Messages in this thread | | | Date | Mon, 25 Jun 2012 12:03:21 +0200 | From | Ingo Molnar <> | Subject | Re: [PATCH 3/3] x86: UV2 BAU hang workarounds |
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* 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
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