Messages in this thread Patch in this message | | | Date | Fri, 4 Jul 2014 10:38:17 +0200 | From | Sebastien Buisson <> | Subject | [PATCH] Allow increasing the buffer-head per-CPU LRU size |
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Allow increasing the buffer-head per-CPU LRU size to allow efficient filesystem operations that access many blocks for each transaction. For example, creating a file in a large ext4 directory with quota enabled will accesses multiple buffer heads and will overflow the LRU at the default 8-block LRU size:
* parent directory inode table block (ctime, nlinks for subdirs) * new inode bitmap * inode table block * 2 quota blocks * directory leaf block (not reused, but pollutes one cache entry) * 2 levels htree blocks (only one is reused, other pollutes cache) * 2 levels indirect/index blocks (only one is reused)
The buffer-head per-CPU LRU size can be changed at config time, and its default value is raised to 16.
Signed-off-by: Liang Zhen <liang.zhen@intel.com> Signed-off-by: Andreas Dilger <andreas.dilger@intel.com> --- fs/Kconfig | 9 +++++++++ fs/buffer.c | 3 +-- 2 files changed, 10 insertions(+), 2 deletions(-)
diff --git a/fs/Kconfig b/fs/Kconfig index c229f82..afea808 100644 --- a/fs/Kconfig +++ b/fs/Kconfig @@ -268,4 +268,13 @@ endif # NETWORK_FILESYSTEMS source "fs/nls/Kconfig" source "fs/dlm/Kconfig"
+config BH_LRU_SIZE + int "buffer head per-CPU LRU size" + range 8 64 + default "16" + help + This sets the per-CPU LRU size for buffer heads in memory. + More complex filesystems may be modiyfing multiple blocks + within a single transaction, so keeping the buffer heads in + CPU-local cache speeds up modifations significantly. endmenu diff --git a/fs/buffer.c b/fs/buffer.c index 6024877..b83fa63 100644 --- a/fs/buffer.c +++ b/fs/buffer.c @@ -1255,8 +1255,7 @@ static struct buffer_head *__bread_slow(struct buffer_head *bh) * The LRUs themselves only need locking against invalidate_bh_lrus. We use * a local interrupt disable for that. */ - -#define BH_LRU_SIZE 8 +#define BH_LRU_SIZE CONFIG_BH_LRU_SIZE
struct bh_lru { struct buffer_head *bhs[BH_LRU_SIZE]; -- 1.7.1
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