On Mon, Sep 19, 2011 at 08:31:00AM -0400, Stephen Frost wrote: > * Benjamin LaHaise (bcrl@xxxxxxxxx) wrote: > > For such tables, can't Postgres track the size of the file internally? I'm > > assuming it's keeping file descriptors open on the tables it manages, in > > which case when it writes to a file to extend it, the internally stored size > > could be updated. Not making a syscall at all would scale far better than > > even a modified lseek() will perform. > > We'd have to have it in shared memory and have a lock around it, it > wouldn't be cheap at all. Yep, that makes perfect sense. After all, the kernel does basically the same thing to maintain this information; why should we have userspace duplicating the same infrastructure? I must admit, I'd never heard of this usage of lseek to get the current size of a file before; I'd assumed everybody used fstat. Given this legitimate reason for a high-frequency calling of lseek, I withdraw my earlier objection to the patch series. -- Matthew Wilcox Intel Open Source Technology Centre "Bill, look, we understand that you're interested in selling us this operating system, but compare it to ours. We can't possibly take such a retrograde step." -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
