Date: Fri, 11 Jan 2013 17:08:24 +0530 From: "Jayachandran C." <jchandra@freebsd.org> To: Andre Oppermann <andre@freebsd.org> Cc: svn-src-head@freebsd.org, svn-src-all@freebsd.org, src-committers@freebsd.org, Oleksandr Tymoshenko <gonzo@bluezbox.com>, Alan Cox <alc@rice.edu> Subject: Re: svn commit: r243631 - in head/sys: kern sys Message-ID: <CA%2B7sy7CkdoyScOEDEXWuwJxjCS5zTcC8_fu9isCeTFxT8opNJQ@mail.gmail.com> In-Reply-To: <50EB415F.8020405@freebsd.org> 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> <50EB1841.5030006@bluezbox.com> <50EB22D2.6090103@rice.edu> <50EB415F.8020405@freebsd.org>
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On Tue, Jan 8, 2013 at 3:12 AM, Andre Oppermann <andre@freebsd.org> wrote: > On 07.01.2013 20:32, Alan Cox wrote: >> >> On 01/07/2013 12:47, Oleksandr Tymoshenko wrote: >>> >>> 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? >>> >> >> Sorry, I've been away from my e-mail since the 30th, and I'm now in the >> process of getting caught up. Give me a day or so to look at this. I see an issue with commit on MIPS XLP platform as well. With 16 GB physical memory, the ncallout is calculated to be 538881 (since it is based on maxfiles - which is now based on the physical memory). Due to this, the callwheel allocation per cpu is 16MB (callwheelsize is 1MB). And on a 32 CPU machine, the total allocation for callouts comes to 32*16MB = 512MB. I have worked around this issue for now by increasing VM_KMEM_SIZE_MAX (which is 200MB now) - but I think a better fix is needed for this. JC.
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