Verilog · Beginners · Cut our verilog-newbie build from 4 minutes to 40 seconds with these 5 changes

118
VEr/verilog-newbie·posted by nikic·3 hours agoReview

Cut our verilog-newbie build from 4 minutes to 40 seconds with these 5 changes

It took me two weeks of on-and-off digging and plenty of wrong turns. Writing the process down as it happened so the next person spends less time.

We also fixed monitoring along the way: replaced average-based alerts with percentiles and split them per endpoint. False alerts dropped by about seventy percent and the on-call rotation visibly cheered up.

The first thing was to collapse the variables. We were changing config and upgrading the version at the same time, and afterwards nobody could say which change caused what. We rolled back to moving one variable at a time, re-ran three times, and only then did the curve settle. Tedious, but not skippable.

Ddev.toExternal link · opens in a new tab
59 comments

59 comments

M
WwinterOP·2 days ago

Agreeing with the above. One addition: with this option enabled the GC count in your metrics doubles, so adjust the alert threshold at the same time or it will keep firing.

442
Nnikic·2 days agoedited

I see point 3 differently. The trade-off depends on your read/write ratio: read-heavy with little writing means caching actually widens the inconsistency window.

489
Zzhu_zong·just now

Worth learning from this debugging approach. We went straight at the logs and took a much longer route.

396
Sswoole_leeOP·2 days ago

This matches what we see in production. We only hit it past 3k QPS; the earlier load tests showed nothing — the test traffic was too clean, with no long-tail requests.

324
Kkite·1 hour ago

Agreeing with the above. One addition: with this option enabled the GC count in your metrics doubles, so adjust the alert threshold at the same time or it will keep firing.

175
Kkernel_panic·yesterday

I just read the verilog-newbie source — the author actually explains the reasoning in a comment, roughly "so that it degrades into predictable behaviour in extreme cases".

150
Bbob_chen·2 days ago

Worth learning from this debugging approach. We went straight at the logs and took a much longer route.

147
Zzhou_yi·1 hour agoedited

Saved. I am reworking this area this week — this saves a lot of wrong turns.

365
Ttang_hao·2 days agoedited

Worth learning from this debugging approach. We went straight at the logs and took a much longer route.

142
Bbob_chen·1 hour ago

Saved. I am reworking this area this week — this saves a lot of wrong turns.

106
Sswoole_lee·12 minutes agoedited

There is actually a simpler fix that needs no architecture change: move this check up to the gateway and the problem disappears. The cost is one extra lookup at the gateway.

95
Rrase·28 minutes ago

A question: what changes in a container with a 512Mi memory limit? That is how we run it in production.

1
Rrase·1 hour ago

Has anyone run a controlled experiment? I did, reducing it to a single variable, and the difference was 4% — within noise. So I suspect the main cause is something else.

23
Oops_wang·2 days ago

Sharing our numbers, 8 cores 16GB, same scenario:

| Concurrency | P50 | P99 |
|---|---|---|
| 200 | 12ms | 88ms |
| 500 | 31ms | 340ms |

P99 clearly collapses at 500 concurrency, which lines up with your knee point.

6
Lli_ming·28 minutes ago

Has anyone run a controlled experiment? I did, reducing it to a single variable, and the difference was 4% — within noise. So I suspect the main cause is something else.

2
Kkite·yesterday

Agreeing with the above. One addition: with this option enabled the GC count in your metrics doubles, so adjust the alert threshold at the same time or it will keep firing.

17
Bbob_chen·2 days ago

A question: what changes in a container with a 512Mi memory limit? That is how we run it in production.

3
Llinlin·2 days ago

We have run this in production for two years without hitting it. That said, we never reached this scale, so our experience is not really evidence here.

87
Cchen_dev·2 days ago

I just read the verilog-newbie source — the author actually explains the reasoning in a comment, roughly "so that it degrades into predictable behaviour in extreme cases".

253
Mmike_xu·2 days agoedited

Has anyone run a controlled experiment? I did, reducing it to a single variable, and the difference was 4% — within noise. So I suspect the main cause is something else.

2
Cchen_dev·2 days ago

There is actually a simpler fix that needs no architecture change: move this check up to the gateway and the problem disappears. The cost is one extra lookup at the gateway.

450
Sslow_queryOP·yesterday

I see point 3 differently. The trade-off depends on your read/write ratio: read-heavy with little writing means caching actually widens the inconsistency window.

21
Cchen_devOP·28 minutes ago

This matches what we see in production. We only hit it past 3k QPS; the earlier load tests showed nothing — the test traffic was too clean, with no long-tail requests.

1
Kkernel_panic·just now

One counter-example: below verilog-newbie 7.4 the semantics of that code are different, so do not copy it verbatim. We got burned in staging and rolled back once.

177
Cchen_dev·2 days ago

One counter-example: below verilog-newbie 7.4 the semantics of that code are different, so do not copy it verbatim. We got burned in staging and rolled back once.

53
Sswoole_lee·2 days ago

Can you give a minimal reproduction? I ran it locally for ten minutes and could not reproduce on macOS with the latest version.

50
Llinlin·28 minutes ago

Can you give a minimal reproduction? I ran it locally for ten minutes and could not reproduce on macOS with the latest version.

36
Cchen_dev·3 minutes ago

Saved. I am reworking this area this week — this saves a lot of wrong turns.

211
Wwinter·28 minutes ago

Thanks for sharing real numbers — far more useful than the articles that only cover concepts.

