[<prev] [next>] [thread-next>] [day] [month] [year] [list]
Message-ID: <47425EA5.7000607@rtr.ca>
Date: Mon, 19 Nov 2007 23:12:21 -0500
From: Mark Lord <lkml@....ca>
To: Andrew Morton <akpm@...ux-foundation.org>,
Linus Torvalds <torvalds@...l.org>,
Ingo Molnar <mingo@...e.hu>,
Linux Kernel <linux-kernel@...r.kernel.org>
Subject: CONFIG_IRQBALANCE for 64-bit x86 ?
On 32-bit x86, we have CONFIG_IRQBALANCE available,
but not on 64-bit x86. Why not?
I ask, because this feature seems almost essential to obtaining
reasonable latencies during heavy I/O with fast devices.
My 32-bit Core2Duo MythTV box drops audio frames without it,
but works perfectly *with* IRQBALANCE.
My QuadCore box works very well in 32-bit mode with IRQBALANCE,
but responsiveness sucks bigtime when run in 64-bit mode (no IRQBALANCE)
during periods of multiple heavy I/O streams (USB flash drives).
That's with both the 32 and 64 bit versions of Kubuntu Gutsy,
so the software uses pretty much identical versions either way.
As near as I can tell, when IRQBALANCE is not configured,
all I/O device interrupts go to CPU#0.
I don't think our CPU scheduler takes that into account when assigning
tasks to CPUs, so anything sent to CPU0 runs with very high latencies.
Or something like that.
Why no IRQ_BALANCE in 64-bit mode ?
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists