reactor: change shares for default IO class from 1 to 200 #1706
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The number of shares is supposed to be set in the 1-1000 range, and user-defined IO classes have shares on the order of hundreds in practice. Therefore, 1 share is not a sane default, because the default class can very easily be starved by accident. We have seen in practice for example in scylladb/scylladb#13753.
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There's no 'backport' label here, but I assume our intention is to pick this up for stable versions. |
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@avikivity I'm not sure if we want this change in seastar master (this could be a backwards-incompatible change for some users), or only in Scylla's stable forks of Seastar. What's your judgement? |
Yes. |
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Is it a regression or shares==1 has always been there?
…On Mon, Jun 19, 2023 at 12:47 PM Michał Chojnowski ***@***.***> wrote:
The number of shares is supposed to be set in the 1-1000 range, and
user-defined IO classes have shares on the order of hundreds in practice.
Therefore, 1 share is not a sane default, because the default class can
very easily be starved by accident.
We have seen in practice for example in scylladb/scylladb#13753
<scylladb/scylladb#13753>.
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#1706
Commit Summary
- 638919d
<638919d>
reactor: change shares for default IO class from 1 to 200
File Changes
(1 file <https://github.com/scylladb/seastar/pull/1706/files>)
- *M* src/core/reactor.cc
<https://github.com/scylladb/seastar/pull/1706/files#diff-5e5dfd46a396d71e0d68f183d6eb0f3bb5aad37be914323b8e4fea134dafec0c>
(2)
Patch Links:
- https://github.com/scylladb/seastar/pull/1706.patch
- https://github.com/scylladb/seastar/pull/1706.diff
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Since f259b31 (so: since forever). |
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Ping. |
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@avikivity @xemul Bump. Do we want this change in seastar master (this could be a backwards-incompatible change for some users), or only in |
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This code is obsolete in API level 7. So let's go for minimum disruption and only apply the change to ScyllaDB. |
Then please create branch-5.3 in scylla-seastar, so we can backport seastar fixes to 5.3. |
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Done. |
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Transferred to scylladb/scylla-seastar#3. |
The number of shares is supposed to be set in the 1-1000 range, and user-defined IO classes have shares on the order of hundreds in practice.
Therefore, 1 share is not a sane default, because the default class can very easily be starved by accident.
We have seen in practice for example in scylladb/scylladb#13753.