On 04/05/2012 03:42 PM, Saggi Mizrahi wrote:
> The performance implication though existing don't really pop up in
> normal use.

In a previous life I worked on a product that logged a *ton* to multiple
circular in memory binary buffers (memory was preserved on reset and
written to flash when the system booted to allow later retrieval aka.
flight recorder).  It was optimized to minimize run-time costs (~10us to
log a message).  This was done so that you never had to re-create a
failure.  No one believed that it would effect performance that much,
but one of the folks profiled it and found logging was eating at least
10% of the total CPU (embedded system).

> It's true we usually don't need logs that far back but as I said it's
> really not an issue. Even when you try and run a 1000 VMs you will
> not be blocked on logging trying to get written to disk I can assure
> you of that.

Has anyone gathered the data that shows what the logging costs when you
have *many* VMs?  Even a small operation can become relevant when you
have sufficiently large numbers of them.

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