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Message-Id: <20130905.142530.732425484460470485.davem@davemloft.net>
Date: Thu, 05 Sep 2013 14:25:30 -0400 (EDT)
From: David Miller <davem@...emloft.net>
To: Vineet.Gupta1@...opsys.com
Cc: netdev@...r.kernel.org, Alexey.Brodkin@...opsys.com,
linux-kernel@...r.kernel.org, arc-linux-dev@...opsys.com
Subject: Re: [PATCH] ethernet/arc/arc_emac: Fix huge delays in large file
copies
From: Vineet Gupta <Vineet.Gupta1@...opsys.com>
Date: Wed, 4 Sep 2013 17:17:15 +0530
> copying large files to a NFS mounted host was taking absurdly large
> time.
>
> Turns out that TX BD reclaim had a sublte bug.
>
> Loop starts off from @txbd_dirty cursor and stops when it hits a BD
> still in use by controller. However when it stops it needs to keep the
> cursor at that very BD to resume scanning in next iteration. However it
> was erroneously incrementing the cursor, causing the next scan(s) to
> fail too, unless the BD chain was completely drained out.
>
> [ARCLinux]$ ls -l -sh /disk/log.txt
> 17976 -rw-r--r-- 1 root root 17.5M Sep /disk/log.txt
>
> ========== Before =====================
> [ARCLinux]$ time cp /disk/log.txt /mnt/.
> real 31m 7.95s
> user 0m 0.00s
> sys 0m 0.10s
>
> ========== After =====================
> [ARCLinux]$ time cp /disk/log.txt /mnt/.
> real 0m 24.33s
> user 0m 0.00s
> sys 0m 0.19s
>
> Signed-off-by: Vineet Gupta <vgupta@...opsys.com>
Applied.
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