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Date:      Sat, 01 Dec 2001 08:55:42 +1030
From:      Richard Sharpe <sharpe@ns.aus.com>
To:        Alfred Perlstein <bright@mu.org>
Cc:        rsharpe@ns.aus.com, Matthew Dillon <dillon@apollo.backplane.com>, Alexander Haderer <alexander.haderer@charite.de>, freebsd-hackers@FreeBSD.ORG
Subject:   Re: FreeBSD performing worse than Linux?
Message-ID:  <3C080766.5030600@ns.aus.com>
References:  <20011128153817.T61580@monorchid.lemis.com> <15364.38174.938500.946169@caddis.yogotech.com> <20011128104629.A43642@walton.maths.tcd.ie> <5.1.0.14.1.20011130181236.00a80160@postamt1.charite.de> <200111302047.fAUKlT811090@apollo.backplane.com> <3C07FCFF.4070008@ns.aus.com> <20011130150843.L46769@elvis.mu.org>

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Alfred Perlstein wrote:

> * Richard Sharpe <sharpe@ns.aus.com> [011130 15:02] wrote:
>>The traffic in the tbench case is SMB taffic. Request/response, with a

>>mixture of small requests and responses, and big request/small response 

>>or small request/big response, where big is 64K.
>>
>>
>>I have switched off newreno, and it made no difference. I have switched 
>>off delayed_ack, and it reduced performance about 5 percent. I have made 
>>sure that SO_SNDBUF and SO_RCVBUF were set to 131072 (which seems to be 
>>the max), and it increased performance marginally (like about 2%), but 
>>consistently.
>>
>>I am still analysing the packet traces I have, but it seems to me that 
>>the crucial difference is Linux seems to delay longer before sending 
>>ACKs, and thus sends less ACKs. Since the ACK is piggybacked in the 
>>response (or the next request), it all works fine, and the 
>>reponse/request gets there sooner.
>>
>>However, I have not convinced myself that the saving of 20uS or so per 
>>request/response pair accounts for some 40+ Mb/s.
>>

> Can you try these two commands:
> 
> sysctl -w net.inet.tcp.recvspace=65536
> sysctl -w net.inet.tcp.sendspace=65536


Yes, that is what I did ... 


-- 
Richard Sharpe, rsharpe@ns.aus.com, LPIC-1
www.samba.org, www.ethereal.com, SAMS Teach Yourself Samba
in 24 Hours, Special Edition, Using Samba


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