[Qt] Reduce a significant cs_main lock freeze #10231

jonasschnelli · 2017-04-19T16:05:29Z

I can't remember why we added this in the first place: but in current master, we request a cs_main lock (not a try lock) every block tip update in order to get the best headers height / time.
This results in significant freezes in the GUI during IBD/catch-up.

This PR adds two atomic caches for the best headers height and time.

If we do a 0.14.1rc3, we should consider adding this.

TheBlueMatt · 2017-04-19T16:34:26Z

Can the GUI instead cache the current best tip? This may help with @ryanofsky's process split as well.

jonasschnelli · 2017-04-19T16:34:55Z

@TheBlueMatt: Yes. @theuni recommended this on IRC and I'm currently changing it.

jonasschnelli · 2017-04-19T16:52:41Z

Moved the cache from the core validation logic to the GUI.

gmaxwell · 2017-04-19T17:28:42Z

src/qt/clientmodel.cpp

-    if (!pindexBestHeader)
-        return 0;
-    return pindexBestHeader->nHeight;
+    if (cachedBestHeaderHeight == 0) {


Where is this initialized? -- these don't have static duration AFAICT.

Also is zero really the best value to use? -- it's in range, so it'll keep relocking again while there is no data there.

gmaxwell · 2017-04-19T17:29:26Z

What does the GUI use the header time/height for as opposed to the tip?

jonasschnelli · 2017-04-19T18:55:08Z

Thanks @gmaxwell. Added the missing initialisation and switched to -1 as indicator wether the cache is set or not.

What does the GUI use the header time/height for as opposed to the tip?

The only use case is to calculate the remaining blocks to download/validate (modal sync progress overlay).

luke-jr

utACK

luke-jr · 2017-04-19T19:07:36Z

src/qt/clientmodel.cpp

@@ -72,20 +74,28 @@ int ClientModel::getNumBlocks() const
    return chainActive.Height();
 }

-int ClientModel::getHeaderTipHeight() const
+int ClientModel::getHeaderTipHeight()


Maybe this should remain const, and declare the caches mutable?

luke-jr · 2017-04-19T19:09:24Z

src/qt/clientmodel.cpp

+        // otherwise we need to wait for a tip update
+        LOCK(cs_main);
+        if (pindexBestHeader) {
+            cachedBestHeaderHeight = pindexBestHeader->nHeight;


Would it make sense to populate both caches at once perhaps?

TheBlueMatt · 2017-04-19T20:20:01Z

utACK

gmaxwell

utACK

jonasschnelli · 2017-04-20T07:55:53Z

Followed @luke-jr's advice and re-set the method to const and declared the cache atomic's mutable.
Also, both caches are now getting set regardless of the called method. Yes, you could argue to have an explicit function to set the cache to avoid code duplication. But for two lines it's not worth in my opinion.

@gmaxwell, @TheBlueMatt: thanks for a re-ack. :)

laanwj · 2017-04-20T11:41:00Z

Less blocking of the gui on cs_main is always a good thing, thanks!
utACK 4082fb0

4082fb0 Add missing <atomic> header in clientmodel.h (Jonas Schnelli) 928d4a9 Set both time/height header caches at the same time (Jonas Schnelli) 610a917 Declare headers height/time cache mutable, re-set the methods const (Jonas Schnelli) cf92bce Update the remaining blocks left in modaloverlay at init. (Jonas Schnelli) 7148f5e Reduce cs_main locks during modal overlay by adding an atomic cache (Jonas Schnelli) Tree-SHA512: a92ca22f90b8b2a5e8eb94fdce531ef44542e21a8dbbb0693f7723d7018592cb68de687a2a0aac91d31cbf019793f8e922550656d2b130ed3d854d60630341db

Github-Pull: bitcoin#10231 Rebased-From: 7148f5e

Github-Pull: bitcoin#10231 Rebased-From: cf92bce

Github-Pull: bitcoin#10231 Rebased-From: 610a917

Github-Pull: bitcoin#10231 Rebased-From: 928d4a9

Github-Pull: bitcoin#10231 Rebased-From: 4082fb0

4082fb0 Add missing <atomic> header in clientmodel.h (Jonas Schnelli) 928d4a9 Set both time/height header caches at the same time (Jonas Schnelli) 610a917 Declare headers height/time cache mutable, re-set the methods const (Jonas Schnelli) cf92bce Update the remaining blocks left in modaloverlay at init. (Jonas Schnelli) 7148f5e Reduce cs_main locks during modal overlay by adding an atomic cache (Jonas Schnelli) Tree-SHA512: a92ca22f90b8b2a5e8eb94fdce531ef44542e21a8dbbb0693f7723d7018592cb68de687a2a0aac91d31cbf019793f8e922550656d2b130ed3d854d60630341db

