[rds-devel] RDS IB transport software flow control?

Olaf Kirch olaf.kirch at oracle.com
Wed Nov 7 05:17:17 PST 2007


On Wednesday 07 November 2007 13:18, Richard Frank wrote:
> Who sets - max recv memory ?

It's a sysctl, and it defaults to one third of all available RAM,
which is pretty generous IMO :)

> Part of the reasoning for so_rcvbuf - is that this is an existing 
> application tuning knob - which for example, one app I'm familiar with 
> uses today.

Yes, and it can continue to do so.

> Senders can only send so_sndbuf - worth of sends - without getting back 
> "credits" via the RC ACK. So the recving side has the opportunity to 
> send back the congestion message (NAK) along with / or before the ACK.
> 
> This somewhat bounds the recv memory to sender so_sndbuf * number of 
> senders to a destination - which is probably not that limiting...

That was my point, indeed.

Olaf
-- 
Olaf Kirch  |  --- o --- Nous sommes du soleil we love when we play
okir at lst.de |    / | \   sol.dhoop.naytheet.ah kin.ir.samse.qurax



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