From: Mitchell Blank Jr <mitch@sfgoth.com>
To: "David S. Miller" <davem@redhat.com>
Cc: netdev@oss.sgi.com
Subject: Re: do_gettimeofday
Date: Fri, 3 Oct 2003 01:48:47 -0700 [thread overview]
Message-ID: <20031003084847.GH42593@gaz.sfgoth.com> (raw)
In-Reply-To: <20031003012754.23de3f66.davem@redhat.com>
David S. Miller wrote:
> Doesn't work as-is. You'd have to not only store the timestamp and
> the cpu it was stored on, but also cross-call to that cpu to compute
> the correct timeval.
That's definately the worst case. You could have each CPU periodically
store its current {tsc,timeval} tuple in a per-cpu location and extrapolate
from that.
> That's really expensive and probably
> do_gettimeofday() is going to be faster in the long run compared to
> such a scheme.
It all depends on what percentage of skb's have ->stamp computed on a
CPU different from the one they came it on. For the common users of
->stamp won't they have stayed on the same CPU? The worst case of
doing a cross-cpu-call should only happen relatively rarely.
-Mitch
next prev parent reply other threads:[~2003-10-03 8:48 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 ` do_gettimeofday Mitchell Blank Jr
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 ` Mitchell Blank Jr [this message]
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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