful.


> ubuntu-xp syslogd 1.4.1#21ubuntu3: restart.
> Feb 19 08:07:31 ubuntu-xp -- MARK --
> ...
> Feb 19 18:47:31 ubuntu-xp -- MARK --
> Feb 19 18:59:51 ubuntu-xp kernel: [377208.185464] ccache: Unknown
> symbol lzo1x_decompress_safe
<snip>

All these 'Unknown symbol' messages are because you tried loading
ccache.ko module before tlsf.ko and lzo*.ko modules.

>
> > > BTW, why is the default 10% of mem?
> >
> > I have no great justification for "10%".
>
> Perhaps 100% (or maybe 50%) would be a more sensible default? For me
> 66% makes a huge difference to the Hardy liveCD performance. 10% makes
> a difference but 50%+ goes from "ls /" taking 10s to snappy
> performance even on large applications like Firefox.
>

I think this depends a lot on kind of workload and system. For e.g:
- On desktops, retaining too many anonymous pages at cost of
continuously losing page-cache (filesystem-backed) pages can hurt
performance for workload that repeatedly access same file(s).
- On embedded systems, too much de/compression will drain all battery.
and so on...

Also, I don't know which of  these use cases is more "common".

- Nitin

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Re: [linux-mm-cc] Announce: ccache release 0.1

[John McCabe-Dansted]

On Feb 19, 2008 6:39 AM, Nitin Gupta <nitingupta910@gmail.com> wrote:
> Hi All,
>
> I am excited to announce first release of ccache - Compressed RAM
> based swap device for Linux (2.6.x kernel).
>   - Project home: http://code.google.com/p/ccache/
>   - ccache-0.1: http://ccache.googlecode.com/files/ccache-0.1.tar.bz2

I find it counter intuitive that ccache-0.1 is newer than ccache-2.4:
http://ccache.samba.org/

Perhaps you should rename this, perhaps to ccacheM (module).

FYI, ccache still seems solid under Hardy.
A 128MB ccache swap allowed me to easily install from the liveCD on a
VM with only 192MB of ram, rather than the 384MB officially required
for Gutsy.
However I found a funny bug in ubiquity:
  https://bugs.launchpad.net/bugs/193267
  http://www.ucc.asn.au/~mccabedj/ccache/Screenshot-Hardy-fdccache.png
Installing Hardy to /dev/ccache sound like a great idea ;)

I am using a DualCore, with the iso sitting on the harddisk, so a real
low-mem machine could be a lot slower.  however Ubuntu is meant to
require 384MB of memory to install and 256MB of memory to use. It
seems that by adding ccache to the liveCD we could just state a single
figure of 256MB (which is 64MB less than 256MB, so we are giving
ourselves plenty of breathing space for RAM stealing video cards,
unexpected usage spikes etc.)

-- 
John C. McCabe-Dansted
PhD Student
University of Western Australia

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Re: [linux-mm-cc] Announce: ccache release 0.1

[Nitin Gupta]

On Feb 19, 2008 9:46 PM, John McCabe-Dansted <gmatht@gmail.com> wrote:
> On Feb 19, 2008 6:39 AM, Nitin Gupta <nitingupta910@gmail.com> wrote:
> > Hi All,
> >
> > I am excited to announce first release of ccache - Compressed RAM
> > based swap device for Linux (2.6.x kernel).
> >   - Project home: http://code.google.com/p/ccache/
> >   - ccache-0.1: http://ccache.googlecode.com/files/ccache-0.1.tar.bz2
>
> I find it counter intuitive that ccache-0.1 is newer than ccache-2.4:
> http://ccache.samba.org/
>
> Perhaps you should rename this, perhaps to ccacheM (module).
>

My bad. I knew there is going to be confusion with
http://ccache.samba.org/ which has _nothing_ to do with this project.

I am now going to rename this project to "compcache" to avoid any confusion.
New project home will be: http://code.google.com/p/compcache/
It will take few days for this transition to complete.

> FYI, ccache still seems solid under Hardy.
> A 128MB ccache swap allowed me to easily install from the liveCD on a
> VM with only 192MB of ram, rather than the 384MB officially required
> for Gutsy.
> However I found a funny bug in ubiquity:
>   https://bugs.launchpad.net/bugs/193267
>   http://www.ucc.asn.au/~mccabedj/ccache/Screenshot-Hardy-fdccache.png
> Installing Hardy to /dev/ccache sound like a great idea ;)

Yeah. Interesting :)  - /dev/ccache really should not be visible there
since its _not_ possible to install on this device! This is not a
_generic_ block device and can be used only as a swap disk. However, I
am not sure how to make it invisible to installer (maybe load module
after partitioning step is over?).

