From: Russ Cox <rsc@swtch.com>
To: Fans of the OS Plan 9 from Bell Labs <9fans@9fans.net>
Subject: Re: [9fans] etherigbe.c using _xinc?
Date: Tue, 8 Dec 2009 11:35:26 -0800 [thread overview]
Message-ID: <dd6fe68a0912081135g5f051f33u25af76c81e87dc66@mail.gmail.com> (raw)
In-Reply-To: <5d1347dfd611729cd82ac5bc0ca79c92@coraid.com>
> because it's not a Ref. unfortunately, if it were
> a Ref, it would be much faster. _xinc is deadly
> slow even if there is no contention on x86.
do you have numbers to back up this claim?
you are claiming that the locked XCHGL
in tas (pc/l.s) called from lock (port/taslock.c)
called from incref (port/chan.c) is "much faster"
than the locked INCL in _xinc (pc/l.s).
it seems to me that a locked memory bus
is a locked memory bus.
also, when up != nil (a common condition),
lock does a locked INCL and DECL
(_xinc and _xdec) in addition to the tas,
which seems like strictly more work than
a single _xinc.
russ
next prev parent reply other threads:[~2009-12-08 19:35 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-12-08 16:25 Venkatesh Srinivas
2009-12-08 16:36 ` erik quanstrom
2009-12-08 19:35 ` Russ Cox [this message]
2009-12-08 19:52 ` John Floren
2009-12-08 20:00 ` erik quanstrom
2009-12-08 23:52 ` Russ Cox
[not found] <<dd6fe68a0912081552s30851f04n109e56479bb423cb@mail.gmail.com>
2009-12-09 0:32 ` erik quanstrom
2009-12-09 1:05 ` Russ Cox
[not found] <<dd6fe68a0912081705q6fad8a6cl20ca648397070dae@mail.gmail.com>
2009-12-09 2:04 ` erik quanstrom
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