317
Bbob_chen·2 days agoedited

This is not a verilog-newbie problem, it is a usage problem. The docs say this API is not thread-safe and you must lock around it yourself.

123
Kkernel_panic·12 minutes ago

Thanks for sharing real numbers — far more useful than the articles that only cover concepts.

141
Bbob_chen·5 hours ago

This is not a verilog-newbie problem, it is a usage problem. The docs say this API is not thread-safe and you must lock around it yourself.

51
Ddev_zhou·2 days ago

Worth learning from this debugging approach. We went straight at the logs and took a much longer route.

146
Zzhu_zong·3 minutes ago

Sharing our numbers, 8 cores 16GB, same scenario:

| Concurrency | P50 | P99 |
|---|---|---|
| 200 | 12ms | 88ms |
| 500 | 31ms | 340ms |

P99 clearly collapses at 500 concurrency, which lines up with your knee point.

18
Mmike_xu·1 hour ago

Has anyone run a controlled experiment? I did, reducing it to a single variable, and the difference was 4% — within noise. So I suspect the main cause is something else.

1
Bbob_chen·2 days ago

Saved. I am reworking this area this week — this saves a lot of wrong turns.

1
Nnikic·2 days ago

I just read the verilog-newbie source — the author actually explains the reasoning in a comment, roughly "so that it degrades into predictable behaviour in extreme cases".

130
Hhuang_keOP·2 days ago

Thanks for sharing real numbers — far more useful than the articles that only cover concepts.

271
Ddev_zhou·28 minutes ago

I see point 3 differently. The trade-off depends on your read/write ratio: read-heavy with little writing means caching actually widens the inconsistency window.

71
Mmike_xu·2 hours ago

We have run this in production for two years without hitting it. That said, we never reached this scale, so our experience is not really evidence here.

8
Mmike_xu·2 days agoedited

There is actually a simpler fix that needs no architecture change: move this check up to the gateway and the problem disappears. The cost is one extra lookup at the gateway.

150
Mmike_xu·5 hours ago

A question: what changes in a container with a 512Mi memory limit? That is how we run it in production.

58
Sslow_query·3 minutes ago

Agreeing with the above. One addition: with this option enabled the GC count in your metrics doubles, so adjust the alert threshold at the same time or it will keep firing.

147
Kkernel_panicOP·2 days ago

A question: what changes in a container with a 512Mi memory limit? That is how we run it in production.

442
Cchen_dev·1 hour agoedited

We have run this in production for two years without hitting it. That said, we never reached this scale, so our experience is not really evidence here.

19
Sslow_query·28 minutes ago

I see point 3 differently. The trade-off depends on your read/write ratio: read-heavy with little writing means caching actually widens the inconsistency window.

42
Kkernel_panic·2 days ago

This matches what we see in production. We only hit it past 3k QPS; the earlier load tests showed nothing — the test traffic was too clean, with no long-tail requests.

182
Hhuang_ke·2 days ago

Can you give a minimal reproduction? I ran it locally for ten minutes and could not reproduce on macOS with the latest version.

1
Kkernel_panic·2 days ago

One counter-example: below verilog-newbie 7.4 the semantics of that code are different, so do not copy it verbatim. We got burned in staging and rolled back once.

97
Lli_ming·5 hours ago

This is not a verilog-newbie problem, it is a usage problem. The docs say this API is not thread-safe and you must lock around it yourself.

17
Rran_bo·2 days ago

Sharing our numbers, 8 cores 16GB, same scenario:

| Concurrency | P50 | P99 |
|---|---|---|
| 200 | 12ms | 88ms |
| 500 | 31ms | 340ms |

P99 clearly collapses at 500 concurrency, which lines up with your knee point.

13
Zzhou_yi·3 minutes ago

This is not a verilog-newbie problem, it is a usage problem. The docs say this API is not thread-safe and you must lock around it yourself.

11
Mmike_xu·just now

One counter-example: below verilog-newbie 7.4 the semantics of that code are different, so do not copy it verbatim. We got burned in staging and rolled back once.

11
Lli_ming·12 minutes ago

There is actually a simpler fix that needs no architecture change: move this check up to the gateway and the problem disappears. The cost is one extra lookup at the gateway.

9
Llinlin·2 days ago

I just read the verilog-newbie source — the author actually explains the reasoning in a comment, roughly "so that it degrades into predictable behaviour in extreme cases".

151
Nnikic·2 days ago

This matches what we see in production. We only hit it past 3k QPS; the earlier load tests showed nothing — the test traffic was too clean, with no long-tail requests.

6
Zzhu_zong·just nowedited

Thanks for sharing real numbers — far more useful than the articles that only cover concepts.

5
Zzhu_zong·2 days ago

Sharing our numbers, 8 cores 16GB, same scenario:

| Concurrency | P50 | P99 |
|---|---|---|
| 200 | 12ms | 88ms |
| 500 | 31ms | 340ms |

P99 clearly collapses at 500 concurrency, which lines up with your knee point.

4
Cchen_dev·2 days ago

Can you give a minimal reproduction? I ran it locally for ten minutes and could not reproduce on macOS with the latest version.

1

This is the post detail page /en/c/verilog-newbie/post/p8. Posts and comments are generated deterministically from a seeded PRNG, so the same post always renders the same content and the link can be shared, reloaded and indexed. In production this page reads MySQL for the post, Redis for hot-post caching, and fetches the whole comment tree in a single query on the path column.

See the database schema →