From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ben Hutchings Subject: [PATCH net-next 3/5] ethtool: Correct description of 'max_coalesced_frames' fields Date: Tue, 16 Aug 2011 01:07:47 +0100 Message-ID: <1313453267.2731.59.camel@bwh-desktop> References: <1313453180.2731.57.camel@bwh-desktop> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org, Eli Cohen To: David Miller Return-path: Received: from exchange.solarflare.com ([216.237.3.220]:41139 "EHLO exchange.solarflare.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751351Ab1HPAHu (ORCPT ); Mon, 15 Aug 2011 20:07:50 -0400 In-Reply-To: <1313453180.2731.57.camel@bwh-desktop> Sender: netdev-owner@vger.kernel.org List-ID: The current descriptions state that these fields specify 'How many packets to delay ... after a packet ...' which implies that the hardware should wait for (max_coalesced_frames + 1) completions before generating an interrupt. It is also stated that setting both this field and the corresponding 'coalesce_usecs' field to 0 is invalid. Together, this implies that the hardware must always be configured to delay a completion IRQ for at least 1 usec or 1 more completion. I believe that the addition of 1 is not intended, and David Miller confirms that the original implementation (in tg3) does not do this. Clarify the descriptions of these fields to avoid this interpretation. Signed-off-by: Ben Hutchings --- include/linux/ethtool.h | 26 +++++++++++++------------- 1 files changed, 13 insertions(+), 13 deletions(-) diff --git a/include/linux/ethtool.h b/include/linux/ethtool.h index 71d45a1..18059ca 100644 --- a/include/linux/ethtool.h +++ b/include/linux/ethtool.h @@ -122,8 +122,8 @@ struct ethtool_eeprom { * @cmd: ETHTOOL_{G,S}COALESCE * @rx_coalesce_usecs: How many usecs to delay an RX interrupt after * a packet arrives. If 0, only @rx_max_coalesced_frames is used. - * @rx_max_coalesced_frames: How many packets to delay an RX interrupt - * after a packet arrives. If 0, only @rx_coalesce_usecs is used. + * @rx_max_coalesced_frames: Maximum number of packets to receive + * before an RX interrupt. If 0, only @rx_coalesce_usecs is used. * @rx_coalesce_usecs_irq: Same as @rx_coalesce_usecs, except that * this value applies while an IRQ is being serviced by the host. * @rx_max_coalesced_frames_irq: Same as @rx_max_coalesced_frames, @@ -132,9 +132,9 @@ struct ethtool_eeprom { * @tx_coalesce_usecs: How many usecs to delay a TX interrupt after * a packet is sent. If 0, only @tx_max_coalesced_frames * is used. - * @tx_max_coalesced_frames: How many packets to delay a TX interrupt - * after a packet is sent. If 0, only @tx_coalesce_usecs is - * used. + * @tx_max_coalesced_frames: Maximum number of packets to be sent + * before a TX interrupt. If 0, only @tx_coalesce_usecs is + * used. * @tx_coalesce_usecs_irq: Same as @tx_coalesce_usecs, except that * this value applies while an IRQ is being serviced by the host. * @tx_max_coalesced_frames_irq: Same as @tx_max_coalesced_frames, @@ -149,21 +149,21 @@ struct ethtool_eeprom { * @pkt_rate_low: Threshold for low packet rate (packets per second). * @rx_coalesce_usecs_low: How many usecs to delay an RX interrupt after * a packet arrives, when the packet rate is below @pkt_rate_low. - * @rx_max_coalesced_frames_low: How many packets to delay an RX interrupt - * after a packet arrives, when the packet rate is below @pkt_rate_low. + * @rx_max_coalesced_frames_low: Maximum number of packets to be received + * before an RX interrupt, when the packet rate is below @pkt_rate_low. * @tx_coalesce_usecs_low: How many usecs to delay a TX interrupt after * a packet is sent, when the packet rate is below @pkt_rate_low. - * @tx_max_coalesced_frames_low: How many packets to delay a TX interrupt - * after a packet is sent, when the packet rate is below @pkt_rate_low. + * @tx_max_coalesced_frames_low: Maximum nuumber of packets to be sent before + * a TX interrupt, when the packet rate is below @pkt_rate_low. * @pkt_rate_high: Threshold for high packet rate (packets per second). * @rx_coalesce_usecs_high: How many usecs to delay an RX interrupt after * a packet arrives, when the packet rate is above @pkt_rate_high. - * @rx_max_coalesced_frames_high: How many packets to delay an RX interrupt - * after a packet arrives, when the packet rate is above @pkt_rate_high. + * @rx_max_coalesced_frames_high: Maximum number of packets to be received + * before an RX interrupt, when the packet rate is above @pkt_rate_high. * @tx_coalesce_usecs_high: How many usecs to delay a TX interrupt after * a packet is sent, when the packet rate is above @pkt_rate_high. - * @tx_max_coalesced_frames_high: How many packets to delay a TX interrupt - * after a packet is sent, when the packet rate is above @pkt_rate_high. + * @tx_max_coalesced_frames_high: Maximum number of packets to be sent before + * a TX interrupt, when the packet rate is above @pkt_rate_high. * @rate_sample_interval: How often to do adaptive coalescing packet rate * sampling, measured in seconds. Must not be zero. * -- 1.7.4.4 -- Ben Hutchings, Staff Engineer, Solarflare Not speaking for my employer; that's the marketing department's job. They asked us to note that Solarflare product names are trademarked.