Messages in this thread | | | Subject | Re: [PATCH 0/3] map multiple blocks in get_block() and mpage_readpages() | From | Badari Pulavarty <> | Date | Mon, 20 Feb 2006 15:06:11 -0800 |
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On Tue, 2006-02-21 at 08:59 +1100, Nathan Scott wrote: > On Mon, Feb 20, 2006 at 01:21:27PM -0800, Badari Pulavarty wrote: > > Hi, > > Hi Badari, > > > Following patches add support to map multiple blocks in ->get_block(). > > This is will allow us to handle mapping of multiple disk blocks for > > mpage_readpages() and mpage_writepages() etc. Instead of adding new > > argument, I use "b_size" to indicate the amount of disk mapping needed > > for get_block(). And also, on success get_block() actually indicates > > the amount of disk mapping it did. > > Thanks for doing this work! > > > Now that get_block() can handle multiple blocks, there is no need > > for ->get_blocks() which was added for DIO. > > > > [PATCH 1/3] pass b_size to ->get_block() > > > > [PATCH 2/3] map multiple blocks for mpage_readpages() > > > > [PATCH 3/3] remove ->get_blocks() support > > > > I noticed decent improvements (reduced sys time) on JFS, XFS and ext3. > > (on simple "dd" read tests). > > > > (rc3.mm1) (rc3.mm1 + patches) > > real 0m18.814s 0m18.482s > > user 0m0.000s 0m0.004s > > sys 0m3.240s 0m2.912s > > > > Andrew, Could you include it in -mm tree ? > > > > Comments ? > > I've been running these patches in my development tree for awhile > and have not seen any problems. My one (possibly minor) concern > is that we pass get_block a size in units of bytes, e.g.... > > bh->b_size = 1 << inode->i_blkbits; > err = get_block(inode, block, bh, 1); > > And b_size is a u32. We have had the situation in the past where > people (I'm looking at you, Jeremy ;) have been issuing multiple- > gigabyte direct reads/writes through XFS. The syscall interface > takes an (s)size_t in bytes, which on 64 bit platforms is a 64 bit > byte count.
> I wonder if this change will end up ruining things for the lunatic > fringe issuing these kinds of IOs? Maybe the get_block call could > take a block count rather than a byte count?
Yes. I thought about it too.. I wanted to pass "block count" instead of "byte count". Right now it does ..
bh->b_size = 1 << inode->i_blkbits; call get_block();
First thing get_block() does is blocks = bh->b_size >> inode->i_blkbits;
All, the unnecessary shifting around for nothing :(
But, I ended up doing "byte count" just to avoid confusion of asking in "blocks" getting back in "bytes".
I have no problem making b_size as "size_t" to handle 64-bit. But again, if we are fiddling with buffer_head - may be its time to look at alternative to "buffer_head" with the information exactly we need for getblock() ?
Thanks, Badari
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