Date: Wed, 25 Jun 2014 20:12:37 +0700 From: Eugene Grosbein <eugen@grosbein.net> To: Mike Tancsa <mike@sentex.net> Cc: Rick Macklem <rmacklem@uoguelph.ca>, FreeBSD-STABLE Mailing List <freebsd-stable@freebsd.org> Subject: Re: nfs slowdown (RELENG_8) Message-ID: <20140625131237.GA82922@rdtc.ru> In-Reply-To: <53A9DC0D.2000705@sentex.net> References: <2091718059.2982836.1403563319620.JavaMail.root@uoguelph.ca> <53A978D1.2000207@sentex.net> <53A987AE.8060708@sentex.net> <53A9DC0D.2000705@sentex.net>
next in thread | previous in thread | raw e-mail | index | archive | help
On Tue, Jun 24, 2014 at 04:14:05PM -0400, Mike Tancsa wrote: > But if I do > # cat /dev/zero > /nfsbackup/test > > Its down to 25Mb/s > > Now, if this were consistent across all my boxes, I would not be too > interested. > > Why is cat with a redirect so much slower, and why slower just on some > boxes and not others ?!?! cat(1) tries to determine optimal I/O block size by evaluating st_blksize of its stdout. Try to run: ktrace cat /dev/zero > /nfsbackup/test And then use kdump and see what block size does cat(1) use while writing to stdout? Eugene Grosbein
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?20140625131237.GA82922>