Patchwork [2,of,2,V2] changelog: disable delta chains

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Submitter Gregory Szorc
Date Oct. 2, 2016, 5:33 p.m.
Message ID <20c0d05c4f8e9f6f0c64.1475429590@ubuntu-vm-main>
Download mbox | patch
Permalink /patch/16822/
State Superseded
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Gregory Szorc - Oct. 2, 2016, 5:33 p.m.
# HG changeset patch
# User Gregory Szorc <gregory.szorc@gmail.com>
# Date 1475429177 25200
#      Sun Oct 02 10:26:17 2016 -0700
# Node ID 20c0d05c4f8e9f6f0c64cf17cd8fb89530ba0af3
# Parent  b4ca569d38c9e35f542b90868f86247ad8844b4c
changelog: disable delta chains

This patch disables delta chains on changelogs. After this patch, new
entries on changelogs - including existing changelogs - will be stored
as the fulltext of that data (likely compressed). No delta computation
will be performed.

An overview of delta chains and data justifying this change follows.

Revlogs try to store entries as a delta against a previous entry (either
a parent revision in the case of generaldelta or the previous physical
revision when not using generaldelta). Most of the time this is the
correct thing to do: it frequently results in less CPU usage and smaller
storage.

Delta chains are most effective when the base revision being deltad
against is similar to the current data. This tends to occur naturally
for manifests and file data, since only small parts of each tend to
change with each revision. Changelogs, however, are a different story.

Changelog entries represent changesets/commits. And unless commits in a
repository are homogonous (same author, changing same files, similar
commit messages, etc), a delta from one entry to the next tends to be
relatively large compared to the size of the entry. This means that
delta chains tend to be short. How short? Here is the full vs delta
revision breakdown on some real world repos:

Repo             % Full    % Delta   Max Length
hg                45.8       54.2        6
mozilla-central   42.4       57.6        8
mozilla-unified   42.5       57.5       17
pypy              46.1       53.9        6
python-zstandard  46.1       53.9        3

(I threw in python-zstandard as an example of a repo that is homogonous.
It contains a small Python project with changes all from the same
author.)

Contrast this with the manifest revlog for these repos, where 99+% of
revisions are deltas and delta chains run into the thousands.

So delta chains aren't as useful on changelogs. But even a short delta
chain may provide benefits. Let's measure that.

Delta chains may require less CPU to read revisions if the CPU time
spent reading smaller deltas is less than the CPU time used to
decompress larger individual entries. We can measure this via
`hg perfrevlog -c -d 1` to iterate a revlog to resolve each revision's
fulltext. Here are the results of that command on a repo using delta
chains in its changelog and on a repo without delta chains:

hg (forward)
! wall 0.407008 comb 0.410000 user 0.410000 sys 0.000000 (best of 25)
! wall 0.390061 comb 0.390000 user 0.390000 sys 0.000000 (best of 26)

hg (reverse)
! wall 0.515221 comb 0.520000 user 0.520000 sys 0.000000 (best of 19)
! wall 0.400018 comb 0.400000 user 0.390000 sys 0.010000 (best of 25)

mozilla-central (forward)
! wall 4.508296 comb 4.490000 user 4.490000 sys 0.000000 (best of 3)
! wall 4.370222 comb 4.370000 user 4.350000 sys 0.020000 (best of 3)

mozilla-central (reverse)
! wall 5.758995 comb 5.760000 user 5.720000 sys 0.040000 (best of 3)
! wall 4.346503 comb 4.340000 user 4.320000 sys 0.020000 (best of 3)

mozilla-unified (forward)
! wall 4.957088 comb 4.950000 user 4.940000 sys 0.010000 (best of 3)
! wall 4.660528 comb 4.650000 user 4.630000 sys 0.020000 (best of 3)

mozilla-unified (reverse)
! wall 6.119827 comb 6.110000 user 6.090000 sys 0.020000 (best of 3)
! wall 4.675136 comb 4.670000 user 4.670000 sys 0.000000 (best of 3)

pypy (forward)
! wall 1.231122 comb 1.240000 user 1.230000 sys 0.010000 (best of 8)
! wall 1.164896 comb 1.160000 user 1.160000 sys 0.000000 (best of 9)

pypy (reverse)
! wall 1.467049 comb 1.460000 user 1.460000 sys 0.000000 (best of 7)
! wall 1.160200 comb 1.170000 user 1.160000 sys 0.010000 (best of 9)

The data clearly shows that it takes less wall and CPU time to resolve
revisions when there are no delta chains in the changelogs, regardless
of the direction of traversal. Furthermore, not using a delta chain
means that fulltext resolution in reverse is as fast as iterating
forward. So not using delta chains on the changelog is a clear CPU win
for reading operations.

