Date: Mon, 16 Apr 2018 15:20:32 +0200 From: Niels Kobschaetzki <niels@kobschaetzki.net> To: Rick Macklem <rmacklem@uoguelph.ca>, "freebsd-net@freebsd.org" <freebsd-net@freebsd.org> Subject: Re: High rate of NFS cache misses after upgrading from 10.3-prerelease to 11.1-release Message-ID: <a2c63a00-d672-e626-127b-ba0a350371e1@kobschaetzki.net> In-Reply-To: <YQBPR0101MB1042D2F0CE2575EB4F17588ADDB20@YQBPR0101MB1042.CANPRD01.PROD.OUTLOOK.COM> References: <ce3712c0-626e-c8f2-3bba-933cf359bcef@kobschaetzki.net> <YQBPR0101MB1042D2F0CE2575EB4F17588ADDB20@YQBPR0101MB1042.CANPRD01.PROD.OUTLOOK.COM>
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On 04/14/2018 03:49 AM, Rick Macklem wrote:
> If you go into ncl_getattrcache() {it's in sys/fs/nfsclient/nfs_clsubs.c}
> and add a printf() for "time_second" and "np->n_mtime.tv_sec" near the
> top, where it calculates "timeo" from it.
> Running this hacked kernel might show you if either of these fields is bogus.
> (You could then printf() "timeo" and "np->n_attrtimeo" just before the "if"
> clause that increments "attrcache_misses", which is where the cache misses
> happen to see why it is missing the cache.)
> If you could do this for the 10.3 kernel as well, this might indicate why the
> miss rate has increased?
I just checked the code to see if I can figure out where exactly I have
to put the printf(). And then I saw that there are ifdefs for
NFS_ACDEBUG which seems to be a kernel option. When I add NFS_ACDEBUG in
the config-file for the kernel, the build fails with an
/usr/src/sys/amd64/conf/ACDEBUG: unknown option "NFS_ACDEBUG"
I looked in sysctl.h and there it isn't defined. Do I do something wrong
or did this sysctl-tunable got lost at some point in time?
Can I just use this code by removing the ifdef for getting information?
Sorry, my C is not really existent, thus I have to ask :/
The parts (except the part that looks at the sysctl looks like this):
#ifdef NFS_ACDEBUG
if (nfs_acdebug>1)
printf("ncl_getattrcache: initial timeo = %d\n", timeo);
#endif
……
#ifdef NFS_ACDEBUG
if (nfs_acdebug > 2)
printf("acregmin %d; acregmax %d; acdirmin %d; acdirmax
%d\n",
nmp->nm_acregmin, nmp->nm_acregmax,
nmp->nm_acdirmin, nmp->nm_acdirmax);
if (nfs_acdebug)
printf("ncl_getattrcache: age = %d; final timeo = %d\n",
(time_second - np->n_attrstamp), timeo);
#endif
I would remove the ifdefs and the "if (nfs_acdebug …)"
Niels
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