Evgeniy Polyakov, on 12/24/2008 05:44 PM wrote:
On Wed, Dec 24, 2008 at 05:37:51PM +0300, Vladislav Bolkhovitin (vst@xxxxxxxx) wrote:
Yes, it is simpler and cleaner, but it requires additional allocation.
This is additional (and quite noticeble) overhead.
Not necessary requires. For instance, in iscsi-scst sk_transaction_token
can (and should) be part of iSCSI cmd structure, so no additional
allocations would be needed.
This is special case, I'm not sure it is always possible to cache that
token and attach to every skb, but if it can be done, then of course
this does not end up with additional overhead.
I think in most cases there would be possibility to embed
sk_transaction_token to some higher level structure. E.g. Xen apparently
should have something to track packets passed through host/guest
boundary. From other side, kmem cache is too well polished to have much
overhead. I doubt, you would even notice it in this application. In most
cases allocation of such small object in it using SLUB is just about the
same as a list_del() under disabled IRQs.
Vlad
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