Re: [PATCH V8 00/33] loop: Issue O_DIRECT aio using bio_vec

From: Maxim Patlasov
Date: Wed Jul 31 2013 - 05:51:44 EST

07/31/2013 01:28 AM, Andrew Morton ÐÐÑÐÑ:
On Thu, 25 Jul 2013 12:50:26 -0500 Dave Kleikamp <dave.kleikamp@xxxxxxxxxx> wrote:

This patch series adds a kernel interface to fs/aio.c so that kernel code can
issue concurrent asynchronous IO to file systems. It adds an aio command and
file system methods which specify io memory with pages instead of userspace

This series was written to reduce the current overhead loop imposes by
performing synchronus buffered file system IO from a kernel thread. These
patches turn loop into a light weight layer that translates bios into iocbs.
Do you have any performance numbers?

Does anyone care much about loop performance? What's the value here?

OpenVZ uses loopback-device to keep per-container filesystems. We care much about overhead introduced by loop: IO-bound applications run on top of per-container filesystem shouldn't perform worse than on top of host filesystem. So the value for us is zero overhead.

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