Re: [PATCH] Remove MemPools use of calloc()

On 01/11/2013 12:34 AM, Amos Jeffries wrote:

> MemPools contains a doZeroOnPush flag to optimize performance by
> removing use of memset() as chunks are added back into the pool.

yes, although to avoid misunderstanding I would phrase it differently:
"If doZeroOnPush is true, the pool zeros chunks added back into the pool".

> However, on closer inspection it is clear that the following pop()
> process to re-use those chunks is never performing memset() anyway.

Here, I assume you are talking about pools which have zeroOnPush set to
false.

> As
> such I believe that there is no special need to use calloc() on these
> particular object types in the first place.
>
> The attached patch updates MemPools to use malloc() instead of calloc()
> on all types with doZeroOnPush set.

Yes, if "set" means "set to false" :-)

> This should increase performance a
> little, and allows us to remove the anti-pattern by setting doZeroOnPush
> for more objects as we can verify they are correctly initialized by
> their constructors.

Again, I assume "setting doZeroOnPush" means "setting doZeroOnPush to
false". In your commit message, please use a less misleading terminology.

Please rename doZeroOnPush and friends to doZero or at least document
that member to indicate that it affects both allocated and pushed data now.

While you are documenting, it may be a good idea to explain that we zero
on push because we are afraid of broken code using stale/dirty data
after the memory was returned to the pool. If we were not afraid of
that, we would zero on allocate() instead!

Thank you,

Alex.
Received on Sat Jan 12 2013 - 17:52:03 MST