Date: Sun, 26 Jan 2014 11:54:05 -0700 From: Warner Losh <imp@bsdimp.com> To: Juli Mallett <jmallett@FreeBSD.org> Cc: "freebsd-mips@FreeBSD.org" <freebsd-mips@freebsd.org> Subject: Re: More trapframe panics Message-ID: <453F8F8F-41E5-4640-9683-5A8553AB0822@bsdimp.com> In-Reply-To: <CACVs6=-_N8aPEeFT5P8aTr1hkpmBWGwCt930wsGzg4YHxr8VKg@mail.gmail.com> References: <52E42A1B.3040907@rewt.org.uk> <CACVs6=--Qy_8poWdHdCXYKqkO22=dvHhW8=Uma8kLR%2BhCoZDxw@mail.gmail.com> <52E524BD.7090106@rlwinm.de> <CACVs6=-_N8aPEeFT5P8aTr1hkpmBWGwCt930wsGzg4YHxr8VKg@mail.gmail.com>
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On Jan 26, 2014, at 9:04 AM, Juli Mallett wrote: > On Sun, Jan 26, 2014 at 7:07 AM, Jan Bramkamp <crest@rlwinm.de> wrote: >> >> Would increasing KSTACK_PAGES from two to three or four help? What are >> the trade-offs involved in choosing KSTACK_PAGES for something like the >> EdgeMax Lite? > > > That's exactly what needs to happen in all 64-bit MIPS kernels. Unlike > some other architectures, KSTACK_PAGES cannot simply be increased, > however. All of the code which handles loading the kernel stack and > keeping it mapped, etc., assumes that it takes up exactly one TLB entry, > i.e. 2 pages. One could simply double KSTACK_PAGES for 64-bit builds and > modify the code to support the case of 2 or 4 pages, which would keep the > code as gross as it is today and not buy much flexibility, but might be > worthwhile as a short-term fix. Being able to support arbitrary values of > KSTACK_PAGES (or at least arbitrary multiples of 2 up to the maximum number > of wired TLB entries times 2) would be better. I hacked together a kludge that quadrupled this by going to the next larger page size for stack pages in the TLB, but hit something ugly when I did that... But I've lost that code, so maybe I should try again to see if I'm more clever the second time. This is one of the things that makes it hard to have a nice native build server on mips64... Warner
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