An example of a user-visible operation showing this speed-up is revset
evaluation. Here are results for
`hg perfrevset 'author(gps) or author(mpm)'`:

hg
! wall 1.655506 comb 1.660000 user 1.650000 sys 0.010000 (best of 6)
! wall 1.612723 comb 1.610000 user 1.600000 sys 0.010000 (best of 7)

mozilla-central
! wall 17.629826 comb 17.640000 user 17.600000 sys 0.040000 (best of 3)
! wall 17.311033 comb 17.300000 user 17.260000 sys 0.040000 (best of 3)

What about 00changelog.i size?

Repo                Delta Chains     No Delta Chains
hg                    7,033,250         6,976,771
mozilla-central      82,978,748        81,574,623
mozilla-unified      88,112,349        86,702,162
pypy                 20,740,699        20,659,741

The data shows that removing delta chains from the changelog makes the
changelog smaller.

Delta chains are also used during changegroup generation. This
operation essentially converts a series of revisions to one large
delta chain. And changegroup generation is smart: if the delta in
the revlog matches what the changegroup is emitting, it will reuse
the delta instead of recalculating it. We can measure the impact
removing changelog delta chains has on changegroup generation via
`hg perfchangegroupchangelog`:

hg
! wall 1.589245 comb 1.590000 user 1.590000 sys 0.000000 (best of 7)
! wall 1.788060 comb 1.790000 user 1.790000 sys 0.000000 (best of 6)

mozilla-central
! wall 17.382585 comb 17.380000 user 17.340000 sys 0.040000 (best of 3)
! wall 20.161357 comb 20.160000 user 20.120000 sys 0.040000 (best of 3)

mozilla-unified
! wall 18.722839 comb 18.720000 user 18.680000 sys 0.040000 (best of 3)
! wall 21.168075 comb 21.170000 user 21.130000 sys 0.040000 (best of 3)

pypy
! wall 4.828317 comb 4.830000 user 4.820000 sys 0.010000 (best of 3)
! wall 5.415455 comb 5.420000 user 5.410000 sys 0.010000 (best of 3)

The data shows eliminating delta chains makes the changelog part of
changegroup generation slower. This is expected since we now have to
compute deltas for revisions where we could recycle the delta before.

It is worth putting this regression into context of overall changegroup
times. Here is the rough total CPU time spent in changegroup generation
for various repos while using delta chains on the changelog:

Repo              CPU Time (s)    CPU Time w/ compression
hg                  4.50              7.05
mozilla-central   111.1             222.0
pypy               28.68             75.5

Before compression, removing delta chains from the changegroup adds
~4.4% overhead to hg changegroup generation, 1.3% to mozilla-central,
and 2.0% to pypy. When you factor in zlib compression, these percentages
are roughly divided by 2.

While the increased CPU usage for changegroup generation is unfortunate,
I think it is acceptable because the percentage is small, server
operators (those likely impacted most by this) have other mechanisms
to mitigate CPU consumption (namely reducing zlib compression level and
pre-generated clone bundles), and because there is room to optimize this
in the future. For example, we could use the nullid is the base revision,
effectively encoding the full revision for each entry in the changelog.
When doing this, `hg perfchangegroupchangelog` nearly halves:

mozilla-unified
! wall 21.168075 comb 21.170000 user 21.130000 sys 0.040000 (best of 3)
! wall 11.196461 comb 11.200000 user 11.190000 sys 0.010000 (best of 3)

This looks very promising as a future optimization opportunity.
timeless - Oct. 5, 2016, 1:27 a.m.
Are repositories locally compatible with older versions of hg?

