Date: Mon, 24 Sep 2007 09:28:36 -0600 From: Scott Long <scottl@samsco.org> To: Ruslan Ermilov <ru@freebsd.org> Cc: Darren Reed <darrenr@freebsd.org>, freebsd-current@freebsd.org, Larry Rosenman <ler@lerctr.org> Subject: Re: panic: kmem_malloc(131072): kmem_map too small (AMD64) Message-ID: <46F7D7A4.5090007@samsco.org> In-Reply-To: <20070924144210.GA82735@team.vega.ru> References: <20070921102946.T11189@borg> <46F415BF.9010500@FreeBSD.org> <20070921140550.D96923@thebighonker.lerctr.org> <46F41CFF.6080108@FreeBSD.org> <46F58799.1030702@freebsd.org> <46F58B21.8030307@FreeBSD.org> <20070924091558.GB32006@team.vega.ru> <46F78C59.1020801@FreeBSD.org> <20070924080347.O84223@thebighonker.lerctr.org> <20070924144210.GA82735@team.vega.ru>
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Ruslan Ermilov wrote: > On Mon, Sep 24, 2007 at 08:04:33AM -0500, Larry Rosenman wrote: >> On Mon, 24 Sep 2007, Kris Kennaway wrote: >> >>> Ruslan Ermilov wrote: >>>> On Sat, Sep 22, 2007 at 11:37:37PM +0200, Kris Kennaway wrote: >>>>> Darren Reed wrote: > [...] >>>>>> Stupid question, perhaps, but is vm.kmem_size/vm.kmem_size_max limited >>>>>> by physical RAM? >>>>> Yes. >>>> To be precise, it's actually limited by 2 * sizeof(physical RAM). >>>> It's still size of a _virtual_ memory map (kmem_map), after all: >>>> : /* >>>> : * Limit kmem virtual size to twice the physical memory. >>>> : * This allows for kmem map sparseness, but limits the size >>>> : * to something sane. Be careful to not overflow the 32bit >>>> : * ints while doing the check. >>>> : */ >>>> : if (((vm_kmem_size / 2) / PAGE_SIZE) > cnt.v_page_count) >>>> : vm_kmem_size = 2 * cnt.v_page_count * PAGE_SIZE; >>> Well OK, but that seems pretty dangerous, because it leaves open a pathway >>> to exhaust all of physical memory and presumably panic. >> is KVA pageable? Is the kmem_map dedicating non-pageable memory? >> > kmem_map is used to map memory for the zone allocator, including > malloc(9). > >> I've set my vm.kmem_max to 1G, (on a 4G amd64 box). Is that reasonable? >> > It just means that your kernel can "malloc" up to 1G of memory. > You're all missing the point, I hate to say. What happened is that a change was made recently to more accurately account for allocated memory. Now people are getting kmem_map_too_small panics that weren't getting them before. So while the accounting is now more accurate, the outcome is actually harmful. That needs to be fixed before the release. Scotthome | help
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