Messages in this thread | | | From | Andi Kleen <> | Subject | Re: ext4 performance falloff | Date | Mon, 07 Apr 2014 09:40:28 -0700 |
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Jan Kara <jack@suse.cz> writes: > > What we really need is a counter where we can better estimate counts > accumulated in the percpu part of it. As the counter approaches zero, it's > CPU overhead will have to become that of a single locked variable but when > the value of counter is relatively high, we want it to be fast as the > percpu one. Possibly, each CPU could "reserve" part of the value in the > counter (by just decrementing the total value; how large that part should > be really needs to depend to the total value of the counter and number of > CPUs - in this regard we really differ from classical percpu couters) and > allocate/free using that part. If CPU cannot reserve what it is asked for > anymore, it would go and steal from parts other CPUs have accumulated, > returning them to global pool until it can satisfy the allocation.
That's a percpu_counter() isn't it? (or cookie jar)
The MM uses similar techniques.
-Andi
-- ak@linux.intel.com -- Speaking for myself only
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