Date: Tue, 5 Feb 2013 14:11:52 -0500 From: John Baldwin <jhb@freebsd.org> To: Randall Stewart <rrs@lakerest.net> Cc: freebsd-net@freebsd.org, Robert Watson <rwatson@freebsd.org>, Jack Vogel <jfvogel@gmail.com>, Kip Macy <kmacy@freebsd.org> Subject: Re: Driver patch to look at... Message-ID: <201302051411.52495.jhb@freebsd.org> In-Reply-To: <00075DDD-73A1-4CA4-9574-036D43B071D9@lakerest.net> References: <D3AA078A-CD19-4228-A019-BE9C985895E2@lakerest.net> <990BD290-643B-4BC7-8D64-6D4CE987025A@lakerest.net> <00075DDD-73A1-4CA4-9574-036D43B071D9@lakerest.net>
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On Tuesday, February 05, 2013 2:08:15 pm Randall Stewart wrote: > Hmm >=20 > wait, I could probably do the compare to whats in the ring buffer ;-D I wouldn't bother. The compare and branch is probably more expensive than the store. > R > On Feb 5, 2013, at 2:04 PM, Randall Stewart wrote: >=20 > > Hmm > >=20 > > That would trade off a stack pointer + a compare > > vs always doing the move. > >=20 > > Thats fine until I have to add the _mc() version, then the put > > back would be an atomic, and most of the time the return from > > this is probably not changed=85 > >=20 > > I really would prefer not to since the compare and maybe store vs > > the always store.. though the same now, would be far more expensive > > in the _mc version.. if we do a _mc version of course ;-) > >=20 > > But I am willing to do whatever .. since this really needs to be fixed. > >=20 > > R > > On Feb 5, 2013, at 1:52 PM, John Baldwin wrote: > >=20 > >> On Tuesday, February 05, 2013 12:44:01 pm Randall Stewart wrote: > >>> Actually, no it is used. > >>>=20 > >>> If you look in if_var.h int he drbr_putback() function, it does > >>> a buf_ring_swap when the old mbuf pointer does not equal the > >>> new mbuf pointer. This *does* happen, I crashed at least once > >>> yesterday when the igb driver did something to free the original > >>> mbuf and return a new mbuf with the data (prepend or some such). > >>>=20 > >>> I also have found several issues that I have fixed this morning.. its= been > >>> crash city on my test beds.. > >>>=20 > >>> Here is the latest patch with all fixes and suggested changes from em= aste=20 > >> (thanks Ed) > >>=20 > >> Actually, one more suggestion then (since you have to keep putback). = It > >> would be nice to not have to require 'snext' in all the callers. How > >> about replace buf_ring_swap() with a buf_ring_putback_sc() that accept= s the > >> mbuf and just stores it at the head unconditionally and have drbr_putb= ack() > >> use that? > >>=20 > >> --=20 > >> John Baldwin > >> _______________________________________________ > >> freebsd-net@freebsd.org mailing list > >> http://lists.freebsd.org/mailman/listinfo/freebsd-net > >> To unsubscribe, send any mail to "freebsd-net-unsubscribe@freebsd.org" > >>=20 > >=20 > > ------------------------------ > > Randall Stewart > > 803-317-4952 (cell) > >=20 > > _______________________________________________ > > freebsd-net@freebsd.org mailing list > > http://lists.freebsd.org/mailman/listinfo/freebsd-net > > To unsubscribe, send any mail to "freebsd-net-unsubscribe@freebsd.org" > >=20 >=20 > ------------------------------ > Randall Stewart > 803-317-4952 (cell) >=20 >=20 =2D-=20 John Baldwin
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