Messages in this thread | | | Date | Mon, 25 Jun 2012 07:36:47 -0500 | From | Cliff Wickman <> | Subject | Re: [PATCH 3/3] x86: UV2 BAU hang workarounds |
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On Mon, Jun 25, 2012 at 12:03:21PM +0200, Ingo Molnar wrote: > > * Cliff Wickman <cpw@sgi.com> wrote: > > > On SGI's UV2 the BAU (Broadcast Assist Unit) driver can hang under a > > heavy load. To cure this: > > > > - Disable the UV2 extended status mode (see UV2_EXT_SHFT), as this > > mode changes BAU behavior in more ways then just delivering an extra bit > > of status. Revert status to just two meaningful bits, like UV1. > > - Use no IPI-style resets on UV2. Just give up the request for whatever the > > reason it failed and let it be accomplished with the legacy IPI method. > > - Use no alternate sending descriptor (the former UV2 workaround > > bcp->using_desc and handle_uv2_busy() stuff). Just disable the use of the > > BAU for a period of time in favor of the legacy IPI method when the h/w bug > > leaves a descriptor busy. > > -- new tunable: giveup_limit determines the threshold at which a hub is > > so plugged that it should do all requests with the legacy IPI method for a > > period of time > > -- generalize disable_for_congestion() (renamed disable_for_period()) for > > use whenever a hub should avoid using the BAU for a period of time > > > > Misc: > > - fix find_another_by_swack(), which is part of the UV2 bug workaround > > - correct and clarify the statistics (new stats s_overipilimit s_giveuplimit > > s_enters s_ipifordisabled s_plugged s_congested) > > Sigh, it looks like something that ought to be 7 successive, > easy to review commits got mixed up into a single, huge, hard to > review commit. How did that happen? > > Thanks, > > Ingo
Hi Ingo,
Yes, admittedly large. This patch was the 'bottom line' of a great deal of experimentation on how to work around some hardware problems with the bau. This is what remains after pulling out the unnecessary or unhelpful attempts. I could break it up for review purposes, if you think anyone would want to examine each component. You sound like you're willing to spend that time and effort. Yes?
-Cliff
-- Cliff Wickman SGI cpw@sgi.com (651) 683-3824
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