Date: Sat, 24 Jan 2009 09:06:50 +0000 From: Dieter <freebsd@sopwith.solgatos.com> To: freebsd-questions@FreeBSD.org Subject: Re: swap_pager complaints but not using swap Message-ID: <200901241706.RAA07150@sopwith.solgatos.com> In-Reply-To: Your message of "Sat, 24 Jan 2009 10:17:17 GMT." <497AEAAD.6020701@FreeBSD.org>
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> > AMD64 FreeBSD 7.0 2 GiB main memory > > > > My console says: > > > > login: swap_pager: indefinite wait buffer: bufobj: 0, blkno: 22, size: 4096 > > swap_pager: indefinite wait buffer: bufobj: 0, blkno: 22, size: 4096 > > swap_pager: indefinite wait buffer: bufobj: 0, blkno: 22, size: 4096 > > swap_pager: indefinite wait buffer: bufobj: 0, blkno: 22, size: 4096 > > > > pstat -sk > > Device 1K-blocks Used Avail Capacity > > /dev/ad6s10 4590208 96 4590112 0% > > > > Wow, using a whole 96K of swap. I don't see any disk related > > complaints in dmesg. > > > > Is this something to worry about? > > Yes, the system was *trying* to do swap I/O and timing out while doing so. > > Kris Whoops, I forgot to change the subject line after adding the k option to pstat. Without the k it said 0 used. And this morning it occurs to me that even if swap used was zero, it could have been trying to *start* using swap. Anyway... given this timeout explaination, I'm guessing that page/swap has to compete with user processes for disk i/o, and thus probably suffers from the same lack of fair i/o scheduling that user processes suffer from. E.g. one process doing disk i/o can lock out another process for at least several minutes, probably indefinitely. :-(
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