[linux-mm-cc] Re: Some testings using ccache pre-alpha 003 for i386

[Anderson Briglia]

Hi all,

I did a quick test with the pre-alpha 004 and fillmem. Using a larger
ccache, we can improve the test's speed. (see file attached). This
version seems to be more stable and "workable" on a real environment.
:-)
Actually we need a testing use case that is able to show the ccache
benefits with anon pages.
AFAIK, this ccache version was designed to improve the memory
consumption, postponing the OOM killer call, for instance. So, we need
a test use case that evaluates this.

Best regards,

Anderson Briglia


On 8/28/06, Nitin Gupta <nitingupta.mail at gmail.com> wrote:
> Hi,
>
> Please see new page posted on project home page:
> http://linuxcompressed.sourceforge.net/braindumps
> I have detailed here possible explanation for these negative results.
>
> I hope to have some solutions implemented soon :)
>
> Cheers,
> Nitin
>
>
> Anderson Briglia wrote:
> > Hi all,
> >
> > I did some tests using the latest ccache code posted by Nitin Gupta. I
> > divided the tests in two types: Memory behavior and time performance.
> > All tests had this scenario:
> >
> > - linus kernel 2.6.18-rc4 with ccache pre-alpha 003 applied
> > - qemu with ubuntu-dapper image
> > - 128MB of RAM
> > - No Swap devices
> > - After every test, the machine was rebooted
> >
> > Memory Behavior
> > -----------------------------------------------------------
> > This test intends to evaluate what happens on the system when it has a
> > high memory load. What is the ccache impact? Is it stable even the
> > free memory is critical low?
> > To do this test I used memtest 0.0.4 [1], that is a suite of tests
> > developed to evaluate the stability and consistency of the Linux
> > memory management system. It is composed of some testing programs but
> > I used just one test, called fillmem. Fillmem tests the memory
> > allocation system. It is useful to check the virtual memory system
> > face allocation memory, pagination and swap usage. As its parameter,
> > fillmem receives the size of the memory that will be allocated.
> >
> > fillmem50-ccache1000.gif (graph01) attached file represents the memory
> > when executed fillmem with 50MB of parameter and ccache with 1000
> > pages of size.
> > fillmem50-no-ccache.gif (graph02) attached file represents the memory
> > when executed fillmem with 50MB as well, but without ccache.
> > The x axis represents the time in seconds and the y axis the memory in
> > kilobytes. Make a comparison between the two graphs, we can see that
> > the ccache adds a overhead because the test spends more time to
> > allocate and free the same memory size. And we have also the number of
> > AnonPages increased. Maybe due the metadata needed for the ccache
> > control.
> > One more thing is, 1000 pages as ccache size are not enough to improve
> > the memory allocation. I didn't use a bigger ccache size because it's
> > not stable yet and the system just freezes if the ccache is bigger (>
> > 10MB for example). Discussing with Nitin, he said me that it's
> > something related to the LRU active list handling. He is investigating
> > this problem.
> >
> > Time Performance
> > --------------------------------------------------------
> > This test intends to evaluate the ccache overhead when executing the
> > memory test and an application. I selected the Firefox startup to
> > measure. Just called firefox at the command line with 'time' to do the
> > measurements. The same way was used to measure the time when executing
> > the fillmem test.
> >
> > fillmem-test-time.gif attached file represents the time measurement
> > when executing the fillmem test discussed above. As you can see, the
> > test is much more faster (almost 3 times) without ccache. I believe it
> > is expected once we naturally have an overhead to use the ccache
> > system: all those chunk's operations, vswap control, etc...
> >
> > firefox-startup[01-02].gif attached files represent the time spent to
> > load firefox. On this test, I executed firefox two times without
> > reboot the machine. I was expecting a gain on the speed when using
> > ccache, once we should have more 'firefox anonpages' in the memory
> > when using ccache. But as we can see, we don't have a big difference
> > when using and not using the ccache. But the startup was faster when
> > ccache was used.
> >
> > Conclusion
> > ------------------------------------------------------
> > I believe that it's early to take some conclusion of the ccache
> > benefits. More use cases must be developed and tested to check the
> > impact and improvements of it. We just have a pre-alpha version and we
> > have to focus on fix the bugs to have a 'real workable' ccache
> > version.
> >
> > References
> > -----------------------------------------------------
> > [1] Memtest Suite. <http://carpanta.dc.fi.udc.es/~quintela/memtest/>
> >
> >
> > Best regards,
> >
> > Anderson Briglia
> > Open Source Mobile Research Center - Embedded Linux Lab
> > Instituto Nokia de Tecnologia - INdT - Manaus/Brazil
> >
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>
>
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