From owner-cvs-all  Thu May  6 19:26:53 1999
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From: Kirk McKusick <mckusick@FreeBSD.org>
Date: Thu, 6 May 1999 19:26:51 -0700 (PDT)
To: cvs-committers@FreeBSD.org, cvs-all@FreeBSD.org
Subject: cvs commit: src/contrib/sys/softupdates ffs_softdep.c
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mckusick    1999/05/06 19:26:50 PDT

  Modified files:
    contrib/sys/softupdates ffs_softdep.c 
  Log:
  Severe slowdowns have been reported when creating or removing many
  files at once on a filesystem running soft updates. The root of
  the problem is that soft updates limits the amount of memory that
  may be allocated to dependency structures so as to avoid hogging
  kernel memory. The original algorithm just waited for the disk I/O
  to catch up and reduce the number of dependencies. This new code
  takes a much more aggressive approach. Basically there are two
  resources that routinely hit the limit. Inode dependencies during
  periods with a high file creation rate and file and block removal
  dependencies during periods with a high file removal rate. I have
  attacked these problems from two fronts. When the inode dependency
  limits are reached, I pick a random inode dependency, UFS_UPDATE
  it together with all the other dirty inodes contained within its
  disk block and then write that disk block. This trick usually
  clears 5-50 inode dependencies in a single disk I/O. For block and
  file removal dependencies, I pick a random directory page that has
  at least one remove pending and VOP_FSYNC its directory. That
  releases all its removal dependencies to the work queue. To further
  hasten things along, I also immediately start the work queue process
  rather than waiting for its next one second scheduled run.
  
  Revision  Changes    Path
  1.25      +290 -108  src/contrib/sys/softupdates/ffs_softdep.c


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