Currently ext3_get_block() only maps or allocates one block at a time. This
is quite inefficient for sequential IO workload.
I have posted a early implements a simply multiple block map and allocation
with current ext3. The basic idea is allocating the 1st block in the existing
way, and attempting to allocate the next adjacent blocks on a best effort
basis. More description about the implementation could be found here:
http://marc.theaimsgroup.com/?l=ext2-devel&m=112162230003522&w=2
The following the latest version of the patch: break the original patch into 5
patches, re-worked some logicals, and fixed some bugs. The break ups are:
[patch 1] Adding map multiple blocks at a time in ext3_get_blocks()
[patch 2] Extend ext3_get_blocks() to support multiple block allocation
[patch 3] Implement multiple block allocation in ext3-try-to-allocate
(called via ext3_new_block()).
[patch 4] Proper accounting updates in ext3_new_blocks()
[patch 5] Adjust reservation window size properly (by the given number
of blocks to allocate) before block allocation to increase the
possibility of allocating multiple blocks in a single call.
Tests done so far includes fsx,tiobench and dbench. The following numbers
collected from Direct IO tests (1G file creation/read) shows the system time
have been greatly reduced (more than 50% on my 8 cpu system) with the patches.
1G file DIO write:
2.6.15 2.6.15+patches
real 0m31.275s 0m31.161s
user 0m0.000s 0m0.000s
sys 0m3.384s 0m0.564s
1G file DIO read:
2.6.15 2.6.15+patches
real 0m30.733s 0m30.624s
user 0m0.000s 0m0.004s
sys 0m0.748s 0m0.380s
Some previous test we did on buffered IO with using multiple blocks allocation
and delayed allocation shows noticeable improvement on throughput and system
time.
This patch:
Add support of mapping multiple blocks in one call.
This is useful for DIO reads and re-writes (where blocks are already
allocated), also is in line with Christoph's proposal of using getblocks() in
mpage_readpage() or mpage_readpages().
Signed-off-by: Mingming Cao <cmm@us.ibm.com>
Cc: Badari Pulavarty <pbadari@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Linus points out that ext3_readdir's readahead only cuts in when
ext3_readdir() is operating at the very start of the directory. So for large
directories we end up performing no readahead at all and we suck.
So take it all out and use the core VM's page_cache_readahead(). This means
that ext3 directory reads will use all of readahead's dynamic sizing goop.
Note that we're using the directory's filp->f_ra to hold the readahead state,
but readahead is actually being performed against the underlying blockdev's
address_space. Fortunately the readahead code is all set up to handle this.
Tested with printk. It works. I was struggling to find a real workload which
actually cared.
(The patch also exports page_cache_readahead() to GPL modules)
Cc: "Stephen C. Tweedie" <sct@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.
Let it rip!
Mingming Cao