Date: Sun, 19 May 2019 05:06:04 -0400 From: Cy Schubert <Cy.Schubert@cschubert.com> To: freebsd-current@freebsd.org, Konstantin Belousov <kostikbel@gmail.com>, Rick Macklem <rmacklem@uoguelph.ca> Cc: Alan Somers <asomers@freebsd.org>, "freebsd-current@FreeBSD.org" <freebsd-current@FreeBSD.org> Subject: Re: RFC w.r.t. toggling debugging on/off for mountd via a signal Message-ID: <564922E3-7BE4-498B-871A-6152A0DF9AD4@cschubert.com> In-Reply-To: <20190519085501.GL2748@kib.kiev.ua> References: <YQXPR0101MB2055B12D1AB31D4F70AF2480DD050@YQXPR0101MB2055.CANPRD01.PROD.OUTLOOK.COM> <CAOtMX2gXdjf2NhtU5Jt%2BMGg3zcONx_Gyun%2B2thy2rDYDt3FugQ@mail.gmail.com> <YQXPR0101MB205583575B42875DD298FA65DD050@YQXPR0101MB2055.CANPRD01.PROD.OUTLOOK.COM> <20190519085501.GL2748@kib.kiev.ua>
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On May 19, 2019 4:55:01 AM EDT, Konstantin Belousov <kostikbel@gmail.com> wrote: >On Sun, May 19, 2019 at 02:47:10AM +0000, Rick Macklem wrote: >> Alan Somers wrote: >> >On Sat, May 18, 2019 at 7:59 PM Rick Macklem <rmacklem@uoguelph.ca> >wrote: >> >> >> >> Hi, >> >> >> >> I've been working with Peter Errikson on a patch for mountd that >adds a new option >> >> for incremental updating of exports. This seems to be helping a >lot w.r.t. performance >> >> on an NFS server with lots (10000+) of exported file systems. >> >> >> >> I have debug syslog() calls in the code, which I/Peter think would >be worth keeping >> >> in the production code in case someone runs into problems with >this new option. >> >> >> >> As such, I'd like to have the code compiled in by default (not >only if DEBUG is defined, >> >> as mountd.c has now). I also was thinking it would be nice if the >daemon didn't need >> >> to be restarted to enable/disable the debugging output, since that >breaks NFS >> >> mounting during the restart. >> >> >> >> So, I was thinking of having the debugging output toggled on/off >via SIGUSR1. >> >> >> >> What do you think of this idea? >> >> Any other/better ways to do this? >> >> Also, would LOG_DAEMON and LOG_DEBUG sound like the correct >facility and >> >> priority for theses syslog() calls? >> >> >> >> Thanks in advance for any comments, rick >> > >> >If the debug messages aren't so verbose that they'll slow down >> >syslogd, then you can just leave them enabled all the time. syslogd >> >will filter them. However, if they're super-verbose then SIGUSR1 >> >sounds reasonable. I can't think of another daemon with runtime >> >selectable logging verbosity like that. >> Yes, these are pretty chatty. 5-10 lines for each entry in an exports >file. >> Multiply that times the number of entries. (Peter's servers are >between 20000 >> to 72000+ file systems. Not sure if he has multiple entries/file >system.) >> >> To give you a clue, without this patch, it can take 20sec->over 1min >to reload them >> when mountd gets a SIGHUP. >> >> It's just that the export file handling code is pretty convoluted, so >I think the patch >> is ok, but I won't be too surprised if someone finds a problem. > >Instead of toggling the debugging by SIGUSR1, you can make the daemon >to try to open some file by receiving the normal reload signal, e.g. >/var/run/mountd.debug. If the file is present, the debugging is >enabled. >The advantage is that the user knows what is the debugging state, >instead >of requiring to count the number of sent SIGUSR1's. > >More, in traditions of malloc(3), /var/run/mountd.debug could be a >symlink, >which is read and interpreted as some options controlling the debug. >_______________________________________________ >freebsd-current@freebsd.org mailing list >https://lists.freebsd.org/mailman/listinfo/freebsd-current >To unsubscribe, send any mail to >"freebsd-current-unsubscribe@freebsd.org" Instead of syslog() calls, DTrace probes are designed for this type of instrumentation. -- Pardon the typos and autocorrect, small keyboard in use. Cheers, Cy Schubert <Cy.Schubert@cschubert.com> FreeBSD UNIX: <cy@FreeBSD.org> Web: http://www.FreeBSD.org The need of the many outweighs the greed of the few.
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