Date: Sat, 10 Aug 2002 11:47:09 -0700 From: Terry Lambert <tlambert2@mindspring.com> To: Bruce Evans <bde@zeta.org.au> Cc: Maksim Yevmenkin <myevmenk@exodus.net>, current@FreeBSD.ORG Subject: Re: Interrupt vs. polling on -current Message-ID: <3D555FAD.A4137491@mindspring.com> References: <20020810192039.E16346-100000@gamplex.bde.org>
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Bruce Evans wrote: > No, but the 3Com driver apparently is. The sio driver wants to have > fast interrupts. It can't have them with the irq is shared, so its > worst-case interrupt latency for a single serial port is increased > from about 50 usec to many msec, depending other interrupt activity > in the system (not limited to that for the shared irq except in some > configurations). Silo overflows occur at 115200 bps when the latency > is more than about 1.5 msec. Anyway to get the code to complain about the sharing of serial interrupts? Also, if there is a PCI interrupt for the serial (serial handled by Northbridge... I'd like to see this, actually), shouldn't it be capable of sharing *only* fast interrupts somehow? It's an obvious pessimization to mix other interrupts with fast interrupts, but less obvious what would happen with fast + fast... > FreeBSD on a 486/33 can handle about 40000 serial interrupts per second > to do one character of i/o per interrupt). Pessimizations in -current > have only degraded this by a small factor (2?), provided the driver > uses fast interrupts. Lose another small factor (2?) for normal interrupts > (using normal interrupts only loses a large factor for latency). Any way to fix this, short of "don't run -current"?? Thanks, -- Terry To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message
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