…1704) 4082fb0 Add missing <atomic> header in clientmodel.h (Jonas Schnelli) 928d4a9 Set both time/height header caches at the same time (Jonas Schnelli) 610a917 Declare headers height/time cache mutable, re-set the methods const (Jonas Schnelli) cf92bce Update the remaining blocks left in modaloverlay at init. (Jonas Schnelli) 7148f5e Reduce cs_main locks during modal overlay by adding an atomic cache (Jonas Schnelli) Tree-SHA512: a92ca22f90b8b2a5e8eb94fdce531ef44542e21a8dbbb0693f7723d7018592cb68de687a2a0aac91d31cbf019793f8e922550656d2b130ed3d854d60630341db

jonasschnelli added GUI Needs backport labels Apr 19, 2017

jonasschnelli force-pushed the 2017/04/qt_freeze branch from 737adc1 to 745a27f Compare April 19, 2017 16:51

gmaxwell reviewed Apr 19, 2017

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jonasschnelli force-pushed the 2017/04/qt_freeze branch from 745a27f to 42e30f4 Compare April 19, 2017 18:12

Reduce cs_main locks during modal overlay by adding an atomic cache

7148f5e

jonasschnelli force-pushed the 2017/04/qt_freeze branch from 42e30f4 to 7148f5e Compare April 19, 2017 18:54

Update the remaining blocks left in modaloverlay at init.

cf92bce

luke-jr approved these changes Apr 19, 2017

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gmaxwell approved these changes Apr 20, 2017

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jonasschnelli added 2 commits April 20, 2017 09:51

Declare headers height/time cache mutable, re-set the methods const

610a917

Set both time/height header caches at the same time

928d4a9

Add missing <atomic> header in clientmodel.h

4082fb0

laanwj merged commit 4082fb0 into bitcoin:master Apr 20, 2017

luke-jr pushed a commit to bitcoinknots/bitcoin that referenced this pull request Apr 21, 2017

Reduce cs_main locks during modal overlay by adding an atomic cache

213ee4f

Github-Pull: bitcoin#10231 Rebased-From: 7148f5e

luke-jr pushed a commit to bitcoinknots/bitcoin that referenced this pull request Apr 21, 2017

Update the remaining blocks left in modaloverlay at init.

1e435ed

Github-Pull: bitcoin#10231 Rebased-From: cf92bce

luke-jr pushed a commit to bitcoinknots/bitcoin that referenced this pull request Apr 21, 2017

Declare headers height/time cache mutable, re-set the methods const

b19ecc4

Github-Pull: bitcoin#10231 Rebased-From: 610a917

luke-jr pushed a commit to bitcoinknots/bitcoin that referenced this pull request Apr 21, 2017

Set both time/height header caches at the same time

4c9ec97

Github-Pull: bitcoin#10231 Rebased-From: 928d4a9

luke-jr pushed a commit to bitcoinknots/bitcoin that referenced this pull request Apr 21, 2017

Add missing <atomic> header in clientmodel.h

e8350f9

Github-Pull: bitcoin#10231 Rebased-From: 4082fb0

maflcko added this to the 0.14.2 milestone Apr 23, 2017

jonasschnelli mentioned this pull request May 31, 2017

wallet 0.14.1 not responding #10349

Closed

jonasschnelli mentioned this pull request May 31, 2017

0.14 Backports #10484

Merged

laanwj removed the Needs backport label May 31, 2017

laanwj mentioned this pull request Jun 27, 2017

Windows Gui becomes non responsive after "Done loading" #10646

Closed

codablock mentioned this pull request Oct 31, 2017

Backport #10231: [Qt] Reduce a significant cs_main lock freeze dashpay/dash#1704

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bitcoin locked as resolved and limited conversation to collaborators Sep 8, 2021

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[Qt] Reduce a significant cs_main lock freeze #10231

[Qt] Reduce a significant cs_main lock freeze #10231

jonasschnelli commented Apr 19, 2017 •

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[Qt] Reduce a significant cs_main lock freeze #10231

[Qt] Reduce a significant cs_main lock freeze #10231

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