Date: Mon, 2 Jul 2012 16:31:48 +0000 From: "Bjoern A. Zeeb" <bzeeb-lists@lists.zabbadoz.net> To: John Baldwin <jhb@freebsd.org> Cc: freebsd-current FreeBSD <freebsd-current@freebsd.org> Subject: Re: swp_pager_meta_build DoS printf Message-ID: <B60059D0-9ED8-430D-8D7D-275E4536AC94@lists.zabbadoz.net> In-Reply-To: <201207021036.45567.jhb@freebsd.org> References: <7BEE3948-EE35-48C2-B4B1-25E34087A4C4@lists.zabbadoz.net> <201207021036.45567.jhb@freebsd.org>
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On 2. Jul 2012, at 14:36 , John Baldwin wrote:
> On Sunday, July 01, 2012 8:23:31 am Bjoern A. Zeeb wrote:
>> Hey,
>>
>> hitting this printf in swp_pager_meta_build()
>>
>> if (uma_zone_exhausted(swap_zone)) {
>> printf("swap zone exhausted, increase kern.maxswzone\n");
>> vm_pageout_oom(VM_OOM_SWAPZ);
>> pause("swzonex", 10);
>> } else
>>
>> seems to be an effective way to put the machine into a state of no recovery
>> unless the memory situation would be able to clear itself. Not that it wouldn't
>> otherwise be any better but in addition having a couple of tenthousands of these
>> going to console as well is really not helpful to try to do anything either. Can
>> we make it a log() call or something?
>>
>> /bz
>>
>> PS: I am not sure as I have seen it on someone else's machines and it's
>> probably been ZFS that caused it. I unfortunately neither had a way to
>> get back in or break to a kernel debugger, so information is sparse.
>
> This used to be a silent deadlock before I added the printf() and the call to
> OOM. :-P Do you just want to ratelimit the printf? We have an API to ratelimit
> printf's already.
Ratelimit would be fine; I was writing that on the wrong time of the wrong day to
just get it out; could you do that?
/bz
--
Bjoern A. Zeeb You have to have visions!
It does not matter how good you are. It matters what good you do!
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