Re: [Scst-devel] [PATCH] vdisk_fileio: Add support for zero-copy write

[Vladislav B. <vs...@vl...>]

Hi Bart,

Bart Van Assche, on 06/22/2012 10:18 AM wrote:
> The zero-copy write implementation has been tested with ib_srpt and
> iSCSI-SCST and against the tmpfs, ext4, xfs and btrfs filesystems,
> each time with 32 SCST command processing threads.
>
> Changes compared to version three of this patch:
> - Made sure that all zero-copy work happens on thread context and not on
>    tasklet context.
> - Pages are now locked while a zero-copy read is in progress.
> - Added infrastructure to reserve a command thread for execution of a command.

Why is it needed?

> - Disabled zero-copy for bidi commands.

Also, why?

> - Introduced a new helper function vdisk_use_zero_copy().

Thanks,
Vlad