I'm pretty sure from what you've written that they're wire compatible with
older versions.
Gregory Szorc - Oct. 5, 2016, 2:25 p.m.
On Tue, Oct 4, 2016 at 6:27 PM, timeless <timeless@gmail.com> wrote:

> Are repositories locally compatible with older versions of hg?
>
> I'm pretty sure from what you've written that they're wire compatible with
> older versions.
>
Yes. This commit changes the default behavior of the revlog to force a new
delta chain (store a full revision instead of possibly a delta) for each
revision instead of using a heuristic. It should not change wire protocol
behavior. Although a few tests did change the wire protocol subtly, so I
need to figure out what's going on there.
Ryan McElroy - Oct. 5, 2016, 3:39 p.m.
On 10/2/2016 6:33 PM, Gregory Szorc wrote:
> # HG changeset patch
> # User Gregory Szorc <gregory.szorc@gmail.com>
> # Date 1475429177 25200
> #      Sun Oct 02 10:26:17 2016 -0700
> # Node ID 20c0d05c4f8e9f6f0c64cf17cd8fb89530ba0af3
> # Parent  b4ca569d38c9e35f542b90868f86247ad8844b4c
> changelog: disable delta chains
>
> This patch disables delta chains on changelogs. After this patch, new
> entries on changelogs - including existing changelogs - will be stored
> as the fulltext of that data (likely compressed). No delta computation
> will be performed.

I always wondered why we attempted delta compression on changelogs at 
all. I'm impressed that there are even delta chains of 7 in these repos 
(but I guess if you search hard enough for deltas, you might find some). 
In short, this change makes sense to me!

> Delta chains are also used during changegroup generation. This
> operation essentially converts a series of revisions to one large
> delta chain. And changegroup generation is smart: if the delta in
> the revlog matches what the changegroup is emitting, it will reuse
> the delta instead of recalculating it. We can measure the impact
> removing changelog delta chains has on changegroup generation via
> `hg perfchangegroupchangelog`:

Is requiring deltas at this stage required? How much work is your 
proposed optimization of always deltaing against the null commit (or to 
put it another way, why isn't that optimization included in this series?)

Thanks also for the great write-up!
Pierre-Yves David - Oct. 5, 2016, 11:54 p.m.
On 10/05/2016 04:25 PM, Gregory Szorc wrote:
>
> On Tue, Oct 4, 2016 at 6:27 PM, timeless <timeless@gmail.com
> <mailto:timeless@gmail.com>> wrote:
>
>     Are repositories locally compatible with older versions of hg?
>
>     I'm pretty sure from what you've written that they're wire
>     compatible with older versions.
>
> Yes. This commit changes the default behavior of the revlog to force a
> new delta chain (store a full revision instead of possibly a delta) for
> each revision instead of using a heuristic. It should not change wire
> protocol behavior. Although a few tests did change the wire protocol
> subtly, so I need to figure out what's going on there.

For the records, this tests changes is the main reason why I've not 
attempted to pushed this yet. They might be legit change, but we kind of 
need to be able to explain them to be sure of that.

Cheers,
Gregory Szorc - Oct. 6, 2016, 5:07 a.m.
> On Oct 5, 2016, at 17:39, Ryan McElroy <rm@fb.com> wrote:
> 
>> On 10/2/2016 6:33 PM, Gregory Szorc wrote:
>> # HG changeset patch
>> # User Gregory Szorc <gregory.szorc@gmail.com>
>> # Date 1475429177 25200
>> #      Sun Oct 02 10:26:17 2016 -0700
>> # Node ID 20c0d05c4f8e9f6f0c64cf17cd8fb89530ba0af3
>> # Parent  b4ca569d38c9e35f542b90868f86247ad8844b4c
>> changelog: disable delta chains
>> 
>> This patch disables delta chains on changelogs. After this patch, new
>> entries on changelogs - including existing changelogs - will be stored
>> as the fulltext of that data (likely compressed). No delta computation
>> will be performed.
> 
> I always wondered why we attempted delta compression on changelogs at all. I'm impressed that there are even delta chains of 7 in these repos (but I guess if you search hard enough for deltas, you might find some). In short, this change makes sense to me!
> 
>> Delta chains are also used during changegroup generation. This
>> operation essentially converts a series of revisions to one large
>> delta chain. And changegroup generation is smart: if the delta in
>> the revlog matches what the changegroup is emitting, it will reuse
>> the delta instead of recalculating it. We can measure the impact
>> removing changelog delta chains has on changegroup generation via
>> `hg perfchangegroupchangelog`:
> 
> Is requiring deltas at this stage required? How much work is your proposed optimization of always deltaing against the null commit (or to put it another way, why isn't that optimization included in this series?)

