Messages in this thread | | | Date | Mon, 11 Sep 2000 15:07:57 +0200 | From | "Andi Kleen" <> | Subject | (reiserfs) Re: More on 2.2.18pre2aa2 |
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On Mon, Sep 11, 2000 at 08:15:15AM -0400, Chris Mason wrote: > LFS changes for filldir, reiserfs_readpage, and adds limit checking in > file_write to make sure we don't go above 2GB (Andi Kleen). Also fixes > include/linux/fs.h, which does not patch cleanly for 3.5.25 because of usb. > > Note, you might see debugging messages about items moving during > copy_from_user. These are safe, but I'm leaving them in for now as I'd > like to find out why copy_from_user is suddenly scheduling much more than > it used to.
That's easy to explain. Andrea's latest aa contains some low latency patches, which add a if (current->need_resched) schedule() to copy*user to avoid bad schedule latencies for big copies. The result is that you see a lot more schedules, everytime the copy*user happens to hit the end of a time slice.
BTW, there is a another optimization that could help reiserfs a lot on SMP settings: do a unlock_kernel()/lock_kernel() around the user copies. It is quite legal to do that (you have to handle sleeping anyways in case of a page fault), and it allows CPUs to run in parallel for long running copies.
-Andi
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