[RFC][patch] NAND partial page read functionality
Artem Bityutskiy
dedekind at infradead.org
Thu Apr 24 06:45:53 EDT 2008
Hi,
On Thu, 2008-04-24 at 11:25 +0100, Alexey Korolev wrote:
> Oh I'm glad to hear that this patch is needful. In fact I did
> not drop it. We did some more investigations about integration subpage
> read in background. We tried to remove some drawback caused by
> invalidation of prestored page in do_read_ops function. (We have found
> that on large read requests nand subpage read causes ~10% of read performance degradation. I
> wanted to remove but changes made code ugly and saved only 5%)
Err, are you referring this chip->pagebuf cache? Have you considered
making it more complex and keep track of individual sub-pages within the
pagebuf? You say it introduces a lot of ugliness? May be you could
somehow separate this ugliness out nicely somehow?
> Also we investigated possibility to make more universal solution which includes both sub-page
> read and partial page write. As it was discussed in December. In fact the partial page write did not
> give any benefits at all as file system operates write_size. If we reduce writesize JFFS2 will write data by
> small chunks only and it will cause strong performance degradation. (it
> brings more cons than pros until serious hacks in JFFS2 will be
> implemented)
Well, in any case, if you have something for writes, this should be a
separate story.
--
Best regards,
Artem Bityutskiy (Битюцкий Артём)
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