From: Arnd Bergmann <arnd@arndb.de>
To: linuxppc-dev@ozlabs.org
Cc: akpm@osdl.org, James K Lewis <jklewis@us.ibm.com>,
linux-kernel@vger.kernel.org, netdev@vger.kernel.org,
Jeff Garzik <jgarzik@pobox.com>,
ens Osterkamp <Jens.Osterkamp@de.ibm.com>
Subject: Re: [PATCH 2/6]: powerpc/cell spidernet low watermark patch.
Date: Sat, 19 Aug 2006 01:09:13 +0200 [thread overview]
Message-ID: <200608190109.15129.arnd@arndb.de> (raw)
In-Reply-To: <20060818222146.GI26889@austin.ibm.com>
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WARNING: multiple messages have this Message-ID (diff)
From: Arnd Bergmann <arnd@arndb.de>
To: linuxppc-dev@ozlabs.org
Cc: akpm@osdl.org, James K Lewis <jklewis@us.ibm.com>,
linux-kernel@vger.kernel.org, netdev@vger.kernel.org,
Jeff Garzik <jgarzik@pobox.com>,
ens Osterkamp <Jens.Osterkamp@de.ibm.com>
Subject: Re: [PATCH 2/6]: powerpc/cell spidernet low watermark patch.
Date: Sat, 19 Aug 2006 01:09:13 +0200 [thread overview]
Message-ID: <200608190109.15129.arnd@arndb.de> (raw)
In-Reply-To: <20060818222146.GI26889@austin.ibm.com>
On Saturday 19 August 2006 00:21, Linas Vepstas wrote:
> + /* Measure the length of the queue. */
> + while (descr != card->tx_chain.head) {
> + status = descr->dmac_cmd_status & SPIDER_NET_DESCR_NOT_IN_USE;
> + if (status == SPIDER_NET_DESCR_NOT_IN_USE)
> + break;
> + descr = descr->next;
> + cnt++;
> + }
> + if (cnt == 0)
> + return;
> +
> + /* Set low-watermark 3/4th's of the way into the queue. */
> + descr = card->tx_chain.tail;
> + cnt = (cnt*3)/4;
> + for (i=0;i<cnt; i++)
> + descr = descr->next;
I wonder if calling this frequently results in a significant processing
overhead in the CPU. Does the spider_net_set_low_watermark function
show up in your profiles?
A more efficient implementation might be to mark one descriptor that
is at a fixed offset from the TX queue tail, so we only need to do
card->low_watermark->next->dmac_cmd_status |= SPIDER_NET_DESCR_TXDESFLG;
mb();
card->low_watermark->dmac_cmd_status &= ~SPIDER_NET_DESCR_TXDESFLG;
card->low_watermark = card->low_watermark->next;
when we queue another frame for TX.
Arnd <><
next prev parent reply other threads:[~2006-08-18 23:09 UTC|newest]
Thread overview: 55+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-08-18 22:07 [PATCH 0/6]: powerpc/cell spidernet ethernet driver update Linas Vepstas
2006-08-18 22:07 ` Linas Vepstas
2006-08-18 22:20 ` [PATCH 1/6]: powerpc/cell spidernet burst alignment patch Linas Vepstas
2006-08-18 22:51 ` Arnd Bergmann
2006-08-18 22:51 ` Arnd Bergmann
2006-08-18 22:21 ` [PATCH 2/6]: powerpc/cell spidernet low watermark patch Linas Vepstas
2006-08-18 23:09 ` Arnd Bergmann [this message]
2006-08-18 23:09 ` Arnd Bergmann
2006-08-20 6:31 ` Benjamin Herrenschmidt
2006-08-20 6:31 ` Benjamin Herrenschmidt
2006-08-20 10:03 ` Arnd Bergmann
2006-08-20 10:03 ` Arnd Bergmann
2006-08-23 21:36 ` Linas Vepstas
2006-08-23 21:36 ` Linas Vepstas
2006-08-23 22:03 ` David Miller
2006-08-23 22:03 ` David Miller
2006-08-18 22:23 ` [PATCH 3/6]: powerpc/cell spidernet stop error printing patch Linas Vepstas
2006-08-18 22:25 ` [PATCH 4/6]: powerpc/cell spidernet ethtool -i version number info Linas Vepstas
2006-08-18 22:56 ` Arnd Bergmann
2006-08-18 22:56 ` Arnd Bergmann
2006-08-18 22:26 ` [PATCH 5/6]: powerpc/cell spidernet bottom half Linas Vepstas
2006-08-18 23:03 ` Arnd Bergmann
2006-08-18 23:03 ` Arnd Bergmann
2006-08-19 0:56 ` [RFC] HOWTO use NAPI to reduce TX interrupts Arnd Bergmann
2006-08-19 0:56 ` Arnd Bergmann
2006-08-20 1:31 ` Stephen Hemminger
2006-08-20 1:31 ` Stephen Hemminger
2006-08-19 11:25 ` Arnd Bergmann
2006-08-19 11:25 ` Arnd Bergmann
2006-08-20 17:48 ` [RFC v2] " Arnd Bergmann
2006-08-20 17:48 ` Arnd Bergmann
2006-08-21 20:40 ` NAPI documentation Stephen Hemminger
2006-08-21 20:40 ` Stephen Hemminger
2006-08-21 22:05 ` David Miller
2006-08-21 22:05 ` David Miller
2006-08-21 22:09 ` Stephen Hemminger
2006-08-21 22:09 ` Stephen Hemminger
2006-08-21 22:17 ` David Miller
2006-08-21 22:17 ` David Miller
2006-08-21 23:52 ` [RFC] HOWTO use NAPI to reduce TX interrupts Linas Vepstas
2006-08-21 23:52 ` Linas Vepstas
2006-08-21 23:56 ` David Miller
2006-08-21 23:56 ` David Miller
2006-08-22 0:29 ` Roland Dreier
2006-08-22 0:29 ` Roland Dreier
2006-08-22 0:32 ` David Miller
2006-08-22 0:32 ` David Miller
2006-08-23 1:29 ` Shirley Ma
2006-08-23 1:29 ` Shirley Ma
2006-08-23 21:52 ` [PATCH 5/6]: powerpc/cell spidernet bottom half Linas Vepstas
2006-08-23 21:52 ` Linas Vepstas
2006-08-18 22:29 ` [PATCH 6/6]: powerpc/cell spidernet refine locking Linas Vepstas
-- strict thread matches above, loose matches on Subject: below --
2006-09-29 23:05 [PATCH 0/6]: powerpc/cell spidernet ethernet patches Linas Vepstas
2006-09-29 23:17 ` [PATCH 2/6]: powerpc/cell spidernet low watermark patch Linas Vepstas
2006-09-30 10:30 ` Arnd Bergmann
2006-09-30 10:30 ` Arnd Bergmann
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