GFS2: Speed up gfs2_rbm_from_block
This patch is a rewrite of function gfs2_rbm_from_block. Rather than
looping to find the right bitmap, the code now does a few simple
math calculations.
I compared the performance of both algorithms side by side and the new
algorithm is noticeably faster. Sample instrumentation output from a
"fast" machine:
5 million calls: millisec spent: Orig: 166 New: 113
5 million calls: millisec spent: Orig: 189 New: 114
In addition, I ran postmark (on a somewhat slowr CPU) before the after
the new algorithm was put in place and postmark showed a decent
improvement:
Before the new algorithm:
-------------------------
Time:
645 seconds total
584 seconds of transactions (171 per second)
Files:
150087 created (232 per second)
Creation alone: 100000 files (2083 per second)
Mixed with transactions: 50087 files (85 per second)
49995 read (85 per second)
49991 appended (85 per second)
150087 deleted (232 per second)
Deletion alone: 100174 files (7705 per second)
Mixed with transactions: 49913 files (85 per second)
Data:
273.42 megabytes read (434.08 kilobytes per second)
852.13 megabytes written (1.32 megabytes per second)
With the new algorithm:
-----------------------
Time:
599 seconds total
530 seconds of transactions (188 per second)
Files:
150087 created (250 per second)
Creation alone: 100000 files (1886 per second)
Mixed with transactions: 50087 files (94 per second)
49995 read (94 per second)
49991 appended (94 per second)
150087 deleted (250 per second)
Deletion alone: 100174 files (6260 per second)
Mixed with transactions: 49913 files (94 per second)
Data:
273.42 megabytes read (467.42 kilobytes per second)
852.13 megabytes written (1.42 megabytes per second)
Signed-off-by: Bob Peterson <[email protected]>
Signed-off-by: Steven Whitehouse <[email protected]>
diff --git a/fs/gfs2/rgrp.c b/fs/gfs2/rgrp.c
index 38fe18f..669b89b 100644
--- a/fs/gfs2/rgrp.c
+++ b/fs/gfs2/rgrp.c
@@ -251,22 +251,25 @@
static int gfs2_rbm_from_block(struct gfs2_rbm *rbm, u64 block)
{
u64 rblock = block - rbm->rgd->rd_data0;
- u32 goal = (u32)rblock;
- int x;
+ u32 x;
if (WARN_ON_ONCE(rblock > UINT_MAX))
return -EINVAL;
if (block >= rbm->rgd->rd_data0 + rbm->rgd->rd_data)
return -E2BIG;
- for (x = 0; x < rbm->rgd->rd_length; x++) {
- rbm->bi = rbm->rgd->rd_bits + x;
- if (goal < (rbm->bi->bi_start + rbm->bi->bi_len) * GFS2_NBBY) {
- rbm->offset = goal - (rbm->bi->bi_start * GFS2_NBBY);
- break;
- }
- }
+ rbm->bi = rbm->rgd->rd_bits;
+ rbm->offset = (u32)(rblock);
+ /* Check if the block is within the first block */
+ if (rbm->offset < (rbm->bi->bi_start + rbm->bi->bi_len) * GFS2_NBBY)
+ return 0;
+ /* Adjust for the size diff between gfs2_meta_header and gfs2_rgrp */
+ rbm->offset += (sizeof(struct gfs2_rgrp) -
+ sizeof(struct gfs2_meta_header)) * GFS2_NBBY;
+ x = rbm->offset / rbm->rgd->rd_sbd->sd_blocks_per_bitmap;
+ rbm->offset -= x * rbm->rgd->rd_sbd->sd_blocks_per_bitmap;
+ rbm->bi += x;
return 0;
}
