Christoph Lameter a écrit :
On Tue, 13 Dec 2005, Eric Dumazet wrote:
Say you move to read mostly most of struct kmem_cache *, they are guaranteed
to stay in 'mostly read'.
True but then this variable is not frequently read. So false sharing would
not have much of an impact.
If this variable is not frequently used, why then define its own cache ?
Ie why not use kmalloc() and let kernel use a general cache ?
On a 32 CPUS machine, a kmem_create() costs a *lot* of ram.
This overhead is acceptable if and only if :
- A lot of objects can be allocated in some cases (and using a special cache
can save ram because of power of two general caches alignement)
- A lot of objects are created/deleted per unit of time (performance is critical)
For example pipe() could use its own cache to speedup some benchmarks, but the
general kmalloc()/kfree() was chosen instead.
Eric
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