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Date:      Mon, 8 Apr 2013 17:14:59 +0000
From:      "Duvvuru,Venkat Kumar" <VenkatKumar.Duvvuru@Emulex.Com>
To:        "freebsd-net@freebsd.org" <freebsd-net@freebsd.org>
Subject:   drbr_enqueue - OCE driver - Freebsd 9.1
Message-ID:  <BF3270C86E8B1349A26C34E4EC1C44CB2B82015D@CMEXMB1.ad.emulex.com>
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Hi,
In the transmit path, if enqueue mechanism is used instead of blocking on the lock, the throughput is not good in some scenarios (especially single queue, multiple connections).
For example:
if (TRY_LOCK(&wq->tx_lock)) {
           status = oce_multiq_transmit(ifp, m, wq);
           UNLOCK(&wq->tx_lock);
     } else {
           status = drbr_enqueue(ifp, wq->br, m);
     }

Instead of the above code where the request is enqueued if I use a normal LOCK and block on it, it is giving good performance.

Any suggestions on why the throughput is low in case of enqueue mechanism.

Thx,
Venkat.

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