[dm-devel] [PATCH] PROBLEM: SSD access time with dm-crypt is way too high
Christoph Hellwig
hch at infradead.org
Mon Jan 10 18:47:35 UTC 2011
On Mon, Jan 10, 2011 at 12:19:25PM -0500, Mikulas Patocka wrote:
> There are two approaches that I considered:
>
> 1. make a special work for unplug. After queuing each IO's work, cancel the
> unplug work and queue it again (so that it will always be queued as a last
> entry). Unfortunatelly, canceling a work is rather slow operation so I decided
> to not use this approach.
>
> 2. use a special pointer that points to the last IO. When the IO is finished
> and the pointer matches this IO, we know that it was the last IO and we should
> unplug. This patch implements this approach.
What about keeping a reference count of pending I/O requests in a shared
structure, with the last decrement doing the unplug?
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