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Thomas Sanders
40ffd04425
The history of commits is to be used for working out which historical commit(s) (including atomic writes) caused conflicts with a currently-failing commit of a transaction. Any commit that was made before the current transaction started cannot be relevant. Therefore we never need to keep history from before the start of the longest-running transaction that is open at any given time: whenever a transaction ends (with or without a commit) then if it was the longest-running open transaction we can delete history up until start of the the next-longest-running open transaction. Some transactions might stay open for a very long time, so if any transaction exceeds conflict_max_history_seconds then we remove it from consideration in this context, and will not guarantee to keep remembering about historical commits made during such a transaction. We implement this by keeping a list of all open transactions that have not been open too long. When a transaction ends, we remove it from the list, along with any that have been open longer than the maximum; then we delete any history from before the start of the longest-running transaction remaining in the list. Reported-by: Juergen Gross <jgross@suse.com> Signed-off-by: Thomas Sanders <thomas.sanders@citrix.com> Reviewed-by: Jonathan Davies <jonathan.davies@citrix.com> Reviewed-by: Christian Lindig <christian.lindig@citrix.com>