During IBD, when doing pruning, prune 10% extra to avoid pruning again soon after #11658

pull luke-jr wants to merge 1 commits into bitcoin:master from luke-jr:ibd_prune_extra changing 1 files +9 −0

luke-jr commented at 9:08 AM on November 11, 2017: member

Pruning forces a chainstate flush, which can defeat the dbcache and harm performance significantly.

Alternative to #11359

During IBD, when doing pruning, prune 10% extra to avoid pruning again soon after

Pruning forces a chainstate flush, which can defeat the dbcache and harm performance significantly.

ac51a26bdc

fanquake added the label Validation on Nov 11, 2017

in src/validation.cpp:3399 in ac51a26bdc

3390 | @@ -3391,6 +3391,15 @@ void FindFilesToPrune(std::set<int>& setFilesToPrune, uint64_t nPruneAfterHeight
3391 |      int count=0;
3392 |  
3393 |      if (nCurrentUsage + nBuffer >= nPruneTarget) {
3394 | +        // On a prune event, the chainstate DB is flushed.
3395 | +        // To avoid excessive prune events negating the benefit of high dbcache
3396 | +        // values, we should not prune too rapidly.
3397 | +        // So when pruning in IBD, increase the buffer a bit to avoid a re-prune too soon.
3398 | +        if (IsInitialBlockDownload()) {
3399 | +            // Since this is only relevant during IBD, we use a fixed 10%

promag commented at 4:14 PM on November 15, 2017:

BTW, why 10%, in IBD could be even more no?

Sjors commented at 11:29 AM on December 7, 2017: member

Some IRC discussion.
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Sjors commented at 11:06 AM on May 28, 2018: member

tACK ac51a26 (although I rebased it on master).

This performs better than master in my tests so far: #12404 (comment) @promag wrote:

BTW, why 10%, in IBD could be even more no?

I tried this in #12404 and there seems to be negative side effects that I can't explain. I'd say this PR is a safer choice for now. @luke-jr you may want to borrow the release note I added to my PR, though that can be done later.
Sjors commented at 12:06 PM on June 14, 2018: member

I'm currently racing two Orange Pi's with 2 GB memory. This PR means cache rarely grows beyond 300 MB, but it's still a bit faster than master; after 5 days it's at 2018-01-27 vs. master is still at 2017-11-25.
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sipa commented at 3:05 AM on July 6, 2018: member

utACK ac51a26bdc69dc35e1f4f89b62c3134047e93bc1. This should be a safe first improvement. We can later make the overshoot value configurable or smarter, but this should already be a lot better.
MarcoFalke added the label Needs release notes on Jul 7, 2018
MarcoFalke removed the label Needs release notes on Jul 7, 2018
promag commented at 10:04 PM on July 7, 2018: member

utACK ac51a26. Improvement looks good.
ajtowns commented at 6:50 AM on July 12, 2018: member

utACK ac51a26bdc69dc35e1f4f89b62c3134047e93bc1
achow101 commented at 10:56 PM on July 13, 2018: member

utACK ac51a26bdc69dc35e1f4f89b62c3134047e93bc1
sipa merged this on Jul 14, 2018
sipa closed this on Jul 14, 2018
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fanquake removed this from the "Blockers" column in a project

ajtowns commented at 7:40 AM on July 16, 2018: member

Post-merge tested ACK.

I ran this on some memory-constrained Linodes (dbcache=1000, prune=5000, and both connect= to a single nearby fully synced node; 2GB memory, 50GB disk), and saw a reasonably consistent 15% performance increase compared to not having this patch.
martinpgaunt commented at 7:48 AM on July 16, 2018: none

How use this ?
fanquake deleted a comment on Jul 16, 2018
Sjors commented at 8:30 AM on July 16, 2018: member

@martinpgaunt it just works, if you download Bitcoin Core 0.17 when it comes out in a couple of weeks (or a bit later).
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#11359 Add a pruning 'high water mark' to reduce the frequency of pruning events