On 25.07.2017 23:51, jeffm@xxxxxxxx wrote:
> From: Jeff Mahoney <jeffm@xxxxxxxx>
>
> We have the infrastructure to cache extent buffers but we don't actually
> do the caching. As soon as the last reference is dropped, the buffer
> is dropped. This patch keeps the extent buffers around until the max
> cache size is reached (defaults to 25% of memory) and then it drops
> the last 10% of the LRU to free up cache space for reallocation. The
> cache size is configurable (for use by e.g. lowmem) when the cache is
> initialized.
>
> Signed-off-by: Jeff Mahoney <jeffm@xxxxxxxx>
> ---
> extent_io.c | 74 ++++++++++++++++++++++++++++++++++++++++++++++++++-----------
> extent_io.h | 4 ++++
> utils.c | 12 ++++++++++
> utils.h | 3 +++
> 4 files changed, 80 insertions(+), 13 deletions(-)
>
> diff --git a/extent_io.c b/extent_io.c
> index 915c6ed..937ff90 100644
> --- a/extent_io.c
> +++ b/extent_io.c
> @@ -27,6 +27,7 @@
> #include "list.h"
> #include "ctree.h"
> #include "volumes.h"
> +#include "utils.h"
> #include "internal.h"
>
> void extent_io_tree_init(struct extent_io_tree *tree)
> @@ -35,6 +36,14 @@ void extent_io_tree_init(struct extent_io_tree *tree)
> cache_tree_init(&tree->cache);
> INIT_LIST_HEAD(&tree->lru);
> tree->cache_size = 0;
> + tree->max_cache_size = (u64)(total_memory() * 1024) / 4;
> +}
> +
> +void extent_io_tree_init_cache_max(struct extent_io_tree *tree,
> + u64 max_cache_size)
> +{
> + extent_io_tree_init(tree);
> + tree->max_cache_size = max_cache_size;
> }
>
> static struct extent_state *alloc_extent_state(void)
> @@ -67,16 +76,20 @@ static void free_extent_state_func(struct cache_extent *cache)
> btrfs_free_extent_state(es);
> }
>
> +static void free_extent_buffer_final(struct extent_buffer *eb);
> void extent_io_tree_cleanup(struct extent_io_tree *tree)
> {
> struct extent_buffer *eb;
>
> while(!list_empty(&tree->lru)) {
> eb = list_entry(tree->lru.next, struct extent_buffer, lru);
> - fprintf(stderr, "extent buffer leak: "
> - "start %llu len %u\n",
> - (unsigned long long)eb->start, eb->len);
> - free_extent_buffer(eb);
> + if (eb->refs) {
> + fprintf(stderr, "extent buffer leak: "
> + "start %llu len %u\n",
> + (unsigned long long)eb->start, eb->len);
> + free_extent_buffer_nocache(eb);
> + } else
> + free_extent_buffer_final(eb);
> }
>
> cache_tree_free_extents(&tree->state, free_extent_state_func);
> @@ -567,7 +580,21 @@ struct extent_buffer *btrfs_clone_extent_buffer(struct extent_buffer *src)
> return new;
> }
>
> -void free_extent_buffer(struct extent_buffer *eb)
> +static void free_extent_buffer_final(struct extent_buffer *eb)
> +{
> + struct extent_io_tree *tree = eb->tree;
> +
> + BUG_ON(eb->refs);
> + BUG_ON(tree->cache_size < eb->len);
> + list_del_init(&eb->lru);
> + if (!(eb->flags & EXTENT_BUFFER_DUMMY)) {
> + remove_cache_extent(&tree->cache, &eb->cache_node);
> + tree->cache_size -= eb->len;
> + }
> + free(eb);
> +}
> +
> +static void free_extent_buffer_internal(struct extent_buffer *eb, int free_now)
nit: free_ow -> boolean
> {
> if (!eb || IS_ERR(eb))
> return;
> @@ -575,19 +602,23 @@ void free_extent_buffer(struct extent_buffer *eb)
> eb->refs--;
> BUG_ON(eb->refs < 0);
> if (eb->refs == 0) {
> - struct extent_io_tree *tree = eb->tree;
> BUG_ON(eb->flags & EXTENT_DIRTY);
> - list_del_init(&eb->lru);
> list_del_init(&eb->recow);
> - if (!(eb->flags & EXTENT_BUFFER_DUMMY)) {
> - BUG_ON(tree->cache_size < eb->len);
> - remove_cache_extent(&tree->cache, &eb->cache_node);
> - tree->cache_size -= eb->len;
> - }
> - free(eb);
> + if (eb->flags & EXTENT_BUFFER_DUMMY || free_now)
> + free_extent_buffer_final(eb);
> }
> }
>
> +void free_extent_buffer(struct extent_buffer *eb)
> +{
> + free_extent_buffer_internal(eb, 0);
> +}
> +
> +void free_extent_buffer_nocache(struct extent_buffer *eb)
