David Schwartz

16,550 reputation

11438

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	location	Murphys, CA
	age	43
visits	member for	1 year, 9 months
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I am OpenCoin's Chief Cryptographer and one of the architects of the Ripple payment system.

I live in California's Gold Country, east of Sacramento.

Bitcoin: 1Gonhezk1ScHaFqUSYH9VQThaDS4PJSq1o

	16,550 reputation	bio	website		visits	member for	1 year, 9 months
11438 badges		location	Murphys, CA		seen	17 mins ago

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Apr 5	comment	When the JVM is doing a complete GC, is it expected to see a large number of page fault/sec? That is also called a soft page fault. A "page fault" is a fault triggered by accessing a page. A "hard page fault" (or "major page fault") is a page fault that requires slow I/O (disk, network, etcetera). A "soft page fault" (or "minor page fault") is a page fault that does not.
Apr 5	comment	When the JVM is doing a complete GC, is it expected to see a large number of page fault/sec? What I'm talking about has little to do with whether a page is in the working set or not. It's about whether the process has recently accessed the page. In order to manage things like page eviction and working sets, the OS has to know which pages a process has recently accessed. To determine this, it periodically arranges it so that those accesses trigger a soft page fault. The fault handler marks the page accessed and changes it so that accesses won't trigger a soft page fault until later when it needs to know again. Removing pages from the working set is much later in the process.
Apr 5	comment	Is it possible to set up a management VLAN on HP switches without configuring routes on the WAN routers? You want three separate management VLANs? Do you want them to be able to communicate with each other? If so, something will have to route between the VLANs. (And likely, a VPN or tunnel will be needed between the locations to carry management traffic.)
Apr 5	comment	Can I ping my business's server from my home? Talk to the person who manages the network at your office. There's no way we could know how it's setup or whether that's supposed to work. Most likely, specific port forwarding would have to be configured, but we don't know.
Apr 4	comment	When the JVM is doing a complete GC, is it expected to see a large number of page fault/sec? There are soft page faults because without them, the operating system would have no way of knowing the memory was in use and thus no way to know it should keep the pages in memory. Operating systems use soft page faults to keep track of what memory is accessed. Since the pages haven't been accessed in a while, the operating system sets them to trigger a page fault when they're accessed so the OS will know they have been accessed. The first access to each such page (or collection of pages managed as a unit) triggers a page fault. A page fault means the OS did something when memory was accessed.
Apr 4	comment	MySQL VM running out of RAM @MichaelHampton: I agree. He has almost 5GB of cache. If his system was under memory pressure, it would have shrunk the cache.
Apr 4	comment	KVM and RAM Cache No. It's because it has nothing better to do with the RAM. What else could it do?
Apr 4	comment	KVM and RAM Cache What better use does it have for the RAM? What else could it do?
Apr 4	comment	KVM and RAM Cache It's really not clear what you're asking. Do you have some kind of problem you want help with? Or are you just curious what `cache=write-through` does? Or what? Your system has no better use for its RAM than cache. The cache is reducing the number of disk reads and writes and thereby improving performance. Your system has swapped a microscopic amount of data that hasn't been accessed in a very long time. This allows the system to discard that information without having to swap it out in the future, should it encounter high memory demand.
Apr 4	comment	KVM and RAM Cache Anything to do with what? We don't know what your issue is. You haven't told us. If you are experiencing a problem or something abnormal, you haven't said so.
Apr 4	comment	MySQL VM running out of RAM Can you paste the output of `top` while the system is running out of RAM? Seeing the output during normal operation, with 6.5GB used as cache, doesn't help us much.
Apr 4	comment	KVM and RAM Cache You forgot to ask a question. Everything you describe is perfectly normal. Do you have an actual issue?
Apr 4	comment	Unexplained DNS Routing Issue How can it be both that some users find the domain doesn't resolve and global DNS checks are okay? What does "intermittent connectivity" mean?
Apr 4	comment	Solaris memory allocation How long is the `brk` operation taking? More than a second? Can you paste the `truss` output around the `brk` operation?
Apr 4	comment	No link on em1, but that port shares an interface with IPMI, which has network connectivity Did you `ifconfig` the interface `up`?
Apr 4	comment	npm install, but can't run A symlink is created to the javascript library so that other javascript programs can use it. That has nothing to do with what happens to binaries.
Apr 3	comment	Two Bonded Gigabyte NICs are limited to 100Mb How exactly are these devices interconnected?
Apr 3	comment	Why sendmail is accepting mails for hostname not present in local-host-names file? What do you mean by "is accepting"? Do you mean it's delivering the mails locally?
Apr 3	comment	How do you do IP Nullrouting It depends what the attack is hurting (Just the customer? An entire datacenter? A nationwide backbone?) and what the provider's network architecture looks like. Sometimes, the null route is propagated all the way back to the backbone's interconnects with other backbones. In the simple case where one customer's inbound bandwidth is the only issue, it can be just null routed in the router that services that customer's connection.
Apr 2	comment	How do you do IP Nullrouting DDoS defense is just not that simple. You have to understand the specific threat, figure out how it's hurting you, and form a specific response aimed at the particular mechanism. There's no one right place to put the one magic bullet.