Kent Overstreet 1d18b5cabc bcachefs: __bch2_read(): call trans_begin() on every loop iter
perusal of /sys/kernel/debug/bcachefs/*/btree_transaction_stats shows
that the read path has been acculumalating unneeded paths on the reflink
btree, which we don't want.

The solution is to call bch2_trans_begin(), which drops paths not used
on previous loop iteration.

bch2_readahead:
  Max mem used: 0
  Transaction duration:
    count:      194235
                           since mount        recent
    duration of events
      min:                      150 ns
      max:                        9 ms
      total:                    838 ms
      mean:                       4 us          6 us
      stddev:                    34 us          7 us
    time between events
      min:                       10 ns
      max:                       15 h
      mean:                       2 s          12 s
      stddev:                     2 s           3 ms
  Maximum allocated btree paths (193):
    path: idx  2 ref 0:0 P   btree=extents l=0 pos 270943112:392:U32_MAX locks 0
    path: idx  3 ref 1:0   S btree=extents l=0 pos 270943112:24578:U32_MAX locks 1
    path: idx  4 ref 0:0 P   btree=reflink l=0 pos 0:24773509:0 locks 0
    path: idx  5 ref 0:0 P S btree=reflink l=0 pos 0:24773631:0 locks 1
    path: idx  6 ref 0:0 P S btree=reflink l=0 pos 0:24773759:0 locks 1
    path: idx  7 ref 0:0 P S btree=reflink l=0 pos 0:24773887:0 locks 1
    path: idx  8 ref 0:0 P S btree=reflink l=0 pos 0:24774015:0 locks 1
    path: idx  9 ref 0:0 P S btree=reflink l=0 pos 0:24774143:0 locks 1
    path: idx 10 ref 0:0 P S btree=reflink l=0 pos 0:24774271:0 locks 1
<many more reflink paths>

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
2024-07-14 19:00:16 -04:00
2022-09-28 09:02:20 +02:00
2024-07-14 15:43:32 -07:00
2024-03-18 03:36:32 -06:00

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.
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