Significantly speed up ar(1) on UFS file systems
ClosedPublic
Actions

Authored by emaste on Jun 28 2015, 2:44 PM.

Details

Reviewers

kib
eadler

Commits

rS284928: speed up ar(1) on UFS file systems

Summary

Fault in the buffer prior to writing as a workaround for poor performance due to interaction with kernel fs deadlock avoidance code. See the comment prior to vn_io_fault_doio() in vfs_vnops.c for details of the issue.

Thanks @kib for diagnosing, providing an explanation of the issue and workaround.

Test Plan

% truncate -s 16M obj.o
% ar r out.a obj.o

Total time with stock and patched ar(1):

x ar.r284891
+ ar.patched
+----------------------------------------------------------------------+   
|+                                                                     |   
|+                                                                    x|   
|+                                                                   xx|   
|A                                                                   |A|   
+----------------------------------------------------------------------+   
    N         Min          Max        Median           Avg        Stddev   
x   3       1.307        1.321         1.315     1.3143333  0.0070237692   
+   3        0.02        0.023         0.022   0.021666667  0.0015275252   
Difference at 95.0% confidence
        -1.29267 +/- 0.0115203
        -98.3515% +/- 0.876513%
        (Student's t, pooled s = 0.00508265)

Diff Detail

Lint

Lint Skipped

Unit

Tests Skipped

Event Timeline

emaste updated this revision to Diff 6524.Jun 28 2015, 2:44 PM

emaste retitled this revision from to Significantly speed up ar(1) on UFS file systems.

emaste updated this object.

emaste edited the test plan for this revision. (Show Details)

emaste added a reviewer: kib.

emaste added subscribers: davide, dim, freebsd-toolchain-list, kib.

eadler accepted this revision.Jun 28 2015, 3:29 PM

eadler added a reviewer: eadler.

This revision is now accepted and ready to land.Jun 28 2015, 3:29 PM

kib added inline comments.Jun 29 2015, 1:02 PM

usr.bin/ar/write.c
568	It is simpler to do if (s == 0) return; for (p = buf; p < buf + s; p += page_size) p; (volatile const char *)(buf + s - 1); I do not insist.

give full path to file with comment explaining the deadlock avoidance
avoid confusing page mask manipulation and just touch the last byte explicitly

This revision now requires review to proceed.Jun 29 2015, 1:14 PM

kib accepted this revision.Jun 29 2015, 1:27 PM

kib edited edge metadata.

This revision is now accepted and ready to land.Jun 29 2015, 1:27 PM

Closed by commit rS284928: speed up ar(1) on UFS file systems (authored by emaste). · Explain WhyJun 29 2015, 1:48 PM

This revision was automatically updated to reflect the committed changes.

Revision Contents
Changeset List

Path

Size

usr.bin/

ar/

write.c

26 lines

Diff 6543

View Options

usr.bin/ar/write.c

	.\" $FreeBSD$			.\" $FreeBSD$
	Set to not build and install the enhanced			Install the traditional FreeBSD
	.Xr bc 1			.Xr bc 1
				jhbUnsubmitted Not Done Inline Actions I would maybe avoid making other changes for this commit than just the "Set to" part. Losing the Xr sections for bc and dc seems rather odd. Granted, I would rewrite this description to be something like "Use the traditional FreeBSD versions of bc(1) and dc(1) rather than the <foo> versions." where <foo> is more descriptive than just "enhanced". jhb: I would maybe avoid making other changes for this commit than just the "Set to" part. Losing…
				emasteAuthorUnsubmitted Done Inline Actions Huh, I think this must have been an accident during a rebase, I did not intend to drop these. When I first did this it was a bit of sed with manual review/touch-ups. In can incorporate feedback before this gets committed and/or we can make further improvements like this one after commit. I am also not sure what <foo> would be off hand. emaste: Huh, I think this must have been an accident during a rebase, I did not intend to drop these.
	and			and
	.Xr dc 1			.Xr dc 1
	programs instead of the traditional FreeBSD versions.			programs instead of the enahnced versions.
				emasteAuthorUnsubmitted Done Inline Actions and of course I have a typo here. corrected locally. emaste: and of course I have a typo here. corrected locally.

Significantly speed up ar(1) on UFS file systemsClosedPublicActions