Hello,
When working on the problem that resulted in commit
https://github.com/zfsonlinux/zfs/commit/5d862cb0d9a4b6dcc97a88fa0d5a7a717566e5ab
in ZoL, I got the impression this problem would affect the rest of the
OpenZFS community. I'm posting this note to ask others to check whether
their implementation should get this patch.
On another note, and one that possibly impacts SA management as well as
other things, I'm curious whether anyone in the OpenZFS community has
experienced problems as various OS distros have adopted gcc 4.8. I
realize that FreeBSD uses a much older version and I've got no idea
about Illumos. I'd like to refer the community to
https://github.com/zfsonlinux/zfs/commit/5d862cb0d9a4b6dcc97a88fa0d5a7a717566e5ab
which is a rather absurd hack for ZoL to deal with problems caused by
gcc 4.8's "aggressive loop optimization". Briefly, the compiler will
over-optimize loops in some cases where a typical array index iterator
is used. The troublemaker in ZFS is the dn_blkptr[] array. See the
referenced commit for the particular bug it caused. I'm pointing this
out as a potential issue as gcc 4.8 becomes more widespread (and,
possibly applicable to clang/llvm, too).
- Tim
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