Details

Reviewers

emaste
kevlo

Commits

rS362936: Gather writes to larger chunks (MAXPHYS) instead of issuing them in

Summary

Gather writes to larger chunks (MAXPHYS) instead of issuing them in
sectors.

On my SanDisk Cruzer Blade 16GB USB stick this made formatting much faster:

x before
+ after
+--------------------------------------------------------------------------+
|+                                                                         |
|+                                                                      x  |
|+                                                                      x x|
|A                                                                      MA||
+--------------------------------------------------------------------------+
    N           Min           Max        Median           Avg        Stddev
x   3         15.89         16.38            16         16.09     0.2570992
+   3          0.32          0.37          0.35    0.34666667   0.025166115
Difference at 95.0% confidence
        -15.7433 +/- 0.414029
        -97.8455% +/- 0.25668%
        (Student's t, pooled s = 0.182665)

Diff Detail

Lint

Lint Passed

Unit

No Test Coverage

Build Status

Buildable 30727
Build 28455: arc lint + arc unit

Event Timeline

delphij created this revision.Apr 20 2020, 12:01 AM

Harbormaster completed remote builds in B30620: Diff 70794.Apr 20 2020, 12:01 AM

Tested on a hard drive; this reduced the time for format by 2/3:

x before
+ after
+------------------------------------------------------------+
|+++                                                       xx|
||A|                                                       AM|
+------------------------------------------------------------+
    N           Min           Max        Median           Avg        Stddev
x   3          7.24          7.33          7.29     7.2866667   0.045092498
+   3          2.36          2.49           2.4     2.4166667   0.066583281
Difference at 95.0% confidence
	-4.87 +/- 0.128884
	-66.8344% +/- 1.50101%
	(Student's t, pooled s = 0.0568624)

emaste added inline comments.Apr 20 2020, 6:56 PM

sbin/newfs_msdos/mkfs_msdos.c
761–762	This requires that `MAXPHYS % bpb.bpbBytesPerSec == 0` right? Do we check that anywhere?

Address reviewer comment.

Harbormaster completed remote builds in B30727: Diff 70994.Apr 26 2020, 1:26 AM

delphij marked an inline comment as done.Apr 26 2020, 1:27 AM

delphij added inline comments.

sbin/newfs_msdos/mkfs_msdos.c
761–762	No, but bpbBytesPerSec has to be greater than the buffer size (I don't think that would ever happen, though).

Round down chunksize if it's not fully aligned.

Harbormaster completed remote builds in B30728: Diff 70995.Apr 26 2020, 2:06 AM

Instead of padding the buffer, assert that they always fit as the specification requires
sector size to be one of 512, 1024, 2048 or 4096 bytes.

Harbormaster completed remote builds in B32128: Diff 74059.Jul 3 2020, 10:23 PM

ministat graph for time savings.

x before
+ after
+--------------------------------------------------------------------------+
|+                                                                         |
|+                                                                      x  |
|+                                                                      x x|
|A                                                                      MA||
+--------------------------------------------------------------------------+
    N           Min           Max        Median           Avg        Stddev
x   3         15.89         16.38            16         16.09     0.2570992
+   3          0.32          0.37          0.35    0.34666667   0.025166115
Difference at 95.0% confidence
	-15.7433 +/- 0.414029
	-97.8455% +/- 0.25668%
	(Student's t, pooled s = 0.182665)