On 9-Apr-09, at 3:36 PM, Andi Kleen wrote:
Using a mutex seems like the sane choice here. I'd advocate spinlocks
for a new filesystem any day (but even there it's a fine choice to
have
a mutex, if top of the line scalability is not an issue).
But for a legacy filesystem like reiser3, which depended on the BKL
reiser3 is much more widely used in the user base than a lot of "non
legacy" file systems. It's very likely it has significantly
more users than ext4 for example. Remember that it was the default
file system
for a major distribution until very recently.
... and based on track record probably still should be :/
--Toby
(Who has no idea why good solid code that works really well magically
gets labelled 'legacy' and shelved in favour of flaky, immature code.)
I also got a few
reiser3 fs still around, it tended to perform very well
on kernel hacker workloads.
Given all that I think the current performance penalties Frederic
reports
are not acceptable. Dropping BKL is not a cause in itself, but should
just improve performance.
auto-dropping on schedule() it would be rather fragile to use
spinlocks,
and it would take forever to validate the result.
Not convinced it would be that hard. It could be probably done with
some
straight forward static code analysis. And after that since there's
not much development going anymore it's unlikely to break again.
-Andi
--
ak@xxxxxxxxxxxxxxx -- Speaking for myself only.
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