Date: Sat, 02 Feb 2019 23:42:25 +0000 From: bugzilla-noreply@freebsd.org To: net@FreeBSD.org Subject: [Bug 235031] [em] em0: poor NFS performance, strange behavior Message-ID: <bug-235031-7501-ove912fY3g@https.bugs.freebsd.org/bugzilla/> In-Reply-To: <bug-235031-7501@https.bugs.freebsd.org/bugzilla/> References: <bug-235031-7501@https.bugs.freebsd.org/bugzilla/>
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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D235031 Rick Macklem <rmacklem@FreeBSD.org> changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |rmacklem@FreeBSD.org --- Comment #27 from Rick Macklem <rmacklem@FreeBSD.org> --- A little off topic, but rsize,wsize will be set to a power of 2 at or below the argument. As such, rsize=3D10240,wsize=3D10240 will result in a setting of 8K (or less if the server forces it) for both of them. You can use "nfsstat -m" on the client to see what is actually being used. I can't help much, but I would suggest trying increasing powers of 2 for rsize,wsize until performance tanks. A couple of reasons smaller rsize,wsize might perform better. - TSO is broken. This can be tested by using the sysctl to disable TSO. (I suggest the generic sysctl and not a driver specific ifconfig, in case the driver config flag is broken.) - Small send or receive rings that can't handle the burst of packets/mbufs that the larger I/O size causes. A write request/receive reply will typically be a chain of size/2K + 2 mb= ufs for the sender. (Sometimes +3 depending on how the driver handles the MAC header.) The receiver will typically see this as a burst of roughly size/1500 + 1 packets making up one TCP segment. If jumbo packets are in use, all bets are off for the receive side, since at least the >4K ones can fragment the mbuf cluster pool. - Interrupt throttling. Since most NFS RPCs are small messages requiring a small reply message in the opposite direction, anything that increases latency (such as delaying interrupts assuming more packets of a stream will arrive soon) can hit NFS performance. --=20 You are receiving this mail because: You are the assignee for the bug.=
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