Darren Reed wrote: > Pawel Jakub Dawidek wrote: >> Here are some updates: >> >> I was able to reproduce the panic by rsyncing big files and trying >> bonnie++ test suggested in this thread. >> >> Can you guys retry with this patch: >> >> http://people.freebsd.org/~pjd/patches/vm_kern.c.2.patch >> > > So, I have a question... > What happens if the "for (i = 0..)" is changed to "while(1)" and > the "panic" is subsequently removed? > > > It appears like the code changes the meaning of "WAIT" to "wait > for 4 seconds" then panic if it won't work. Previously, "WAIT" was > not waiting at all...whch could be described as a bug! > > If I recall correctly, ZFS caches writes and doe them in spurts and > that those spurts are spaced out more than 4 seconds. (For the > curious, do "zpool status" and observe the gap in time between > write activity.) > > If you start a large amount of I/O, it is possible that all the KVA will > be used up and ZFS will not get a chance to flush its buffers before > the 4s timer here expires. Does that sound plausible? > > Would doubling the 8 to (say) 16 be beneficial here, to at least make > the waiting span one ZFS flush out to disk? > > Darren "devil's Advocate" hat on here ... But 4 *seconds* is an entire ice-age in machine cycle terms, so.. A) I hope you are wrong about that part [1]... ;-) B) But if not... Would it not make [ equal | better | optional ] sense to look into shortening that time period? By a factor of ten comes to my mind. At least. Grant - that may mean a performance hit, hence I'd vote for 'optional' - but it should also greatly reduce, not only the likelihood of using up the alloted RAM, but of losing (quite as much of) the contents of those buffers if/as/when disaster strikes. - As it too often does, in one form or another. JM2CW Bill Hacker [1] 4 seconds 'regardless' makes more sense. i.e. flush 'em periodically just in case, even if no *known* alterations have been detected, ELSE more often depending on [ many factors ]. > > _______________________________________________ > freebsd-current_at_freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-current > To unsubscribe, send any mail to "freebsd-current-unsubscribe_at_freebsd.org"Received on Tue Oct 09 2007 - 18:13:30 UTC
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