From: Dennis Zhou <dennis@kernel.org>
To: David Sterba <dsterba@suse.com>, Chris Mason <clm@fb.com>,
Josef Bacik <josef@toxicpanda.com>,
Omar Sandoval <osandov@osandov.com>
Cc: kernel-team@fb.com, linux-btrfs@vger.kernel.org,
Dennis Zhou <dennis@kernel.org>
Subject: [PATCH 18/19] btrfs: increase the metadata allowance for the free_space_cache
Date: Mon, 7 Oct 2019 16:17:49 -0400 [thread overview]
Message-ID: <4b171367793ccdcd722e787e5ae0f4f547ed5c43.1570479299.git.dennis@kernel.org> (raw)
In-Reply-To: <cover.1570479299.git.dennis@kernel.org>
In-Reply-To: <cover.1570479299.git.dennis@kernel.org>
Currently, there is no way for the free space cache to recover from
being serviced by purely bitmaps because the extent threshold is set to
0 in recalculate_thresholds() when we surpass the metadata allowance.
This adds a recovery mechanism by keeping large extents out of the
bitmaps and increases the metadata upper bound to 64KB. The recovery
mechanism bypasses this upper bound, thus making it a soft upper bound.
But, with the bypass being 1MB or greater, it shouldn't add unbounded
overhead.
Signed-off-by: Dennis Zhou <dennis@kernel.org>
---
fs/btrfs/free-space-cache.c | 26 +++++++++++---------------
1 file changed, 11 insertions(+), 15 deletions(-)
diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c
index 480119016c0d..a0941d281a63 100644
--- a/fs/btrfs/free-space-cache.c
+++ b/fs/btrfs/free-space-cache.c
@@ -24,7 +24,8 @@
#include "discard.h"
#define BITS_PER_BITMAP (PAGE_SIZE * 8UL)
-#define MAX_CACHE_BYTES_PER_GIG SZ_32K
+#define MAX_CACHE_BYTES_PER_GIG SZ_64K
+#define FORCE_EXTENT_THRESHOLD SZ_1M
struct btrfs_trim_range {
u64 start;
@@ -1686,26 +1687,17 @@ static void recalculate_thresholds(struct btrfs_free_space_ctl *ctl)
ASSERT(ctl->total_bitmaps <= max_bitmaps);
/*
- * The goal is to keep the total amount of memory used per 1gb of space
- * at or below 32k, so we need to adjust how much memory we allow to be
- * used by extent based free space tracking
+ * We are trying to keep the total amount of memory used per 1gb of
+ * space to be MAX_CACHE_BYTES_PER_GIG. However, with a reclamation
+ * mechanism of pulling extents >= FORCE_EXTENT_THRESHOLD out of
+ * bitmaps, we may end up using more memory than this.
*/
if (size < SZ_1G)
max_bytes = MAX_CACHE_BYTES_PER_GIG;
else
max_bytes = MAX_CACHE_BYTES_PER_GIG * div_u64(size, SZ_1G);
- /*
- * we want to account for 1 more bitmap than what we have so we can make
- * sure we don't go over our overall goal of MAX_CACHE_BYTES_PER_GIG as
- * we add more bitmaps.
- */
- bitmap_bytes = (ctl->total_bitmaps + 1) * ctl->unit;
-
- if (bitmap_bytes >= max_bytes) {
- ctl->extents_thresh = 0;
- return;
- }
+ bitmap_bytes = ctl->total_bitmaps * ctl->unit;
/*
* we want the extent entry threshold to always be at most 1/2 the max
@@ -2086,6 +2078,10 @@ static bool use_bitmap(struct btrfs_free_space_ctl *ctl,
forced = true;
#endif
+ /* this is a way to reclaim large regions from the bitmaps */
+ if (!forced && info->bytes >= FORCE_EXTENT_THRESHOLD)
+ return false;
+
/*
* If we are below the extents threshold then we can add this as an
* extent, and don't have to deal with the bitmap
--
2.17.1
next prev parent reply other threads:[~2019-10-07 20:18 UTC|newest]
Thread overview: 71+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-07 20:17 [RFC PATCH 00/19] btrfs: async discard support Dennis Zhou
2019-10-07 20:17 ` [PATCH 01/19] bitmap: genericize percpu bitmap region iterators Dennis Zhou
