From: Mitchell Blank Jr <mitch@sfgoth.com>
To: Stephen Hemminger <shemminger@osdl.org>
Cc: Steve Modica <modica@sgi.com>, netdev@oss.sgi.com
Subject: Re: do_gettimeofday
Date: Thu, 2 Oct 2003 13:46:36 -0700 [thread overview]
Message-ID: <20031002204636.GB30579@gaz.sfgoth.com> (raw)
In-Reply-To: <20031002125625.72b8c0a7.shemminger@osdl.org>
Stephen Hemminger wrote:
> Two problems:
> a. xtime is limited to HZ resolution which is insufficient for more advanced
> packet schedulers and rtt estimation.
> b. unlocked access to xtime is unsafe because it is not atomic!
>
> ATM is busted if it does this.
It got fixed in 2.5 (when skb->stamp got changed to nanosecond resolution
so it broke the compile to do it the old way) You can use LXR to see all
of the xtime users as of 2.6.0-test2:
http://lxr.linux.no/ident?v=2.6.0-test2&i=xtime
The reason that ATM _had_ been using xtime was not for performance. When
the ATM code was originally written (during the 1.X kernels) all network
drivers used xtime directly. At some point the network drivers were
mass-updated to use do_gettimeofday() but ATM had not been merged into
the main tree yet so it missed the conversion.
-Mitch
next prev parent reply other threads:[~2003-10-02 20:46 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-10-02 18:32 do_gettimeofday Steve Modica
2003-10-02 19:29 ` do_gettimeofday Andi Kleen
2003-10-02 19:56 ` do_gettimeofday Stephen Hemminger
2003-10-02 20:46 ` Mitchell Blank Jr [this message]
2003-10-03 7:41 ` do_gettimeofday David S. Miller
2003-10-03 8:26 ` do_gettimeofday Mitchell Blank Jr
2003-10-03 8:27 ` do_gettimeofday David S. Miller
2003-10-03 8:48 ` do_gettimeofday Mitchell Blank Jr
2003-10-03 8:52 ` do_gettimeofday David S. Miller
2003-10-03 9:26 ` do_gettimeofday Mitchell Blank Jr
2003-10-03 9:23 ` do_gettimeofday David S. Miller
2003-10-03 16:42 ` do_gettimeofday Ben Greear
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