Re: CCACHE_READONLY=1 setting now working

Thanks for the quick response, Joel.

>> It's true that ccache still performs some write operations in read-only
mode: it updates statistics counters and updates mtime of files in the
cache in case there was a cache hit
>> Thus, read-only mode should be interpreted as "will not add new
compilation results to the cache", not "will not perform any write
operations to the cache".

That explains. I am ok with this behavior.

>> If ccache can't perform those updates due to lack of permission, it just
continues with life silently
>> From your question, I assume that this behavior is not what you expected
or wanted. Is it a problem in your case that ccache performs those write
operations? Or have you found a case where ccache in read-only mode
actually writes the result of a compilation into the cache?

We have a continuous integration setup which updates the ccache and we want
everyone else just to consume the ccache.  I was a little worried that the
result of compilation was being written back to the ccache and seems thats
not the case. However, the time taken for the build when CCACHE_READONLY=1
flag is set is much more compared to the time taken when this flag is not
set. The ccache hit rate is almost the same in both cases. I am using
CCACHE_TEMPDIR option ( same filesystem location ) with CCACHE_READONLY
flag. Could you let me know what could have gone wrong in this setup ?

Thanks,
Dinesh G


On Fri, Feb 20, 2015 at 12:09 PM, Joel Rosdahl <[email protected]> wrote:

> Hi Dinesh,
>
> > I am using ccacge version 3.1.9 and trying a build with CCACHE_READONLY=1
> > and it seems not to be working. It tries to write back to the ccache.
> [...]
>
> The problem mentioned in the mail to which you refer was that ccache tried
> to create subdirectories in the cache and exited with a fatal error if it
> couldn't create them, even when running in read-only mode. That was fixed
> in 3.1.9.
>
> It's true that ccache still performs some write operations in read-only
> mode: it updates statistics counters and updates mtime of files in the
> cache in case there was a cache hit (this is to be able to tell which files
> can be removed when the max cache size limit is reached). If ccache can't
> perform those updates due to lack of permission, it just continues with
> life silently. Thus, read-only mode should be interpreted as "will not add
> new compilation results to the cache", not "will not perform any write
> operations to the cache".
>
> From your question, I assume that this behavior is not what you expected
> or wanted. Is it a problem in your case that ccache performs those write
> operations? Or have you found a case where ccache in read-only mode
> actually writes the result of a compilation into the cache?
>
> -- Joel
>