Hi Andrew,
Here is my first pass at making use of PageMappedToDisk() to avoid
ext3 prepare_write/commit_write handling + journaling.
I see significant improvements with my micro benchmarks for over-write
(pages again & again) case. Does this look right to you ?
2.6.16-rc6 2.6.16-rc6+patch
real 0m6.606s 0m3.705s
user 0m0.124s 0m0.108s
sys 0m6.456s 0m3.600s
Thanks,
Badari
Make use of PageMappedToDisk(page) to find out if we need to
block allocation and skip the calls to it, if not needed.
When we are not doing block allocation, also avoid calls
to journal start and adding buffers to transaction.
Signed-off-by: Badari Pulavarty <[email protected]>
Index: linux-2.6.16-rc6/fs/buffer.c
===================================================================
--- linux-2.6.16-rc6.orig/fs/buffer.c 2006-03-11 14:12:55.000000000 -0800
+++ linux-2.6.16-rc6/fs/buffer.c 2006-03-15 13:05:26.000000000 -0800
@@ -2051,8 +2051,10 @@ static int __block_commit_write(struct i
* the next read(). Here we 'discover' whether the page went
* uptodate as a result of this (potentially partial) write.
*/
- if (!partial)
+ if (!partial) {
SetPageUptodate(page);
+ SetPageMappedToDisk(page);
+ }
return 0;
}
Index: linux-2.6.16-rc6/fs/ext3/inode.c
===================================================================
--- linux-2.6.16-rc6.orig/fs/ext3/inode.c 2006-03-11 14:12:55.000000000 -0800
+++ linux-2.6.16-rc6/fs/ext3/inode.c 2006-03-15 13:09:14.000000000 -0800
@@ -999,6 +999,13 @@ static int ext3_prepare_write(struct fil
handle_t *handle;
int retries = 0;
+
+ /*
+ * If the page is already mapped to disk and we are not
+ * journalling the data - there is nothing to do.
+ */
+ if (PageMappedToDisk(page) && !ext3_should_journal_data(inode))
+ return 0;
retry:
handle = ext3_journal_start(inode, needed_blocks);
if (IS_ERR(handle)) {
@@ -1059,8 +1066,14 @@ static int ext3_ordered_commit_write(str
struct inode *inode = page->mapping->host;
int ret = 0, ret2;
- ret = walk_page_buffers(handle, page_buffers(page),
- from, to, NULL, ext3_journal_dirty_data);
+ /*
+ * If the page is already mapped to disk, we won't have
+ * a handle - which means no metadata updates are needed.
+ * So, no need to add buffers to the transaction.
+ */
+ if (handle)
+ ret = walk_page_buffers(handle, page_buffers(page),
+ from, to, NULL, ext3_journal_dirty_data);
if (ret == 0) {
/*
@@ -1075,9 +1088,11 @@ static int ext3_ordered_commit_write(str
EXT3_I(inode)->i_disksize = new_i_size;
ret = generic_commit_write(file, page, from, to);
}
- ret2 = ext3_journal_stop(handle);
- if (!ret)
- ret = ret2;
+ if (handle) {
+ ret2 = ext3_journal_stop(handle);
+ if (!ret)
+ ret = ret2;
+ }
return ret;
}
@@ -1098,9 +1113,11 @@ static int ext3_writeback_commit_write(s
else
ret = generic_commit_write(file, page, from, to);
- ret2 = ext3_journal_stop(handle);
- if (!ret)
- ret = ret2;
+ if (handle) {
+ ret2 = ext3_journal_stop(handle);
+ if (!ret)
+ ret = ret2;
+ }
return ret;
}
@@ -1278,6 +1295,14 @@ static int ext3_ordered_writepage(struct
if (ext3_journal_current_handle())
goto out_fail;
+ /*
+ * If the page is mapped to disk, just do the IO
+ */
+ if (PageMappedToDisk(page)) {
+ ret = block_write_full_page(page, ext3_get_block, wbc);
+ goto out;
+ }
+
handle = ext3_journal_start(inode, ext3_writepage_trans_blocks(inode));
if (IS_ERR(handle)) {
@@ -1318,6 +1343,7 @@ static int ext3_ordered_writepage(struct
err = ext3_journal_stop(handle);
if (!ret)
ret = err;
+out:
return ret;
out_fail:
@@ -1337,10 +1363,13 @@ static int ext3_writeback_writepage(stru
if (ext3_journal_current_handle())
goto out_fail;
- handle = ext3_journal_start(inode, ext3_writepage_trans_blocks(inode));
- if (IS_ERR(handle)) {
- ret = PTR_ERR(handle);
- goto out_fail;
+ if (!PageMappedToDisk(page)) {
+ handle = ext3_journal_start(inode,
+ ext3_writepage_trans_blocks(inode));
+ if (IS_ERR(handle)) {
+ ret = PTR_ERR(handle);
+ goto out_fail;
+ }
}
if (test_opt(inode->i_sb, NOBH))
@@ -1348,9 +1377,11 @@ static int ext3_writeback_writepage(stru
else
ret = block_write_full_page(page, ext3_get_block, wbc);
- err = ext3_journal_stop(handle);
- if (!ret)
- ret = err;
+ if (handle) {
+ err = ext3_journal_stop(handle);
+ if (!ret)
+ ret = err;
+ }
return ret;
out_fail:
-
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