Performance improvements in XrdFileCache

[alja]

• Improve disk write performance
  Avoid multiple disk writes. Read from client in ram and then queue write task into global write list.
• Fix long held locks in XrdOfsFile
  Implement virtual ioActive() method to check if destruction has to be done in a separate task.

[alja]

Have one check to do. Temporary close.

[alja]

Cksum test OK

alja@genki xrd> xrdcp -f root://xrootd.t2.ucsd.edu//store/user/alja/data60.root origin.root
[xrootd] Total 1210.40 MB |====================| 100.00 % [54.1 MB/s]
alja@genki xrd> xrdcp -f root://xrootd-proxy.t2.ucsd.edu:7777//store/user/alja/data60.root proxy-empty.root
[xrootd] Total 1210.40 MB |====================| 100.00 % [38.0 MB/s]
alja@genki xrd> xrdcp -f root://xrootd-proxy.t2.ucsd.edu:7777//store/user/alja/data60.root proxy-cached.root
[xrootd] Total 1210.40 MB |====================| 100.00 % [116.9 MB/s]
alja@genki xrd> cksum *root
519152384 1269201040 origin.root
519152384 1269201040 proxy-cached.root
519152384 1269201040 proxy-empty.root

[alja]

600 connection test OK

Open 600 files via proxy and read them in sequence from beginning to end 2.4 MB each 10 seconds (as typical CMSSW job). This hits limit of Net traffic (1Gbs) and disk performance.

Net traffic

Disk activity

The proxy started with empty cache. Performance drops as soon as file start reading from disk.

[alja]

Reopen the pull request after completing two more test

• Test TTree::Draw() on file served from file caching proxy
• Test XrdPosixFile close -- kill 300 jobs same time