It shouldn't be too difficult - just time consuming. We don't have terrific tools around measuring changegroup performance and size. Then we have to consider impact on legacy clients that would re-delta the changegroup entries. I figured it best to deal with the subject later.

> 
> Thanks also for the great write-up!
> _______________________________________________
> Mercurial-devel mailing list
> Mercurial-devel@mercurial-scm.org
> https://www.mercurial-scm.org/mailman/listinfo/mercurial-devel

Patch

diff --git a/mercurial/changelog.py b/mercurial/changelog.py
--- a/mercurial/changelog.py
+++ b/mercurial/changelog.py
@@ -258,16 +258,22 @@  class changelogrevision(object):
 class changelog(revlog.revlog):
     def __init__(self, opener):
         revlog.revlog.__init__(self, opener, "00changelog.i",
                                checkambig=True)
         if self._initempty:
             # changelogs don't benefit from generaldelta
             self.version &= ~revlog.REVLOGGENERALDELTA
             self._generaldelta = False
+
+        # Delta chains for changelogs tend to be very small because entries
+        # tend to be small and don't delta well with each. So disable delta
+        # chains.
+        self._storedeltachains = False
+
         self._realopener = opener
         self._delayed = False
         self._delaybuf = None
         self._divert = False
         self.filteredrevs = frozenset()
 
     def tip(self):
         """filtered version of revlog.tip"""
diff --git a/tests/test-acl.t b/tests/test-acl.t
--- a/tests/test-acl.t
+++ b/tests/test-acl.t
@@ -1504,17 +1504,17 @@  No branch acls specified
   acl: path access granted: "ef1ea85a6374"
   acl: branch access granted: "f9cafe1212c8" on branch "default"
   acl: path access granted: "f9cafe1212c8"
   acl: branch access granted: "911600dab2ae" on branch "default"
   acl: path access granted: "911600dab2ae"
   acl: branch access granted: "e8fc755d4d82" on branch "foobar"
   acl: path access granted: "e8fc755d4d82"
   updating the branch cache
-  bundle2-input-part: total payload size 2101
+  bundle2-input-part: total payload size 2139
   bundle2-input-part: "pushkey" (params: 4 mandatory) supported
   pushing key for "phases:911600dab2ae7a9baff75958b84fe606851ce955"
   bundle2-input-part: "pushkey" (params: 4 mandatory) supported
   pushing key for "phases:e8fc755d4d8217ee5b0c2bb41558c40d43b92c01"
   bundle2-input-bundle: 4 parts total
   bundle2-output-bundle: "HG20", 3 parts total
   bundle2-output-part: "reply:changegroup" (advisory) (params: 0 advisory) empty payload
   bundle2-output-part: "reply:pushkey" (params: 0 advisory) empty payload
@@ -1590,17 +1590,17 @@  Branch acl deny test
   acl: acl.deny not enabled
   acl: branch access granted: "ef1ea85a6374" on branch "default"
   acl: path access granted: "ef1ea85a6374"
   acl: branch access granted: "f9cafe1212c8" on branch "default"
   acl: path access granted: "f9cafe1212c8"
   acl: branch access granted: "911600dab2ae" on branch "default"
   acl: path access granted: "911600dab2ae"
   error: pretxnchangegroup.acl hook failed: acl: user "astro" denied on branch "foobar" (changeset "e8fc755d4d82")
-  bundle2-input-part: total payload size 2101
+  bundle2-input-part: total payload size 2139
   bundle2-input-bundle: 4 parts total
   transaction abort!
   rollback completed
   abort: acl: user "astro" denied on branch "foobar" (changeset "e8fc755d4d82")
   no rollback information available
   2:fb35475503ef
   
