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xfs: invert the realtime summary cache

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In commit 355e353213 ("xfs: cache minimum realtime summary level"), I
added a cache of the minimum level of the realtime summary that has any
free extents. However, it turns out that the _maximum_ level is more
useful for upcoming optimizations, and basically equivalent for the
existing usage. So, let's change the meaning of the cache to be the
maximum level + 1, or 0 if there are no free extents.

For example, if the cache contains:

{0, 4}

then there are no free extents starting in realtime bitmap block 0, and
there are no free extents larger than or equal to 2^4 blocks starting in
realtime bitmap block 1. The cache is a loose upper bound, so there may
or may not be free extents smaller than 2^4 blocks in realtime bitmap
block 1.

Signed-off-by: Omar Sandoval <osandov@fb.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
This commit is contained in:
Omar Sandoval
2023-10-16 10:41:55 -07:00
committed by Darrick J. Wong
parent e2cf427c91
commit e23aaf450d
3 changed files with 25 additions and 18 deletions
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31
fs/xfs/xfs_rtalloc.c
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@@ -54,14 +54,19 @@ xfs_rtany_summary(
int log; /* loop counter, log2 of ext. size */
xfs_suminfo_t sum; /* summary data */
/* There are no extents at levels < m_rsum_cache[bbno]. */
if (mp->m_rsum_cache && low < mp->m_rsum_cache[bbno])
low = mp->m_rsum_cache[bbno];
/* There are no extents at levels >= m_rsum_cache[bbno]. */
if (mp->m_rsum_cache) {
high = min(high, mp->m_rsum_cache[bbno] - 1);
if (low > high) {
*stat = 0;
return 0;
}
}
/*
* Loop over logs of extent sizes.
*/
for (log = low; log <= high; log++) {
for (log = high; log >= low; log--) {
/*
* Get one summary datum.
*/
@@ -82,9 +87,9 @@ xfs_rtany_summary(
*/
*stat = 0;
out:
/* There were no extents at levels < log. */
if (mp->m_rsum_cache && log > mp->m_rsum_cache[bbno])
mp->m_rsum_cache[bbno] = log;
/* There were no extents at levels > log. */
if (mp->m_rsum_cache && log + 1 < mp->m_rsum_cache[bbno])
mp->m_rsum_cache[bbno] = log + 1;
return 0;
}
@@ -887,12 +892,14 @@ xfs_alloc_rsum_cache(
xfs_extlen_t rbmblocks) /* number of rt bitmap blocks */
{
/*
* The rsum cache is initialized to all zeroes, which is trivially a
* lower bound on the minimum level with any free extents. We can
* continue without the cache if it couldn't be allocated.
* The rsum cache is initialized to the maximum value, which is
* trivially an upper bound on the maximum level with any free extents.
* We can continue without the cache if it couldn't be allocated.
*/
mp->m_rsum_cache = kvzalloc(rbmblocks, GFP_KERNEL);
if (!mp->m_rsum_cache)
mp->m_rsum_cache = kvmalloc(rbmblocks, GFP_KERNEL);
if (mp->m_rsum_cache)
memset(mp->m_rsum_cache, -1, rbmblocks);
else
xfs_warn(mp, "could not allocate realtime summary cache");
}