Date: Thu, 9 Jun 2005 06:54:38 -0700 From: Alfred Perlstein <alfred@freebsd.org> To: Jeff Roberson <jeff@FreeBSD.org> Cc: cvs-src@FreeBSD.org, src-committers@FreeBSD.org, cvs-all@FreeBSD.org Subject: Re: cvs commit: src/sys/kern vfs_bio.c Message-ID: <20050609135438.GS17867@elvis.mu.org> In-Reply-To: <200506082026.j58KQ6cT052316@repoman.freebsd.org> References: <200506082026.j58KQ6cT052316@repoman.freebsd.org>
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MFC? :D * Jeff Roberson <jeff@FreeBSD.org> [050608 13:26] wrote: > jeff 2005-06-08 20:26:06 UTC > > FreeBSD src repository > > Modified files: > sys/kern vfs_bio.c > Log: > - Under heavy IO load the buf daemon can run for many hundereds of > milliseconds due to what is essentially n^2 algorithmic complexity. This > change makes the algorithm N*2 instead. This heavy processing manifested > itself as skipping in audio and video playback due to the long scheduling > latencies and contention on giant by pcm. > - flushbufqueues() is now responsible for flushing multiple buffers > rather than one at a time. This allows us to save our progress in the > list by using a sentinal. We must do the numdirtywakeup() and > waitrunningbufspace() here now rather than in buf_daemon(). > - Also add a uio_yield() after we have processed the list once for bufs > without deps and again for bufs with deps. This is to release Giant > and allow any other giant locked code to proceed. > > Tested by: Many users on current@ > Revealed by: schedgraph traces sent by Emil Mikulic & Anthony Ginepro > > Revision Changes Path > 1.487 +28 -6 src/sys/kern/vfs_bio.c -- - Alfred Perlstein - email: bright@mu.org cell: 408-480-4684
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