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contributing.html: Remove information about already implemented features

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git-svn-id: http://svn.code.sf.net/p/scst/svn/trunk@8602 d57e44dd-8a1f-0410-8b47-8ef2f437770f
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Bart Van Assche
2019-10-06 00:01:20 +00:00
parent cb73881c46
commit 3d5a5078ca
1 changed files with 0 additions and 26 deletions
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@@ -49,32 +49,6 @@
<h1>Possible SCST extensions and improvements</h1>
<A NAME="ASYNC_FILEIO"></A><h3>Asynchronous FILEIO in scst_vdisk handler</h3>
<p>At the moment scst_vdisk handler for FILEIO uses regular synchronous read/write() calls
and makes deep queue depth by using multiple threads. This is not too high performance
model of operations. It would be much better to use asynchronous I/O with not blocking
I/O calls.</p>
<p>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
(up to multiple times) increase performance of FILEIO devices.</p>
<A NAME="O_DIRECT"></A><h3>Support for O_DIRECT in scst_vdisk handler</h3>
<p>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.
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.</p>
<p>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
by pages, taken directly from dio->curr_user_address. Each such page should be referenced
by page_cache_get(). That's all.</p>
<A NAME="SG_LIMIT"></A><h3>Solve SG IO count limitation issue in pass-through mode</h3>
<p>In the pass-through mode (i.e. using the pass-through device handlers like