Re: [Libreoffice] ccache support

On Fri, 2011-09-09 at 20:22 +0200, Lubos Lunak wrote:
> On Friday 09 of September 2011, Norbert Thiebaud wrote:
>
>  Could somebody else, preferably with a somewhat more common system :), post 
> their results, so that we can compare? I assume the ccache overhead (caused 
> by I/O I'd say) is exceptionally high here, but I still doubt ccache warrants 
> being enabled by default just like that.
>
> > I don't do that in configure for the same reason we don't change
> > CCACHE_DIR or the cache dir size.
> > Using ccache if available is one thing... but trying to
> > 'auto-magically' optimize ccache is another can of worms altogether...
>
>  I think the case above shows that there are some worms even in the one thing.

Well, let me throw some more numbers on the pile, about
space, number of cached files, and hits.  Short version:
cache compression reduces cache size by very roughly a
factor of 5.

My RAM is so small, at 512MB, that I omit timings; besides I
kept using the system for other things at the same time.
All compiles yesterday were with cache compression turned on.

"Size" is in KB as reported by `du --summarize ~/.ccache`.
Files, hits, and misses are from `ccache -s`.

I started yesterday with a cache holding files from a number
of previous builds of LibreOffice, some of them compressed,
but lots not (just because I keep forgetting to set
CCACHE_COMPRESS; yes, I have now added that to my .bashrc):
    size   : 9563228
    files  : 79453
    hits   : 54662 + 510
    misses : 39198
I calculate average file size 120.02KB

After some unsuccessful attempts to rebuild:
    size   : 9618256
    files  : 81585
    hits   : 54874 + 629
    misses : 39990
I calculate average file size 117.85KB and average size
21.03KB for the 2184 new files.

After successful complete build, which cleaned out part of
the cache:
    size   : 9123940
    files  : 99112
    hits   : 62377 + 3080
    misses : 48614
I calculate average file size 92.06KB.

FWIW, and HTH
Terry.