From: Anton Ivanov <antiv...@cisco.com> For more details see:
http://stackoverflow.com/questions/4624071/pipe-buffer-size-is-4k-or-64k The observations on that thread have been confirmed by us for UML's UBD driver. If you load UML with network IO and do disk IO at the same time the UBD IO helper thread fails to process requests fast enough. In most cases this will lead to a slowdown in disk IO as well as inability to execute new processes until the network load goes away. In some cases however it will not recover. Example - with our new high performance 1G+ network drivers a wget of 1G file from the network is a nearly guaranteed crash if it writes out to UBD. The crashes and the slowdowns are not observed with this patch - it switches the IPC to socket which does not have the pipe granularity and queue size problems. This signifies a problem with overall UBD error handling which this patch fails to fix. The workaround should be good enough for most cases. Signed-off-by: Anton Ivanov <antiv...@cisco.com> --- arch/um/drivers/ubd_kern.c | 2 +- arch/um/drivers/ubd_user.c | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-) diff --git a/arch/um/drivers/ubd_kern.c b/arch/um/drivers/ubd_kern.c index 944453a..c9a5717 100644 --- a/arch/um/drivers/ubd_kern.c +++ b/arch/um/drivers/ubd_kern.c @@ -1291,7 +1291,7 @@ static void do_ubd_request(struct request_queue *q) n = os_write_file(thread_fd, &io_req, sizeof(struct io_thread_req *)); if(n != sizeof(struct io_thread_req *)){ - if(n != -EAGAIN) + if(!((n == -EAGAIN) || (n == -ENOBUFS))) printk("write to io thread failed, " "errno = %d\n", -n); else if(list_empty(&dev->restart)) diff --git a/arch/um/drivers/ubd_user.c b/arch/um/drivers/ubd_user.c index 007b94d..f1f84a4 100644 --- a/arch/um/drivers/ubd_user.c +++ b/arch/um/drivers/ubd_user.c @@ -32,7 +32,7 @@ int start_io_thread(unsigned long sp, int *fd_out) { int pid, fds[2], err; - err = os_pipe(fds, 1, 1); + err = socketpair(AF_UNIX, SOCK_STREAM, 0, (int *) &fds); if(err < 0){ printk("start_io_thread - os_pipe failed, err = %d\n", -err); goto out; -- 1.7.10.4 ------------------------------------------------------------------------------ Subversion Kills Productivity. Get off Subversion & Make the Move to Perforce. With Perforce, you get hassle-free workflows. Merge that actually works. Faster operations. Version large binaries. Built-in WAN optimization and the freedom to use Git, Perforce or both. Make the move to Perforce. http://pubads.g.doubleclick.net/gampad/clk?id=122218951&iu=/4140/ostg.clktrk _______________________________________________ User-mode-linux-devel mailing list User-mode-linux-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/user-mode-linux-devel
