On Tue, 27 May 2008 18:34:02 +0900 Hisashi Hifumi <hifumi.hisashi@xxxxxxxxxxxxx> wrote:
> When we read some part of a file through pagecache, if there is a pagecache
> of corresponding index but this page is not uptodate, read IO is issued and
> this page will be uptodate.
> I think this is good for pagesize == blocksize environment but there is room
> for improvement on pagesize != blocksize environment. Because in this case
> a page can have multiple buffers and even if a page is not uptodate, some buffers
> can be uptodate. So I suggest that when all buffers which correspond to a part
> of a file that we want to read are uptodate, use this pagecache and copy data
> from this pagecache to user buffer even if a page is not uptodate. This can
> reduce read IO and improve system throughput.
>
> v2: add new address_space_operations member is_partially_uptodate, and
> block_is_partially_uptodate was registered to ext2/3/4's aops.
> modify do_generic_file_read to use this aops callback.
> v3: use unsigned instead of unsigned long in block_is_partially_uptodate.
> cleaned up and simplified page buffer iteration code in block_is_partially_uptodate.
>
> Signed-off-by :Hisashi Hifumi <hifumi.hisashi@xxxxxxxxxxxxx>
ext4 has now gained a new set of address_space_operations:
ext4_da_aops. I put a
.is_partially_uptodate = block_is_partially_uptodate,
into there as well, but I have no clue whether it will work OK.
--
To unsubscribe from this list: send the line "unsubscribe linux-ext4" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
