Group,
This example is done with a single threaded app.
It is NOT NOT NOT intended to show any level of
Thread-safe type coding.
It is ONLY used to show that it is signifcantly lower cost
to grab pre-allocated objects than to allocate the
objects on demand.
Thus, grabbing 64 byte chunks off a free list and
placing them back on can be done with this simple
base code even when dealing with 1Gb/sec intfs.
Under extreme circumstances, the normal on demand
allocator can sleep if it needs to colesce memory
or steal it from another's cache.
Mitchell Erblich
-----------------
Frank Hofmann wrote:
>
> On Thu, 5 Oct 2006, Erblichs wrote:
>
> > Casper Dik,
> >
> > After my posting, I assumed that a code question should be
> > directed to the ZFS code alias, so I apologize to the people
> > show don't read code. However, since the discussion is here,
> > I will post a code proof here. Just use "time program" to get
> > a generic time frame. It is under 0.1 secs for 500k loops
> > (each loop does removes a obj and puts it back).
> >
> > It is just to be used as a proof of concept that a simple
> > pre-alloc'ed set of objects can be accessed so much faster
> > than allocating and assigning them.
>
> Ok, could you please explain how is this piece (and all else, for that
> matter):
>
> /*
> * Get a node structure from the freelist
> */
> struct node *
> node_getnode()
> {
> struct node *node;
>
> if ((node = nodefree) == NULL) /* "shouldn't happen" */
> printf("out of nodes");
>
> nodefree = node->node_next;
> node->node_next = NULL;
>
> return (node);
> }
>
> is multithread-safe ?
>
> Best wishes,
> FrankH.
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