Date: Tue, 2 Aug 2005 15:37:26 +0300 From: Victor Semionov <victor@vmpbg.com> To: freebsd-questions@freebsd.org Subject: polling decreases throughput ~50% Message-ID: <200508021537.26986.victor@vmpbg.com>
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Hello, I've noticed something that seems strange to me and I'd like to ask for an explanation, because I don't think it should be happening. I was uploading some large file to my neighbor's windows box. With polling disabled, the transfer rate was 8 MB/s and CPU usage was 90%. I turned on polling with sysctl and CPU usage decreased to 50%, which I expected, but also the transfer rate dropped to 4.5 MB/s, about half. The numbers are approximate. The interface is a RealTek (rl driver). No background jobs were running. kern.polling.* all defaults. Why is that? I thought polling should decrease CPU usage by avoiding too many context switches when a hw irq is generated frequently, but it shouldn't make the transfer slower if there are no other jobs running. Thanks
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