Date: Wed, 30 Nov 2011 17:53:04 +0100 From: Andreas Tobler <andreast-list@fgznet.ch> To: Kostik Belousov <kostikbel@gmail.com> Cc: FreeBSD Arch <freebsd-arch@freebsd.org> Subject: Re: powerpc64 malloc limit? Message-ID: <4ED65F70.7050700@fgznet.ch> In-Reply-To: <20111130162236.GA50300@deviant.kiev.zoral.com.ua> References: <4ED5BE19.70805@fgznet.ch> <20111130162236.GA50300@deviant.kiev.zoral.com.ua>
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On 30.11.11 17:22, Kostik Belousov wrote: > On Wed, Nov 30, 2011 at 06:24:41AM +0100, Andreas Tobler wrote: >> All, >> >> while working on gcc I found a very strange situation which renders my >> powerpc64 machine unusable. >> The test case below tries to allocate that much memory as 'wanted'. The >> same test case on amd64 returns w/o trying to allocate mem because the >> size is far to big. >> >> I couldn't find the reason so far, that's why I'm here. >> >> As Nathan pointed out the VM_MAXUSER_SIZE is the biggest on powerpc64: >> #define VM_MAXUSER_ADDRESS (0x7ffffffffffff000UL) >> >> So, I'd expect a system to return an allocation error when a user tries >> to allocate too much memory and not really trying it and going to be >> unusable. Iow, I'd exepect the situation on powerpc64 as I see on amd64. >> >> Can anybody explain me the situation, why do I not have a working limit >> on powerpc64? >> >> The machine itself has 7GB RAM and 12GB swap. The amd64 where I compared >> has around 4GB/4GB RAM/swap. >> >> TIA, >> Andreas >> >> include<stdlib.h> >> #include<stdio.h> >> >> int main() >> { >> void *p; >> >> p = (void*) malloc (1152921504606846968ULL); >> if (p != NULL) >> printf("p = %p\n", p); >> >> printf("p = %p\n", p); >> return (0); >> } > > First, you should provide details of what consistutes 'the unusable > machine situation' on powerpc. I can not login anymore, everything is stuck except the core control mechanisms for example the fan controller. Top reports 'ugly' figures, below from a earlier try: last pid: 6790; load averages: 0.78, 0.84, 0.86 up 0+00:34:52 22:42:29 47 processes: 1 running, 46 sleeping CPU: 0.0% user, 0.0% nice, 15.4% system, 11.8% interrupt, 72.8% idle Mem: 5912M Active, 570M Inact, 280M Wired, 26M Cache, 104M Buf, 352K Free Swap: 12G Total, 9904M Used, 2383M Free, 80% Inuse, 178M Out PID USERNAME THR PRI NICE SIZE RES STATE C TIME WCPU COMMAND 6768 andreast 1 52 01073741824G 6479M pfault 1 0:58 18.90% 31370. And after my mem and swap are full I see swap_pager_getswapspace(16) failed. In this state I can only power-cycle the machine. > That said, on amd64 the user map is between 0 and 0x7fffffffffff, which > obviously less then the requested allocation size 0x100000000000000. > If you look at the kdump output on amd64, you will see that malloc() > tries to mmap() the area, fails and retries with obreak(). Default > virtual memory limit is unlimited, so my best quess is that on amd64 > vm_map_findspace() returns immediately. > > On powerpc64, I see no reason why vm_map_entry cannot be allocated, but > please note that vm object and pages shall be only allocated on demand. > So I am curious how does your machine breaks and where. I would expect that the 'system' does not allow me to allocate that much of ram. Thanks! Andreas
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