Re: [OE-core] [PATCH] sstate: allow marking a cached object as in use without touching mtime

[Richard Purdie <richard.purdie@linuxfoundation.org>]

On Wed, 2026-09-09 at 23:22 +0200, Michael Haener via lists.openembedded.org wrote:
> Every access to an object in the sstate cache is recorded with a plain
> touch, which writes both the modification time and the access time.
> 
> Add SSTATE_ATIME_UPDATE_AFTER. When it is set, the modification time is no
> longer written, and the access time is refreshed only once the existing
> one is at least that many seconds old.
> 
> This reduces the number of write cycles a build causes on the cache, which
> matters most where many build servers share one sstate cache: each of them
> would otherwise refresh the access time of every object it looks at.
> 
> With mtime and atime kept apart, a cache can also be measured for reuse
> and age.
> 
> When the variable is unset the behaviour is unchanged.
> 
> Signed-off-by: Michael Haener <michael.haener@siemens.com>
> Reviewed-by: Adrian Freihofer <adrian.freihofer@siemens.com>
> Reviewed-by: Peter Marko <peter.marko@siemens.com>
> ---
>  meta/classes-global/sstate.bbclass | 59 ++++++++++++++++++++++--------
>  1 file changed, 43 insertions(+), 16 deletions(-)

Whilst I can understand the motivation, I can't say I'm thrilled by
complicating this code again. I'd recently tried to simplify it as the
different access patterns were causing various problems in their own
right. This adds a new variable, two implementations (shell and python)
of an algorithm and it just makes the code more complex and hard to
understand.

Cheers,

Richard