Messages in this thread | | | Date | Fri, 11 Jul 2008 16:39:01 -0700 | From | Andrew Morton <> | Subject | Re: [PATCH] VFS: Pagecache usage optimization onpagesize!=blocksize environment |
| |
On Tue, 27 May 2008 18:34:02 +0900 Hisashi Hifumi <hifumi.hisashi@oss.ntt.co.jp> 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@oss.ntt.co.jp>
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.
| |