Hi Trond, On Tue, Jul 2, 2013 at 7:02 PM, William Dauchy <william@xxxxxxxxx> wrote: > We wrote the attached tester to reproduce an issue we have with mysql on > a 3.9.8 kernel using a nfsv4 mount. > > mount options are "classic": > > rw,nosuid,nodev,noexec,relatime,vers=4.0,rsize=1048576,wsize=1048576,namlen=255,hard,proto=tcp,timeo=600,retrans=2,sec=sys,local_lock=none > > When handling a temporary file, mysql open(), then writes a bunch (say ~16MB) of data > to that file, lseeks to the start and re-reads file contents. > > With the code as attached, we see a lot of small NFS writes (1400 bytes) and > a lot of getattrs [1] and the test takes a little more than 2 seconds. > > It seems the lseek/read are serialized to the last write actually sent to the filer - > and nothing aggregates the big writes. > > If we uncomment the fsync() call, or simply close() and reopen the file, the test > completes in a few milliseconds. Same if we call sync() from any process while this > test is running. Dump shows lots of big tcp pushes, few NFS commands/answers - no > getattr in between writes. > > Is this an issue worth a dig or a known behaviour? > Can we debug this a bit further for you? > > Thanks for your time, > > [1] > (extract from the dump: > 15:56:43.681766 IP 10.0.46.65.813 > 10.0.41.39.2049: Flags [P.], seq 14399980:14401384, ack 1038253, win 24576, options [nop,nop,TS val 928349822 ecr 259987202], length 1404 > 15:56:43.685189 IP 10.0.41.39.2049 > 10.0.46.65.813: Flags [.], ack 14399980, win 32715, options [nop,nop,TS val 259987203 ecr 928349822], length 0 > 15:56:43.689131 IP 10.0.41.39.2049 > 10.0.46.65.263281194: reply ok 132 getattr NON 3 ids 0/38 sz 0 > 15:56:43.689292 IP 10.0.46.65.280058410 > 10.0.41.39.2049: 2892 getattr fh 0,0/22 > 15:56:43.689330 IP 10.0.46.65.813 > 10.0.41.39.2049: Flags [P.], seq 14404280:14405684, ack 1038389, win 24576, options [nop,nop,TS val 928349824 ecr 259987203], length 1404 > 15:56:43.690127 IP 10.0.41.39.2049 > 10.0.46.65.813: Flags [.], ack 14404280, win 32715, options [nop,nop,TS val 259987203 ecr 928349824], length 0 > 15:56:43.690651 IP 10.0.41.39.2049 > 10.0.46.65.280058410: reply ok 132 getattr NON 3 ids 0/38 sz 0 > 15:56:43.690769 IP 10.0.46.65.296835626 > 10.0.41.39.2049: 2892 getattr fh 0,0/22 > 15:56:43.690782 IP 10.0.46.65.813 > 10.0.41.39.2049: Flags [P.], seq 14408580:14409984, ack 1038525, win 24576, options [nop,nop,TS val 928349824 ecr 259987203], length 1404 > 15:56:43.691496 IP 10.0.41.39.2049 > 10.0.46.65.813: Flags [.], ack 14408580, win 32715, options [nop,nop,TS val 259987203 ecr 928349824], length 0 > 15:56:43.692970 IP 10.0.41.39.2049 > 10.0.46.65.296835626: reply ok 132 getattr NON 3 ids 0/38 sz 0 > 15:56:43.693194 IP 10.0.46.65.313612842 > 10.0.41.39.2049: 2892 getattr fh 0,0/22 > 15:56:43.693249 IP 10.0.46.65.813 > 10.0.41.39.2049: Flags [P.], seq 14412880:14414284, ack 1038661, win 24576, options [nop,nop,TS val 928349825 ecr 259987204], length 1404 > 15:56:43.693395 IP 10.0.41.39.2049 > 10.0.46.65.813: Flags [.], ack 14412880, win 32715, options [nop,nop,TS val 259987204 ecr 928349825], length 0 > 15:56:43.693644 IP 10.0.41.39.2049 > 10.0.46.65.313612842: reply ok 132 getattr NON 3 ids 0/38 sz 0 > ) Any thoughts about that? Best regards, -- William -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
