linux-kernel - Re: [PATCH v2] ceph: Mark the file cache as unreclaimable

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Date:	Tue, 26 Jul 2016 10:24:23 +0800
From:	"Yan, Zheng" <zyan@...hat.com>
To:	Nikolay Borisov <n.borisov.lkml@...il.com>
Cc:	Sage Weil <sage@...hat.com>, Ilya Dryomov <idryomov@...il.com>,
	Ceph Development <ceph-devel@...r.kernel.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] ceph: Mark the file cache as unreclaimable


> On Jul 26, 2016, at 01:12, Nikolay Borisov <n.borisov.lkml@...il.com> wrote:
> 
> Ceph creates multiple caches with the SLAB_RECLAIMABLE flag set, so
> that it can satisfy its internal needs. Inspecting the code shows that
> most of the caches are indeed reclaimable since they are directly
> related to the generic inode/dentry shrinkers. However, one of the
> cache used to satisfy struct file is not reclaimable since its
> entries are freed only when the last reference to the file is
> dropped. If a heavily loaded node opens a lot of files it can
> introduce non-trivial discrepancies between memory shown as reclaimable
> and what is actually reclaimed when drop_caches is used.
> 
> Fix this by removing the reclaimable flag for the file's cache.
> 
> Signed-off-by: Nikolay Borisov <n.borisov.lkml@...il.com>
> ---
> 
> Fixed checkpatch warning + missing SOB line
> 
> fs/ceph/super.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/ceph/super.c b/fs/ceph/super.c
> index 91e02481ce06..8697cac6add0 100644
> --- a/fs/ceph/super.c
> +++ b/fs/ceph/super.c
> @@ -672,8 +672,8 @@ static int __init init_caches(void)
> 	if (ceph_dentry_cachep == NULL)
> 		goto bad_dentry;
> 
> -	ceph_file_cachep = KMEM_CACHE(ceph_file_info,
> -				      SLAB_RECLAIM_ACCOUNT|SLAB_MEM_SPREAD);
> +	ceph_file_cachep = KMEM_CACHE(ceph_file_info, SLAB_MEM_SPREAD);
> +
> 	if (ceph_file_cachep == NULL)
> 		goto bad_file;
> 

Applied, thanks

Yan, Zheng

> -- 
> 2.7.4
>