 
@@ -1658,17 +1658,17 @@  Branch acl empty allow test
   added 4 changesets with 4 changes to 4 files (+1 heads)
   calling hook pretxnchangegroup.acl: hgext.acl.hook
   acl: checking access for user "astro"
   acl: acl.allow.branches enabled, 0 entries for user astro
   acl: acl.deny.branches not enabled
   acl: acl.allow not enabled
   acl: acl.deny not enabled
   error: pretxnchangegroup.acl hook failed: acl: user "astro" not allowed on branch "default" (changeset "ef1ea85a6374")
-  bundle2-input-part: total payload size 2101
+  bundle2-input-part: total payload size 2139
   bundle2-input-bundle: 4 parts total
   transaction abort!
   rollback completed
   abort: acl: user "astro" not allowed on branch "default" (changeset "ef1ea85a6374")
   no rollback information available
   2:fb35475503ef
   
 
@@ -1728,17 +1728,17 @@  Branch acl allow other
   added 4 changesets with 4 changes to 4 files (+1 heads)
   calling hook pretxnchangegroup.acl: hgext.acl.hook
   acl: checking access for user "astro"
   acl: acl.allow.branches enabled, 0 entries for user astro
   acl: acl.deny.branches not enabled
   acl: acl.allow not enabled
   acl: acl.deny not enabled
   error: pretxnchangegroup.acl hook failed: acl: user "astro" not allowed on branch "default" (changeset "ef1ea85a6374")
-  bundle2-input-part: total payload size 2101
+  bundle2-input-part: total payload size 2139
   bundle2-input-bundle: 4 parts total
   transaction abort!
   rollback completed
   abort: acl: user "astro" not allowed on branch "default" (changeset "ef1ea85a6374")
   no rollback information available
   2:fb35475503ef
   
   $ do_push george
@@ -1800,17 +1800,17 @@  Branch acl allow other
   acl: path access granted: "ef1ea85a6374"
   acl: branch access granted: "f9cafe1212c8" on branch "default"
   acl: path access granted: "f9cafe1212c8"
   acl: branch access granted: "911600dab2ae" on branch "default"
   acl: path access granted: "911600dab2ae"
   acl: branch access granted: "e8fc755d4d82" on branch "foobar"
   acl: path access granted: "e8fc755d4d82"
   updating the branch cache
-  bundle2-input-part: total payload size 2101
+  bundle2-input-part: total payload size 2139
   bundle2-input-part: "pushkey" (params: 4 mandatory) supported
   pushing key for "phases:911600dab2ae7a9baff75958b84fe606851ce955"
   bundle2-input-part: "pushkey" (params: 4 mandatory) supported
   pushing key for "phases:e8fc755d4d8217ee5b0c2bb41558c40d43b92c01"
   bundle2-input-bundle: 4 parts total
   bundle2-output-bundle: "HG20", 3 parts total
   bundle2-output-part: "reply:changegroup" (advisory) (params: 0 advisory) empty payload
   bundle2-output-part: "reply:pushkey" (params: 0 advisory) empty payload
@@ -1893,17 +1893,17 @@  push foobar into the remote
   acl: path access granted: "ef1ea85a6374"
   acl: branch access granted: "f9cafe1212c8" on branch "default"
   acl: path access granted: "f9cafe1212c8"
   acl: branch access granted: "911600dab2ae" on branch "default"
   acl: path access granted: "911600dab2ae"
   acl: branch access granted: "e8fc755d4d82" on branch "foobar"
   acl: path access granted: "e8fc755d4d82"
   updating the branch cache
-  bundle2-input-part: total payload size 2101
+  bundle2-input-part: total payload size 2139
   bundle2-input-part: "pushkey" (params: 4 mandatory) supported
   pushing key for "phases:911600dab2ae7a9baff75958b84fe606851ce955"
   bundle2-input-part: "pushkey" (params: 4 mandatory) supported
   pushing key for "phases:e8fc755d4d8217ee5b0c2bb41558c40d43b92c01"
   bundle2-input-bundle: 4 parts total
   bundle2-output-bundle: "HG20", 3 parts total
   bundle2-output-part: "reply:changegroup" (advisory) (params: 0 advisory) empty payload
   bundle2-output-part: "reply:pushkey" (params: 0 advisory) empty payload
@@ -1977,17 +1977,17 @@  Branch acl conflicting deny
   added 4 changesets with 4 changes to 4 files (+1 heads)
   calling hook pretxnchangegroup.acl: hgext.acl.hook
   acl: checking access for user "george"
   acl: acl.allow.branches not enabled
   acl: acl.deny.branches enabled, 1 entries for user george
   acl: acl.allow not enabled
   acl: acl.deny not enabled
   error: pretxnchangegroup.acl hook failed: acl: user "george" denied on branch "default" (changeset "ef1ea85a6374")
-  bundle2-input-part: total payload size 2101
+  bundle2-input-part: total payload size 2139
   bundle2-input-bundle: 4 parts total
   transaction abort!
   rollback completed
   abort: acl: user "george" denied on branch "default" (changeset "ef1ea85a6374")
   no rollback information available
   2:fb35475503ef
   
