On 31/08/18 20:10, Emil Velikov wrote:
Hi Timothy,
On 31 August 2018 at 10:57, Timothy Arceri <tarc...@itsqueeze.com> wrote:
On 31/08/18 19:40, Bas Nieuwenhuizen wrote:
+TImothy
On Fri, Aug 31, 2018 at 11:32 AM Alexander Larsson <al...@redhat.com>
wrote:
Hi, I'm the developer behind flatpak (https://flatpak.org/) and we've
recently run into some issues with the mesa shader cache. Flatpak has
a app/runtime split where the runtime is shared between app and
provides /usr. The runtime contains a version of mesa, but this can be
overridden by runtime extensions to add other OpenGL drivers.
Each app has a separate $XDG_CACHE_HOME, pointing into the per-app
writable storage. For example, gedit has
XDG_CACHE_HOME="/home/alex/.var/app/org.gnome.gedit/cache". This
causes mesa to store the shader cache per-app in
$XDG_CACHE_HOME/mesa_shader_cache.
In the regular case this works fine, but sometimes the version of mesa
is changed, with the shader cache being left in place. For example,
sometimes we update the mesa version in the runtime, and sometimes the
app switches to a new runtime which has a different mesa version.
Such updates have caused a lot of issues for us, ranging from direct
crashes at startup as in
https://github.com/flatpak/flatpak/issues/2052 and sometimes just
super-slow performance. In all cases, blowing away the shader cache
directory fixed all issues.
The steam flatpak has a bunch of workaround for the cache:
https://github.com/flathub/com.valvesoftware.Steam/blob/master/steam_wrapper/steam_wrapper.py#L35
But we can't expect every app to do this.
So, my question is, is the cache supposed to be backward compatible,
or at least versioned? Are we missing something in our mesa builds to
make that work? Is this fixed somewhere with a patch i can backport?
And if not, do we need to add some magic to flatpak to automatically
clean up the shader cache after an update?
It is supposed to be versioned automatically by mesa.
Hi Alexander,
We depend on build timestamps of the mesa/llvm binaries when generating the
sha for cache items. So if flatpak results in two versions of mesa having
the same timestamp then there is likely going to be issues.
static inline bool
disk_cache_get_function_timestamp(void *ptr, uint32_t* timestamp)
{
Dl_info info;
struct stat st;
if (!dladdr(ptr, &info) || !info.dli_fname) {
return false;
}
if (stat(info.dli_fname, &st)) {
return false;
}
*timestamp = st.st_mtime;
return true;
}
Have you tried using the build-id from src/util/build_id.c?
Hi Emil,
Honestly I've got no idea what that code does. Maybe someone who does
could write patches to switch to it along with an explanation of why its
better. Even just adding some comments in that file would be helpful.
I don't want to be the one responsible for it (and any new issues with
the cache) when I'm not aware of how it works :(
Tim
The reproducible builds' date/time override feature, is something
people could easily misusing.
Effectively having the same timestamp across multiple, completely
different, builds.
HTH
Emil
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