diff --git a/www/contributing.html b/www/contributing.html index def6cf2f1..1c9cf66d9 100644 --- a/www/contributing.html +++ b/www/contributing.html @@ -59,14 +59,17 @@

In the user space native AIO is available for many years, but only very recently ability to use it was added in the kernel. Changing FILEIO to use the new interface should significantly - (multiple times) increase performance of FILEIO devices.

+ (up to multiple times) increase performance of FILEIO devices.

Support for O_DIRECT in scst_vdisk handler

At the moment, scst_vdisk handler doesn't support O_DIRECT option and possibility to set it was disabled. This limitation caused by Linux kernel expectation that memory supplied to - read() and write() functions with O_DIRECT flag is mapped to some user space application.

- + read() and write() functions with O_DIRECT flag is mapped to some user space application. + Having O_DIRECT together with above asynchronous FILEIO would be another significant + performance boost for modern solid state devices. For instance, in fio utility + direct AIO long ago proven to be the fastest way to benchmark storage.

+

It is relatively easy to remove that limitation. Function dio_refill_pages() should be modified to check before calling get_user_pages() if current->mm is not NULL. If it is NULL, then, instead of calling get_user_pages(), dio->pages should be filled