The patch is extracted from Google patches.

The patch adds information about where fsync call was initiated from. The information is available in SHOW INNODB STATUS output. There is BACKGROUND THREAD section (this is new section) with fsync callers

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BACKGROUND THREAD
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fsync callers: 609 buffer pool, 89 other, 86 checkpoint, 105 log aio, 126 log sync, 0 archive

And also patch extends LOG section

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LOG
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390 log i/o's done, 0.00 log i/o's/second, **126 syncs, 5384 checkpoints**
log sync callers: 29459 buffer pool, background 122 sync and 124 async, 110 internal, checkpoint 5384 sync and 0 async, 0 archive, commit 0 sync and 2 async
log sync syncers: 7 buffer pool, background 118 sync and 0 async, 0 internal, checkpoint 1 sync and 0 async, 0 archive, commit 0 sync and 0 async

It shows how many syncs and checkpoints for log were executed and sources of log sync callers. There difference between “caller” and “syncer” is that for “syncer” was used fsync call.