Ivan Voras <ivoras@xxxxxxxxxxx> writes: > On 10/04/10 20:49, Josh Berkus wrote: >>> The other major bottleneck they ran into was a kernel one: reading from >>> the heap file requires a couple lseek operations, and Linux acquires a >>> mutex on the inode to do that. > Hmmm... lseek? As in "lseek() then read() or write()" idiom? It AFAIK > cannot be fixed since you're modifying the global "strean position" > variable and something has got to lock that. Um, there is no "global stream position" associated with an inode. A file position is associated with an open-file descriptor. If Josh quoted the problem correctly, the issue is that the kernel is locking a file's inode (which may be referenced by quite a lot of file descriptors) in order to change the state of one file descriptor. It sure sounds like a possible source of contention to me. regards, tom lane -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
