Daniel Phillips <[EMAIL PROTECTED]> :
[...]
> A point on memory pressure: here, we are not talking about the continuous
> state of running under heavy load, but rather the microscopically short
> periods where not a single page of memory is available to normal tasks. It
> is when a block IO event happens to land inside one of those microscopically
> short periods that we run into problems.
You suggested in a previous message to use an emergency allocation pool at
the driver level. Afaik, 1) the usual network driver can already buffer a
bit with its Rx descriptor ring and 2) it more or less tries to refill it
each time napi issues its ->poll() method. So it makes me wonder:
- have you collected evidence that the drivers actually run out of memory
in the (microscopical) situation you describe ?
- instead of modifying each and every driver to be vm aware, why don't
you hook in net_rx_action() when memory starts to be low ?
Btw I do not get what the mempool/GFP_CRITICAL idea buys: it seems redundant
with the threshold ("if (memory_pressure)") used in the Rx path to decide
that memory is low.
--
Ueimor
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