Re: [RFC][PATCH 1/7] Resource counters

Herbert Poetzl <herbert@xxxxxxxxxxxx> writes:


Linux-VServer does the accounting with atomic counters,
so that works quite fine, just do the checks at the
beginning of whatever resource allocation and the
accounting once the resource is acquired ...

Atomic operations versus locks is only a granularity thing.
You still need the cache line which is the cost on SMP.

Are you using atomic_add_return or atomic_add_unless or
are you performing you actions in two separate steps which
is racy? What I have seen indicates you are using a racy two separate
operation form.

If we'll remove failcnt this would look like
while (atomic_cmpxchg(...))
which is also not that good.

Moreover - in RSS accounting patches I perform page list
manipulations under this lock, so this also saves one atomic op.

it still hasn't been shown that this kind of RSS limit
doesn't add big time overhead to normal operations
(inside and outside of such a resource container)

note that the 'usual' memory accounting is much more
lightweight and serves similar purposes ...

Perhaps....

Eric
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