From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1161066AbcE3Alz (ORCPT ); Sun, 29 May 2016 20:41:55 -0400 Received: from relmlor3.renesas.com ([210.160.252.173]:29815 "EHLO relmlie2.idc.renesas.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1161015AbcE3Alx (ORCPT ); Sun, 29 May 2016 20:41:53 -0400 X-IronPort-AV: E=Sophos;i="5.22,559,1449500400"; d="scan'";a="212318293" Authentication-Results: intel.com; dkim=none (message not signed) header.d=none;intel.com; dmarc=none action=none header.from=renesas.com; Message-ID: <877fecbcxh.wl%kuninori.morimoto.gx@renesas.com> From: Kuninori Morimoto Subject: [PATCH v2] dma: rcar-dmac: use list_add() on rcar_dmac_desc_put() User-Agent: Wanderlust/2.15.9 Emacs/24.3 Mule/6.0 To: Vinod Koul , Geert Uytterhoeven , Laurent Pinchart CC: , sakato , , OSD2 ML In-Reply-To: <1645988.6VIRltF7C5@avalon> References: <8760w7xq3n.wl%kuninori.morimoto.gx@renesas.com> <874mbrxnft.wl%kuninori.morimoto.gx@renesas.com> <1645988.6VIRltF7C5@avalon> MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") Content-Type: text/plain; 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Descriptors themselves are preallocated, and allocation of the chunks and buffer is performed the first time the descriptor is used. The memory isn't freed when the transfer is completed, as the chunks and buffer will be needed again when the descriptor is reused internally, so the driver keeps the memory around. If only a few descriptors are used concurrently, the current list_add_tail() implementation will result in all preallocated descriptors being used before going back to the first one, and will thus allocate chunks and a buffer for all preallocated descriptors. Using list_add() will put the complete descriptor at the head of the list of available descriptors, so the next transfer will be more likely to reuse a descriptor that already has associated memory instead of one that has never been used before. Signed-off-by: Kuninori Morimoto --- v1 -> v2 - used Laurent's explain on log drivers/dma/sh/rcar-dmac.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/dma/sh/rcar-dmac.c b/drivers/dma/sh/rcar-dmac.c index 02b86c6..616c63a 100644 --- a/drivers/dma/sh/rcar-dmac.c +++ b/drivers/dma/sh/rcar-dmac.c @@ -519,7 +519,7 @@ static void rcar_dmac_desc_put(struct rcar_dmac_chan *chan, spin_lock_irqsave(&chan->lock, flags); list_splice_tail_init(&desc->chunks, &chan->desc.chunks_free); - list_add_tail(&desc->node, &chan->desc.free); + list_add(&desc->node, &chan->desc.free); spin_unlock_irqrestore(&chan->lock, flags); } -- 1.9.1