Re: [RFC 4/9] Atomic reclaim: Save irq flags in vmscan.c

[Andi Kleen <andi@firstfloor.org>]

Christoph Lameter <clameter@sgi.com> writes:

> Reclaim can be called with interrupts disabled in atomic reclaim.
> vmscan.c is currently using spinlock_irq(). Switch to spin_lock_irqsave().

I like the idea in principle. If this fully works out we could
potentially keep less memory free by default which would be a good
thing in general: free memory is bad memory.

But would be interesting to measure what the lock
changes do to interrupt latency. Probably nothing good.

A more benign alternative might be to just set a per CPU flag during
these critical sections and then only do atomic reclaim on a local
interrupt when the flag is not set.  That would make it a little less
reliable, but much less intrusive and with some luck still give many
of the benefits.

-Andi

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