On Sun, 28 Jul 2013, dormando wrote:
> > Yes. > > OS doesn't pre-allocate the full buffer. > > > > Yes. > > Memcached should easily handle million concurrent idle connections (given > > enough memory). > > > > Except, if user has only allocated 512MB/1GB RAM for TCP, it is "possible" > > at runtime only four connections have eaten up all the memory, which > > could lead to connection refused or some other errors. > > > > Lets revisit the question. > > Is memcached unable to handle large no of concurrent connection? > > Usually no. Under some circumstances. Yes. > > > > And yes, don't guess. Just try it. Open <server_tcp_mem/256MB> connections > > with large multi-get request (response > 256MB) and don't read them at > > client side. And then try opening more connections. > > Usually no?? Are you sure you mean usually it can't handle it? That is > insanely wrong. "is memcached unable to handle" -> "usually no" -> so many negatives. "memcached is usually able to handle a large number of connections" -> true. The rest of my e-mail is correct though. Unless you're on some weird OS it's not going to use 256 megs of buffer, and unless you're on a very slow link and not/ever reading the data it's not going to be an issue. > Memcached runs on LAN's almost all of the time. There are almost NO > buffers stuck in use because of the low latency. This isn't an internet > facing tool, wherein you have to tune that more carefully and leave a lot > more free memory for TCP retransmits. Connections to memcached use a > handful of kilobytes. > > So very few people are going to run into this problem, complaining about > it is nothing short of alarmist. > > It's also never going to be 256MB: The actual memory used is limited (in > linux) by the tcp_rmem and tcp_wmem set of sysctl's. Even when people > aggressively tune those, they set the maximums around 16 megabytes. > Usually it's much lower than that. SENDBUF can't use more than what's in > wmem. > > -- > > --- > You received this message because you are subscribed to the Google Groups > "memcached" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > For more options, visit https://groups.google.com/groups/opt_out. > > > -- --- You received this message because you are subscribed to the Google Groups "memcached" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/groups/opt_out.