 User 'astro' must not be denied
@@ -2054,17 +2054,17 @@  User 'astro' must not be denied
   acl: path access granted: "ef1ea85a6374"
   acl: branch access granted: "f9cafe1212c8" on branch "default"
   acl: path access granted: "f9cafe1212c8"
   acl: branch access granted: "911600dab2ae" on branch "default"
   acl: path access granted: "911600dab2ae"
   acl: branch access granted: "e8fc755d4d82" on branch "foobar"
   acl: path access granted: "e8fc755d4d82"
   updating the branch cache
-  bundle2-input-part: total payload size 2101
+  bundle2-input-part: total payload size 2139
   bundle2-input-part: "pushkey" (params: 4 mandatory) supported
   pushing key for "phases:911600dab2ae7a9baff75958b84fe606851ce955"
   bundle2-input-part: "pushkey" (params: 4 mandatory) supported
   pushing key for "phases:e8fc755d4d8217ee5b0c2bb41558c40d43b92c01"
   bundle2-input-bundle: 4 parts total
   bundle2-output-bundle: "HG20", 3 parts total
   bundle2-output-part: "reply:changegroup" (advisory) (params: 0 advisory) empty payload
   bundle2-output-part: "reply:pushkey" (params: 0 advisory) empty payload
@@ -2132,17 +2132,17 @@  Non-astro users must be denied
   added 4 changesets with 4 changes to 4 files (+1 heads)
   calling hook pretxnchangegroup.acl: hgext.acl.hook
   acl: checking access for user "george"
   acl: acl.allow.branches not enabled
   acl: acl.deny.branches enabled, 1 entries for user george
   acl: acl.allow not enabled
   acl: acl.deny not enabled
   error: pretxnchangegroup.acl hook failed: acl: user "george" denied on branch "default" (changeset "ef1ea85a6374")
-  bundle2-input-part: total payload size 2101
+  bundle2-input-part: total payload size 2139
   bundle2-input-bundle: 4 parts total
   transaction abort!
   rollback completed
   abort: acl: user "george" denied on branch "default" (changeset "ef1ea85a6374")
   no rollback information available
   2:fb35475503ef
   
 
diff --git a/tests/test-excessive-merge.t b/tests/test-excessive-merge.t
--- a/tests/test-excessive-merge.t
+++ b/tests/test-excessive-merge.t
@@ -64,17 +64,17 @@ 
   summary:     test
   
