From: David Mosberger <davidm@napali.hpl.hp.com>
To: "David S. Miller" <davem@redhat.com>
Cc: davidm@hpl.hp.com, davidm@napali.hpl.hp.com,
scott.feldman@intel.com, linux-kernel@vger.kernel.org,
netdev@oss.sgi.com
Subject: Re: [patch] e1000 TSO parameter
Date: Tue, 15 Jul 2003 23:32:48 -0700 [thread overview]
Message-ID: <16148.61840.663255.863176@napali.hpl.hp.com> (raw)
In-Reply-To: <20030715183911.1c18cc15.davem@redhat.com>
>>>>> On Tue, 15 Jul 2003 18:39:11 -0700, "David S. Miller" <davem@redhat.com> said:
>> We could, but would it always be a win? Especially for
>> copy_from_user(). Most of the time, that data remains cached, so
>> I don't think we'd want to use non-temporal stores on those (in
>> general). csum_and_copy_from_user() isn't well optimized yet.
>> Let's see if I can find a volunteer... ;-)
DaveM> No, I mean "bypass L2 cache on miss" for stores. Don't tell
DaveM> me IA64 doesn't have that? 8) I certainly didn't mean "always
DaveM> bypass L2 cache" for stores :-)
What I'm saying is that I almost always want copy_user() to put the
destination data in the cache, even if it isn't cached yet. Many
copy_user() calls are for for data structures that easily fit in the
cache and the data is usually used quickly afterwards.
As for cache-hints supported by IA64: the architecture supports
various non-temporal hints (non-temporal in 1st, 2nd, or all
cache-levels). How these hints are implemented depends on the chip.
On McKinley, non-temporal hints are generally implemented by storing
the data in the cache without updating the LRU info. So if the data
is already there, it will stay cached (until a victim is needed).
--david
next prev parent reply other threads:[~2003-07-16 6:18 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-07-15 4:42 [patch] e1000 TSO parameter Feldman, Scott
2003-07-15 4:45 ` David S. Miller
2003-07-15 4:57 ` David Mosberger
2003-07-15 5:31 ` David Mosberger
2003-07-15 5:38 ` David S. Miller
2003-07-15 23:01 ` David Mosberger
2003-07-16 1:39 ` David S. Miller
2003-07-16 6:32 ` David Mosberger [this message]
2003-07-16 6:30 ` David S. Miller
2003-07-29 6:53 ` Anton Blanchard
2003-07-15 5:11 Feldman, Scott
2003-07-16 0:27 Feldman, Scott
2003-07-16 0:41 ` David Mosberger
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