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| author | Jan Kara <jack@suse.cz> | 2021-09-02 14:53:04 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2021-09-03 09:58:10 -0700 |
| commit | 633a2abb9e1cd5c95f3b600f4b2c12cce22ae4a0 (patch) | |
| tree | a7ff91638eb5b03dca868ec1be8a6bdff4b9b5c8 /fs/fs-writeback.c | |
| parent | eb2169cee36fc492407a2d483c286b977a46288a (diff) | |
| download | lwn-633a2abb9e1cd5c95f3b600f4b2c12cce22ae4a0.tar.gz lwn-633a2abb9e1cd5c95f3b600f4b2c12cce22ae4a0.zip | |
writeback: track number of inodes under writeback
Patch series "writeback: Fix bandwidth estimates", v4.
Fix estimate of writeback throughput when device is not fully busy doing
writeback. Michael Stapelberg has reported that such workload (e.g.
generated by linking) tends to push estimated throughput down to 0 and as
a result writeback on the device is practically stalled.
The first three patches fix the reported issue, the remaining two patches
are unrelated cleanups of problems I've noticed when reading the code.
This patch (of 4):
Track number of inodes under writeback for each bdi_writeback structure.
We will use this to decide whether wb does any IO and so we can estimate
its writeback throughput. In principle we could use number of pages under
writeback (WB_WRITEBACK counter) for this however normal percpu counter
reads are too inaccurate for our purposes and summing the counter is too
expensive.
Link: https://lkml.kernel.org/r/20210713104519.16394-1-jack@suse.cz
Link: https://lkml.kernel.org/r/20210713104716.22868-1-jack@suse.cz
Signed-off-by: Jan Kara <jack@suse.cz>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Cc: Michael Stapelberg <stapelberg+linux@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'fs/fs-writeback.c')
| -rw-r--r-- | fs/fs-writeback.c | 5 |
1 files changed, 5 insertions, 0 deletions
diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c index 4c3370548982..7439ecd44ac9 100644 --- a/fs/fs-writeback.c +++ b/fs/fs-writeback.c @@ -406,6 +406,11 @@ static bool inode_do_switch_wbs(struct inode *inode, inc_wb_stat(new_wb, WB_WRITEBACK); } + if (mapping_tagged(mapping, PAGECACHE_TAG_WRITEBACK)) { + atomic_dec(&old_wb->writeback_inodes); + atomic_inc(&new_wb->writeback_inodes); + } + wb_get(new_wb); /* |