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Date: Wed, 3 Jan 2007 21:33:24 +0200 From: "Michael S. Tsirkin" <mst@...lanox.co.il> To: Steve Wise <swise@...ngridcomputing.com> Cc: netdev@...r.kernel.org, Roland Dreier <rdreier@...co.com>, linux-kernel@...r.kernel.org, openib-general@...nib.org Subject: Re: [PATCH v4 01/13] Linux RDMA Core Changes > Without extra param (1000 iterations in cycles): > ave 101.283 min 91 max 247 > With extra param (1000 iterations in cycles): > ave 103.311 min 91 max 221 A 2% hit then. Not huge, but 0 either. > Convert cycles to ns (3466.727 MHz CPU): > > Without: 101.283 / 3466.727 = .02922us == 29.22ns > With: 103.311 / 3466.727 = .02980us == 29.80ns > > So I measure a .58ns average increase for passing in the additional > parameter. That depends on CPU speed though. Percentage is likely to be more universal. > Here is a snipit of the test: > > spin_lock_irq(&lock); > do_gettimeofday(&start_tv); > for (i=0; i<1000; i++) { > cycles_start[i] = get_cycles(); > ib_req_notify_cq(cb->cq, IB_CQ_NEXT_COMP); > cycles_stop[i] = get_cycles(); > } > do_gettimeofday(&stop_tv); > spin_unlock_irq(&lock); > > if (stop_tv.tv_usec < start_tv.tv_usec) { > stop_tv.tv_usec += 1000000; > stop_tv.tv_sec -= 1; > } > > for (i=0; i < 1000; i++) { > cycles_t v = cycles_stop[i] - cycles_start[i]; > sum += v; > if (v > max) > max = v; > if (min == 0 || v < min) > min = v; > } > > printk(KERN_ERR PFX "FOO delta sec %lu usec %lu sum %llu min %llu max %llu\n", > stop_tv.tv_sec - start_tv.tv_sec, > stop_tv.tv_usec - start_tv.tv_usec, > (unsigned long long)sum, (unsigned long long)min, > (unsigned long long)max); Good job, the test looks good, thanks. So what does this tell you? To me it looks like there's a measurable speed difference, and so we should find a way (e.g. what I proposed) to enable chelsio userspace without adding overhead to other low level drivers or indeed chelsio kernel level code. What do you think? Roland? -- MST - To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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