linux-kernel - RE: [PATCH] hv_sock: perf: loop in send() to maximize bandwidth

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Date:   Sun, 19 May 2019 19:30:07 +0000
From:   Dexuan Cui <decui@...rosoft.com>
To:     Sunil Muthuswamy <sunilmut@...rosoft.com>,
        KY Srinivasan <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        Sasha Levin <sashal@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Michael Kelley <mikelley@...rosoft.com>
CC:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] hv_sock: perf: loop in send() to maximize bandwidth

> From: Sunil Muthuswamy <sunilmut@...rosoft.com>
> Sent: Thursday, May 16, 2019 7:05 PM
> Currently, the hv_sock send() iterates once over the buffer, puts data into
> the VMBUS channel and returns. It doesn't maximize on the case when there
> is a simultaneous reader draining data from the channel. In such a case,
> the send() can maximize the bandwidth (and consequently minimize the cpu
> cycles) by iterating until the channel is found to be full.
>  ...
> Observation:
> 1. The avg throughput doesn't really change much with this change for this
> scenario. This is most probably because the bottleneck on throughput is
> somewhere else.
> 2. The average system (or kernel) cpu time goes down by 10%+ with this
> change, for the same amount of data transfer.
> 
> Signed-off-by: Sunil Muthuswamy <sunilmut@...rosoft.com>

Reviewed-by: Dexuan Cui <decui@...rosoft.com>

The patch looks good. Thanks, Sunil!

Thanks,
-- Dexuan