Date: Wed, 17 Feb 2010 20:15:50 +0100 From: Harald Schmalzbauer <h.schmalzbauer@omnilan.de> To: Chuck Swiger <cswiger@mac.com> Cc: freebsd-stable@freebsd.org Subject: Re: best practice to watch TCP parms of established sockets Message-ID: <4B7C4066.5040006@omnilan.de> In-Reply-To: <70CD649D-7659-4CE2-A16C-49B8C891CB5B@mac.com> References: <4B7C1365.9070806@omnilan.de> <70CD649D-7659-4CE2-A16C-49B8C891CB5B@mac.com>
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This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --------------enigC69D5F768CE3065A98DEFFF4 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Am 17.02.2010 19:56, schrieb Chuck Swiger: > Hi-- >=20 > On Feb 17, 2010, at 8:03 AM, Harald Schmalzbauer wrote: >> while doing some ZFS tests with RELENG_8 I recognized a mysterious per= formace drop after an hour uptime. >> Now my first idea is to compare MSS and windows sizes before and after= the performance drop. >> How do I best capture them? tdpcump? It's GbE linkspeed... >=20 > It seems more likely that ZFS is running into slowdowns from resource c= ontention, memory fragmentation, etc than your network would suddenly dro= p out, but tcpdump -w outfile.pcap is a good method of looking.... Thanks, but fisrt tests showed that ZFS is not causing the slowdown. I noticed that disabling window scaling (rfc1323) speeds up the transfer rate by factor 1.5 (rsync transfers start at 75MB/s, settling down at 55MB/s, while rfc1323 enabled leads to half the windows size (8k) and rsync transfers start with 50MB/s and go down to 38MB/s). Now I'm going through "internet core protocols" becaus it's been a long time ago I had such a deep look into TCP/IP and I don't have all the TCP sequences and options in memory. Not falsified yet, but as soon as I open a second high data rate transfer, simultanious to the rsync, (a smb transfer of a large file for example) the shared speed will stay at that level, even if the second transfer has finbished. Meaning: I can rsync with 50MB/s. If I simultaniously transfer another file via samba, I have two 25MB/s transfers. From that moment on I can never get more that 25MB/s per transfer until I reboot the machine. Like mentioned eralier, I first have to refresh some networking basics, but expect some more results soon. Thanks, -Harry --------------enigC69D5F768CE3065A98DEFFF4 Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.12 (MingW32) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/ iEYEARECAAYFAkt8QG8ACgkQLDqVQ9VXb8izsgCgjIP9AQ8y50fxYNFaYsIUfPmA v+IAoJ3UCyzamZ0JR5kDBdbNtYBX/kDq =id9Q -----END PGP SIGNATURE----- --------------enigC69D5F768CE3065A98DEFFF4--
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