   $ hg debugindex --changelog
      rev    offset  length  ..... linkrev nodeid       p1           p2 (re)
        0         0      60  .....       0 5e0375449e74 000000000000 000000000000 (re)
        1        60      62  .....       1 96155394af80 5e0375449e74 000000000000 (re)
        2       122      62  .....       2 92cc4c306b19 5e0375449e74 000000000000 (re)
        3       184      69  .....       3 e16a66a37edd 92cc4c306b19 96155394af80 (re)
-       4       253      29  .....       4 2ee31f665a86 96155394af80 92cc4c306b19 (re)
+       4       253      69  .....       4 2ee31f665a86 96155394af80 92cc4c306b19 (re)
 
 revision 1
   $ hg manifest --debug 1
   79d7492df40aa0fa093ec4209be78043c181f094 644   a
   2ed2a3912a0b24502043eae84ee4b279c18b90dd 644   b
 revision 2
   $ hg manifest --debug 2
   2ed2a3912a0b24502043eae84ee4b279c18b90dd 644   a
diff --git a/tests/test-ssh-bundle1.t b/tests/test-ssh-bundle1.t
--- a/tests/test-ssh-bundle1.t
+++ b/tests/test-ssh-bundle1.t
@@ -55,18 +55,18 @@  non-existent absolute path
   remote: abort: repository /$TESTTMP/nonexistent not found!
   abort: no suitable response from remote hg!
   [255]
 
 clone remote via stream
 
   $ hg clone -e "python \"$TESTDIR/dummyssh\"" --uncompressed ssh://user@dummy/remote local-stream
   streaming all changes
-  4 files to transfer, 615 bytes of data
-  transferred 615 bytes in * seconds (*) (glob)
+  4 files to transfer, 602 bytes of data
+  transferred 602 bytes in * seconds (*) (glob)
   searching for changes
   no changes found
   updating to branch default
   2 files updated, 0 files merged, 0 files removed, 0 files unresolved
   $ cd local-stream
   $ hg verify
   checking changesets
   checking manifests
@@ -77,18 +77,18 @@  clone remote via stream
   default                        0:1160648e36ce
   $ cd ..
 
 clone bookmarks via stream
 
   $ hg -R local-stream book mybook
   $ hg clone -e "python \"$TESTDIR/dummyssh\"" --uncompressed ssh://user@dummy/local-stream stream2
   streaming all changes
-  4 files to transfer, 615 bytes of data
-  transferred 615 bytes in * seconds (*) (glob)
+  4 files to transfer, 602 bytes of data
+  transferred 602 bytes in * seconds (*) (glob)
   searching for changes
   no changes found
   updating to branch default
   2 files updated, 0 files merged, 0 files removed, 0 files unresolved
   $ cd stream2
   $ hg book
      mybook                    0:1160648e36ce
   $ cd ..
diff --git a/tests/test-ssh.t b/tests/test-ssh.t
--- a/tests/test-ssh.t
+++ b/tests/test-ssh.t
@@ -49,18 +49,18 @@  non-existent absolute path
   remote: abort: repository $TESTTMP/nonexistent not found!
   abort: no suitable response from remote hg!
   [255]
 
 clone remote via stream
 
   $ hg clone -e "python \"$TESTDIR/dummyssh\"" --uncompressed ssh://user@dummy/remote local-stream
   streaming all changes
-  4 files to transfer, 615 bytes of data
-  transferred 615 bytes in * seconds (*) (glob)
+  4 files to transfer, 602 bytes of data
+  transferred 602 bytes in * seconds (*) (glob)
   searching for changes
   no changes found
   updating to branch default
   2 files updated, 0 files merged, 0 files removed, 0 files unresolved
   $ cd local-stream
   $ hg verify
   checking changesets
   checking manifests
@@ -71,18 +71,18 @@  clone remote via stream
   default                        0:1160648e36ce
   $ cd ..
 
 clone bookmarks via stream
 
   $ hg -R local-stream book mybook
   $ hg clone -e "python \"$TESTDIR/dummyssh\"" --uncompressed ssh://user@dummy/local-stream stream2
   streaming all changes
-  4 files to transfer, 615 bytes of data
-  transferred 615 bytes in * seconds (*) (glob)
+  4 files to transfer, 602 bytes of data
+  transferred 602 bytes in * seconds (*) (glob)
   searching for changes
   no changes found
   updating to branch default
   2 files updated, 0 files merged, 0 files removed, 0 files unresolved
   $ cd stream2
   $ hg book
      mybook                    0:1160648e36ce
   $ cd ..