Date: Mon, 07 Jan 2013 10:47:29 -0800 From: Oleksandr Tymoshenko <gonzo@bluezbox.com> To: Alan Cox <alc@rice.edu> Cc: svn-src-head@freebsd.org, svn-src-all@freebsd.org, src-committers@freebsd.org, Andre Oppermann <andre@freebsd.org> Subject: Re: svn commit: r243631 - in head/sys: kern sys Message-ID: <50EB1841.5030006@bluezbox.com> In-Reply-To: <50DD081E.8000409@bluezbox.com> References: <201211272119.qARLJxXV061083@svn.freebsd.org> <ABB3E29B-91F3-4C25-8FAB-869BBD7459E1@bluezbox.com> <50C1BC90.90106@freebsd.org> <50C25A27.4060007@bluezbox.com> <50C26331.6030504@freebsd.org> <50C26AE9.4020600@bluezbox.com> <50C3A3D3.9000804@freebsd.org> <50C3AF72.4010902@rice.edu> <330405A1-312A-45A5-BB86-4969478D8BBD@bluezbox.com> <50D03E83.8060908@rice.edu> <50DD081E.8000409@bluezbox.com>
next in thread | previous in thread | raw e-mail | index | archive | help
On 12/27/2012 6:46 PM, Oleksandr Tymoshenko wrote: > On 12/18/2012 1:59 AM, Alan Cox wrote: >> On 12/17/2012 23:40, Oleksandr Tymoshenko wrote: >>> On 2012-12-08, at 1:21 PM, Alan Cox <alc@rice.edu> wrote: >>> >>>> On 12/08/2012 14:32, Andre Oppermann wrote: >>> .. skipped .. >>> >>>>> The trouble seems to come from NSFBUFS which is (512 + maxusers * 16) >>>>> resulting in a kernel map of (512 + 400 * 16) * PAGE_SIZE = 27MB. >>>>> This >>>>> seem to be pushing it with the smaller ARM kmap layout. >>>>> >>>>> Does it boot and run when you set the tunable kern.ipc.nsfbufs=3500? >>>>> >>>>> ARM does have a direct map mode as well which doesn't require the >>>>> allocation >>>>> of sfbufs. I'm not sure which other problems that approach has. >>>>> >>>> Only a few (3?) platforms use it. It reduces the size of the user >>>> address space, and translation between physical addresses and >>>> direct map >>>> addresses is not computationally trivial as it is on other >>>> architectures, e.g., amd64, ia64. However, it does try to use large >>>> page mappings. >>>> >>>> >>>>> Hopefully alc@ (added to cc) can answer that and also why the kmap of >>>>> 27MB >>>>> manages to wrench the ARM kernel. >>>>> >>>> Arm does not define caps on either the buffer map size (param.h) or >>>> the >>>> kmem map size (vmparam.h). It would probably make sense to copy these >>>> definitions from i386. >>> Adding caps didn't help. I did some digging and found out that >>> although address range >>> 0xc0000000 .. 0xffffffff is indeed valid for ARM in general actual >>> KVA space varies for >>> each specific hardware platform. This "real" KVA is defined by >>> <virtual_avail, virtual_end> >>> pair and ifI use them instead of <VM_MIN_KERNEL_ADDRESS, >>> VM_MAX_KERNEL_ADDRESS> >>> in init_param2 function my pandaboard successfully boots. Since >>> former pair is used for defining >>> kernel_map boundaries I believe it should be used for auto tuning as >>> well. >> >> That makes sense. However, "virtual_avail" isn't the start of the >> kernel address space. The kernel map always starts at >> VM_MIN_KERNEL_ADDRESS. (See kmem_init().) "virtual_avail" represents >> the next unallocated virtual address in the kernel address space at an >> early point in initialization. "virtual_avail" and "virtual_end" aren't >> used after that, or outside the VM system. Please use >> vm_map_min(kernel_map) and vm_map_max(kernel_map) instead. > > I checked: kernel_map is not available (NULL) at this point. So we > can't use it to > determine real KVA size. Closest thing we can get is > virtual_avail/virtual_end pair. > > Andre, could you approve attached patch for commit or suggest better > solution? Any update on this one? Can I proceed with commit?
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?50EB1841.5030006>