Messages in this thread | | | Date | Thu, 03 Dec 2009 18:04:14 +0100 | From | Eric Dumazet <> | Subject | Re: seeing strange values for tcp sk_rmem_alloc |
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Chris Friesen a écrit : > On 12/01/2009 11:52 AM, Eric Dumazet wrote: > >> But be careful of sender tcp stack : It might be delayed a bit, >> because it waits for receiver to open its window (slow start) >> >> You probably need something like >> >> while (1) { >> send(fd1, buffer, 2Kbytes); >> sleep(2); // let tcp stack flush its write buffers >> display_sk_rmem_alloc(fd2); >> } > > Ah, that makes a difference. But the results (see below) still look > odd. For this test, /proc/sys/net/core/rmem_default is 118784. For > some reason sk_rmem_alloc gets bumped by 16KB when I only send 2KB of > data, and it drops back down again every 6 packets. > > Chris
Might be because you use loopback device ? ;)
ifconfig lo | grep MTU UP LOOPBACK RUNNING MTU:16436 Metric:1
After a while (when hitting rcvbuf limit), tcp stack performs skb collapses, to reduce ram usage.
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