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Date: Tue, 08 Apr 2008 17:38:47 +0200 From: Juliusz Chroboczek <Juliusz.Chroboczek@....jussieu.fr> To: Andi Kleen <andi@...stfloor.org> Cc: netdev@...r.kernel.org Subject: Re: [PATCH] Stochastic Fair Blue queue discipline > (read Documentation/CodingStyle) Will do, thanks for the pointer. >> +static unsigned sfb_hash(struct sk_buff *skb, int hash, int filter, >> + struct sfb_sched_data *q) > I think we have multiple qdiscs now doing very similar such hashes. > Any chance this could be factored out into a common library function > first? I'll be glad to do so. Where shall I put it? > Getting high res time can be actually somewhat expensive on different > platforms. I would recommend to only use it if it's actually needed in > the inelastic flow case below and use jiffies to check for rehashing. Good point. > /dev/random is a precious resource (some systems have very little > true entropy) and getting that much data from it regularly is not > a good idea because you take it away from other users who really > need it In the default configuration, I'm getting 32 bytes every 10 minutes, which seemed reasonable. This code was copied from sch_sfq (function sfq_perturbation), which does the very same thing. > But in any case it is likely better you only get the > get_random_bytes() entropy once and then use that to init some kind > of RNG (either a secure one if it's for security or some random fast > one if it's not) and then use that output for rehashing. Could do, but in that case the RNG should be shared between sfq and sfb. Shall I simply use net_random (which calls random32) ? Juliusz -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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