The values in sysprocesses are cumulative since that session started. Since checkpoint runs on a system spid, it never disconnects.
Hence checkpoint has done 274125 in disk io and 418625 in cpu since the SQL Server last started.
Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability