Date: Sun, 20 Oct 2002 00:19:30 -0700 From: David Schultz <dschultz@uclink.Berkeley.EDU> To: Dan Nelson <dnelson@allantgroup.com> Cc: Terry Lambert <tlambert2@mindspring.com>, Brooks Davis <brooks@one-eyed-alien.net>, hackers@FreeBSD.ORG Subject: Re: adding a delay before background fsck Message-ID: <20021020071930.GA24660@HAL9000.homeunix.com> In-Reply-To: <20021020065635.GB66757@dan.emsphone.com> References: <20021019223250.A14311@Odin.AC.HMC.Edu> <3DB25030.20DC0624@mindspring.com> <20021020065635.GB66757@dan.emsphone.com>
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Thus spake Dan Nelson <dnelson@allantgroup.com>: > In the last episode (Oct 19), Terry Lambert said: > > Brooks Davis wrote: > > > Please comment on the following patch to add a delay before > > > starting background fsck. The issues this addresses is that it > > > takes a long time to start X or other large apps like mozilla while > > > a background fsck is running (at least on my laptop). Once they > > > are up and in cache, performance is slightly bumpy, but acceptable. > > > Thus, being able to set a delay (I use 120s) to allow those > > > applications to be started, makes background fsck much more useful. > > > I suspect this feature would also be useful in aiding recover on > > > servers. > > > > Shouldn't running it at idleprio "just work"? > > Unfortunately, priorities do not apply to I/O. `Nice' values *do* apply to I/O in -CURRENT. Specifically, if a process with a positive nice value attempts to do disk I/O while there are other outstanding requests, it is put to sleep for p_nice/HZ seconds. I think this feature was added specifically for background fsck. If performance is a problem, perhaps it is the nice value that needs to be tuned. See Kirk's BSDCon paper on snapshots for details. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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