>
> I am using a DualCore, with the iso sitting on the harddisk, so a real
> low-mem machine could be a lot slower.  however Ubuntu is meant to
> require 384MB of memory to install and 256MB of memory to use. It
> seems that by adding ccache to the liveCD we could just state a single
> figure of 256MB (which is 64MB less than 256MB, so we are giving
> ourselves plenty of breathing space for RAM stealing video cards,
> unexpected usage spikes etc.)
>
>
> --
> John C. McCabe-Dansted
> PhD Student
> University of Western Australia
>

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Re: Announce: ccache release 0.1

[Nitin Gupta]

On Feb 19, 2008 3:09 AM, Nitin Gupta <nitingupta910@gmail.com> wrote:
> Hi All,
>
> I am excited to announce first release of ccache - Compressed RAM
> based swap device for Linux (2.6.x kernel).
>   - Project home: http://code.google.com/p/ccache/
>   - ccache-0.1: http://ccache.googlecode.com/files/ccache-0.1.tar.bz2


This project has now moved to: http://code.google.com/p/compcache/

This was done to avoid confusion with http://ccache.samba.org/ which
has nothing to do with this project.

PS: only user visible change done is that virtual swap device is now
called /dev/compcache

- Nitin

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Re: [linux-mm-cc] Announce: ccache release 0.1

[John McCabe-Dansted]

On Wed, Feb 20, 2008 at 5:12 PM, Nitin Gupta <nitingupta910@gmail.com> wrote:
>  This project has now moved to: http://code.google.com/p/compcache/
>
>  This was done to avoid confusion with http://ccache.samba.org/ which
>
> has nothing to do with this project.
>
>  PS: only user visible change done is that virtual swap device is now
>  called /dev/compcache

You haven't updated the README file, fortunately
   sed s/ccache/compcache/g < README > README.new
 seems to do exactly what you want.

Perhaps for the convenience of your users you could also include
swapon_compcache.sh:

#!/bin/sh
#Ubuntu Hardy does include lzo_compress and lzo_decompress
(modprobe lzo_compress || insmod
./sub-projects/compression/lzo-kmod/lzo1x_compress.ko) &&
(modprobe lzo_decompress || insmod
./sub-projects/compression/lzo-kmod/lzo1x_decompress.ko) &&
insmod ./sub-projects/allocators/tlsf-kmod/tlsf.ko &&
insmod ./compcache.ko &&
#insmod ./compcache.ko compcache_size_kbytes=128000 &&
sleep 1 &&
swapon /dev/compcache
lsmod | grep lzo
lsmod | grep tlsf
lsmod | grep cache

And swapoff_compcache.sh:

#!/bin/sh
swapoff /dev/ccache
swapoff /dev/compcache
rmmod ccache
rmmod compcache
rmmod tlsf
rmmod lzo1x_compress
rmmod lzo_compress
rmmod lzo1x_decompress
rmmod lzo_decompress

-- 
John C. McCabe-Dansted
PhD Student
University of Western Australia

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Re: Announce: ccache release 0.1

[Pekka Enberg]

On Feb 18, 2008 11:39 PM, Nitin Gupta <nitingupta910@gmail.com> wrote:
> Code reviews will be really helpful! :)

Then you should just post the patches to LKML / linux-mm for review.

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Re: [linux-mm-cc] Announce: ccache release 0.1

[Nitin Gupta]

On Feb 20, 2008 1:59 PM, John McCabe-Dansted <gmatht@gmail.com> wrote:
> On Wed, Feb 20, 2008 at 5:12 PM, Nitin Gupta <nitingupta910@gmail.com> wrote:
> >  This project has now moved to: http://code.google.com/p/compcache/
> >
> >  This was done to avoid confusion with http://ccache.samba.org/ which
> >
> > has nothing to do with this project.
> >
> >  PS: only user visible change done is that virtual swap device is now
> >  called /dev/compcache
>
> You haven't updated the README file, fortunately
>    sed s/ccache/compcache/g < README > README.new
>  seems to do exactly what you want.
>

Now compcache download has updated README.

> Perhaps for the convenience of your users you could also include
> swapon_compcache.sh:
>
> #!/bin/sh
> #Ubuntu Hardy does include lzo_compress and lzo_decompress


I wonder why ubuntu renamed lzo1x_compress module to lzo_compress and
likewise for decompressor. Anyway, I will add these scripts to
download.


> (modprobe lzo_compress || insmod
> ./sub-projects/compression/lzo-kmod/lzo1x_compress.ko) &&
> (modprobe lzo_decompress || insmod
> ./sub-projects/compression/lzo-kmod/lzo1x_decompress.ko) &&
> insmod ./sub-projects/allocators/tlsf-kmod/tlsf.ko &&
> insmod ./compcache.ko &&
> #insmod ./compcache.ko compcache_size_kbytes=128000 &&
> sleep 1 &&
> swapon /dev/compcache
> lsmod | grep lzo
> lsmod | grep tlsf
> lsmod | grep cache
>
> And swapoff_compcache.sh:
>
> #!/bin/sh
> swapoff /dev/ccache
> swapoff /dev/compcache
> rmmod ccache
> rmmod compcache
> rmmod tlsf
> rmmod lzo1x_compress
> rmmod lzo_compress
> rmmod lzo1x_decompress
> rmmod lzo_decompress
>
>
> --
> John C. McCabe-Dansted
> PhD Student
> University of Western Australia
>

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