> +{
> + free_extent_buffer_internal(eb, 1);
> +}
> +
> struct extent_buffer *find_extent_buffer(struct extent_io_tree *tree,
> u64 bytenr, u32 blocksize)
> {
> @@ -619,6 +650,21 @@ struct extent_buffer *find_first_extent_buffer(struct extent_io_tree *tree,
> return eb;
> }
>
> +static void
> +trim_extent_buffer_cache(struct extent_io_tree *tree)
> +{
> + struct extent_buffer *eb, *tmp;
> + u64 count = 0;
count seems to be a leftover from something, so you could remove it
> + list_for_each_entry_safe(eb, tmp, &tree->lru, lru) {
> + if (eb->refs == 0) {
> + free_extent_buffer_final(eb);
> + count++;
> + }
> + if (tree->cache_size <= ((tree->max_cache_size * 9) / 10))
> + break;
> + }
> +}
> +
> struct extent_buffer *alloc_extent_buffer(struct extent_io_tree *tree,
> u64 bytenr, u32 blocksize)
> {
> @@ -649,6 +695,8 @@ struct extent_buffer *alloc_extent_buffer(struct extent_io_tree *tree,
> }
> list_add_tail(&eb->lru, &tree->lru);
> tree->cache_size += blocksize;
> + if (tree->cache_size >= tree->max_cache_size)
> + trim_extent_buffer_cache(tree);
> }
> return eb;
> }
> diff --git a/extent_io.h b/extent_io.h
> index e617489..17a4a82 100644
> --- a/extent_io.h
> +++ b/extent_io.h
> @@ -75,6 +75,7 @@ struct extent_io_tree {
> struct cache_tree cache;
> struct list_head lru;
> u64 cache_size;
> + u64 max_cache_size;
> };
>
> struct extent_state {
> @@ -106,6 +107,8 @@ static inline void extent_buffer_get(struct extent_buffer *eb)
> }
>
> void extent_io_tree_init(struct extent_io_tree *tree);
> +void extent_io_tree_init_cache_max(struct extent_io_tree *tree,
> + u64 max_cache_size);
> void extent_io_tree_cleanup(struct extent_io_tree *tree);
> int set_extent_bits(struct extent_io_tree *tree, u64 start, u64 end, int bits);
> int clear_extent_bits(struct extent_io_tree *tree, u64 start, u64 end, int bits);
> @@ -146,6 +149,7 @@ struct extent_buffer *alloc_extent_buffer(struct extent_io_tree *tree,
> u64 bytenr, u32 blocksize);
> struct extent_buffer *btrfs_clone_extent_buffer(struct extent_buffer *src);
> void free_extent_buffer(struct extent_buffer *eb);
> +void free_extent_buffer_nocache(struct extent_buffer *eb);
> int read_extent_from_disk(struct extent_buffer *eb,
> unsigned long offset, unsigned long len);
> int write_extent_to_disk(struct extent_buffer *eb);
> diff --git a/utils.c b/utils.c
> index d2489e7..c565e08 100644
> --- a/utils.c
> +++ b/utils.c
> @@ -24,6 +24,7 @@
> #include <sys/mount.h>
> #include <sys/types.h>
> #include <sys/stat.h>
> +#include <sys/sysinfo.h>
> #include <uuid/uuid.h>
> #include <fcntl.h>
> #include <unistd.h>
> @@ -2521,3 +2522,14 @@ u8 rand_u8(void)
> void btrfs_config_init(void)
> {
> }
> +
> +unsigned long total_memory(void)
perhaps rename to total_memory_bytes and return the memory size in
bytes. Returning them in kilobytes seems rather arbitrary. That way
you'd save the constant *1024 to turn the kbs in bytes in the callers
(currently only in extent_io_tree_init())
> +{
> + struct sysinfo si;
> +
> + if (sysinfo(&si) < 0) {
> + error("can't determine memory size");
> + return -1UL;
> + }
> + return (si.totalram >> 10) * si.mem_unit; /* kilobytes */
> +}
> diff --git a/utils.h b/utils.h
> index 24d0a20..6be0d6f 100644
> --- a/utils.h
> +++ b/utils.h
> @@ -148,6 +148,9 @@ unsigned int get_unit_mode_from_arg(int *argc, char *argv[], int df_mode);
> int string_is_numerical(const char *str);
> int prefixcmp(const char *str, const char *prefix);
>
> +/* Returns total size of main memory in KiB units. -1ULL if error. */
> +unsigned long total_memory(void);
> +
> /*
> * Global program state, configurable by command line and available to
> * functions without extra context passing.
>
--
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