2019-10-07 20:26 ` Josef Bacik
2019-10-07 22:24 ` Dennis Zhou
2019-10-15 12:11 ` David Sterba
2019-10-15 18:35 ` Dennis Zhou
2019-10-07 20:17 ` [PATCH 02/19] btrfs: rename DISCARD opt to DISCARD_SYNC Dennis Zhou
2019-10-07 20:27 ` Josef Bacik
2019-10-08 11:12 ` Johannes Thumshirn
2019-10-11 9:19 ` Nikolay Borisov
2019-10-07 20:17 ` [PATCH 03/19] btrfs: keep track of which extents have been discarded Dennis Zhou
2019-10-07 20:37 ` Josef Bacik
2019-10-07 22:38 ` Dennis Zhou
2019-10-10 13:40 ` Josef Bacik
2019-10-11 16:15 ` Dennis Zhou
2019-10-08 12:46 ` Nikolay Borisov
2019-10-11 16:08 ` Dennis Zhou
2019-10-15 12:17 ` David Sterba
2019-10-15 19:58 ` Dennis Zhou
2019-10-07 20:17 ` [PATCH 04/19] btrfs: keep track of cleanliness of the bitmap Dennis Zhou
2019-10-10 14:16 ` Josef Bacik
2019-10-11 16:17 ` Dennis Zhou
2019-10-15 12:23 ` David Sterba
2019-10-07 20:17 ` [PATCH 05/19] btrfs: add the beginning of async discard, discard workqueue Dennis Zhou
2019-10-10 14:38 ` Josef Bacik
2019-10-15 12:49 ` David Sterba
2019-10-15 19:57 ` Dennis Zhou
2019-10-07 20:17 ` [PATCH 06/19] btrfs: handle empty block_group removal Dennis Zhou
2019-10-10 15:00 ` Josef Bacik
2019-10-11 16:52 ` Dennis Zhou
2019-10-07 20:17 ` [PATCH 07/19] btrfs: discard one region at a time in async discard Dennis Zhou
2019-10-10 15:22 ` Josef Bacik
2019-10-14 19:42 ` Dennis Zhou
2019-10-07 20:17 ` [PATCH 08/19] btrfs: track discardable extents for asnyc discard Dennis Zhou
2019-10-10 15:36 ` Josef Bacik
2019-10-14 19:50 ` Dennis Zhou
2019-10-15 13:12 ` David Sterba
2019-10-15 18:41 ` Dennis Zhou
2019-10-07 20:17 ` [PATCH 09/19] btrfs: keep track of discardable_bytes Dennis Zhou
2019-10-10 15:38 ` Josef Bacik
2019-10-07 20:17 ` [PATCH 10/19] btrfs: calculate discard delay based on number of extents Dennis Zhou
2019-10-10 15:41 ` Josef Bacik
2019-10-11 18:07 ` Dennis Zhou
2019-10-07 20:17 ` [PATCH 11/19] btrfs: add bps discard rate limit Dennis Zhou
2019-10-10 15:47 ` Josef Bacik
2019-10-14 19:56 ` Dennis Zhou
2019-10-07 20:17 ` [PATCH 12/19] btrfs: limit max discard size for async discard Dennis Zhou
2019-10-10 16:16 ` Josef Bacik
2019-10-14 19:57 ` Dennis Zhou
2019-10-07 20:17 ` [PATCH 13/19] btrfs: have multiple discard lists Dennis Zhou
2019-10-10 16:51 ` Josef Bacik
2019-10-14 20:04 ` Dennis Zhou
2019-10-07 20:17 ` [PATCH 14/19] btrfs: only keep track of data extents for async discard Dennis Zhou
2019-10-10 16:53 ` Josef Bacik
2019-10-07 20:17 ` [PATCH 15/19] btrfs: load block_groups into discard_list on mount Dennis Zhou
2019-10-10 17:11 ` Josef Bacik
2019-10-14 20:17 ` Dennis Zhou
2019-10-14 23:38 ` David Sterba
2019-10-15 15:42 ` Dennis Zhou
2019-10-07 20:17 ` [PATCH 16/19] btrfs: keep track of discard reuse stats Dennis Zhou
2019-10-10 17:13 ` Josef Bacik
2019-10-07 20:17 ` [PATCH 17/19] btrfs: add async discard header Dennis Zhou
2019-10-10 17:13 ` Josef Bacik
2019-10-07 20:17 ` Dennis Zhou [this message]
2019-10-10 17:16 ` [PATCH 18/19] btrfs: increase the metadata allowance for the free_space_cache Josef Bacik
2019-10-07 20:17 ` [PATCH 19/19] btrfs: make smaller extents more likely to go into bitmaps Dennis Zhou
2019-10-10 17:17 ` Josef Bacik
2019-10-11 7:49 ` [RFC PATCH 00/19] btrfs: async discard support Nikolay Borisov
2019-10-14 21:05 ` Dennis Zhou
2019-10-15 12:08 ` David Sterba
2019-10-15 15:41 ` Dennis Zhou
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