>[оверквотинг удален]
>- at vfs_cache_pressure=100 there is no change in behaviour.
>- at vfs_cache_pressure > 100 we reclaim dentries and inodes harder.
>
>Как я понял (если не так поправьте) увеличение параметра способствует сокращению кешей
>(dentries and inodes).
>Про то, что оно указывается в процентах от ОЗУ нигде не встречал.
>
>Думаю если уменьшить тягу к увеличению кеша, то все уместиться в ОЗУ,
>и не будет так медлить при работе. Вот и интересуюсь как
>это сделать. Вот кстати те участки кода где задействовано vfs_cache_pressure:
../fs/inode.c
/*
* shrink_icache_memory() will attempt to reclaim some unused inodes. Here,
* "unused" means that no dentries are referring to the inodes: the files are
* not open and the dcache references to those inodes have already been
* reclaimed.
*
* This function is passed the number of inodes to scan, and it returns the
* total number of remaining possibly-reclaimable inodes.
*/
static int shrink_icache_memory(int nr, gfp_t gfp_mask)
{
if (nr) {
/*
* Nasty deadlock avoidance. We may hold various FS locks,
* and we don't want to recurse into the FS that called us
* in clear_inode() and friends..
*/
if (!(gfp_mask & __GFP_FS))
return -1;
prune_icache(nr);
}
return (inodes_stat.nr_unused / 100) * sysctl_vfs_cache_pressure;
}
../fs/dcache.c
/*
* Scan `nr' dentries and return the number which remain.
*
* We need to avoid reentering the filesystem if the caller is performing a
* GFP_NOFS allocation attempt. One example deadlock is:
*
* ext2_new_block->getblk->GFP->shrink_dcache_memory->prune_dcache->
* prune_one_dentry->dput->dentry_iput->iput->inode->i_sb->s_op->put_inode->
* ext2_discard_prealloc->ext2_free_blocks->lock_super->DEADLOCK.
*
* In this case we return -1 to tell the caller that we baled.
*/
static int shrink_dcache_memory(int nr, gfp_t gfp_mask)
{
if (nr) {
if (!(gfp_mask & __GFP_FS))
return -1;
prune_dcache(nr);
}
return (dentry_stat.nr_unused / 100) * sysctl_vfs_cache_pressure;
}
../fs/mbcache.c
/*
* mb_cache_shrink_fn() memory pressure callback
*
* This function is called by the kernel memory management when memory
* gets low.
*
* @nr_to_scan: Number of objects to scan
* @gfp_mask: (ignored)
*
* Returns the number of objects which are present in the cache.
*/
static int
mb_cache_shrink_fn(int nr_to_scan, gfp_t gfp_mask)
{
LIST_HEAD(free_list);
struct list_head *l, *ltmp;
int count = 0;
spin_lock(&mb_cache_spinlock);
list_for_each(l, &mb_cache_list) {
struct mb_cache *cache =
list_entry(l, struct mb_cache, c_cache_list);
mb_debug("cache %s (%d)", cache->c_name,
atomic_read(&cache->c_entry_count));
count += atomic_read(&cache->c_entry_count);
}
mb_debug("trying to free %d entries", nr_to_scan);
if (nr_to_scan == 0) {
spin_unlock(&mb_cache_spinlock);
goto out;
}
while (nr_to_scan-- && !list_empty(&mb_cache_lru_list)) {
struct mb_cache_entry *ce =
list_entry(mb_cache_lru_list.next,
struct mb_cache_entry, e_lru_list);
list_move_tail(&ce->e_lru_list, &free_list);
__mb_cache_entry_unhash(ce);
}
spin_unlock(&mb_cache_spinlock);
list_for_each_safe(l, ltmp, &free_list) {
__mb_cache_entry_forget(list_entry(l, struct mb_cache_entry,
e_lru_list), gfp_mask);
}
out:
return (count / 100) * sysctl_vfs_cache_pressure;
}
