On Tue, 30 Nov 2010 19:25:36 +0530
Suresh Jayaraman <sjayaraman@xxxxxxx> wrote:
> On 11/30/2010 07:20 PM, Suresh Jayaraman wrote:
> > Currently, the attribute cache timeout for CIFS is hardcoded to 1 second. This
> > means that the client might have to issue a QPATHINFO/QFILEINFO call every 1
> > second to verify if something has changes, which seems too expensive. On the
> > other hand, if the timeout is hardcoded to a higher value, workloads that
> > expect strict cache coherency might see unexpected results.
> >
> > Making attribute cache timeout as a tunable will allow us to make a tradeoff
> > between performance and cache metadata correctness depending on the
> > application/workload needs.
> >
> > Add 'actimeo' tunable that can be used to tune the attribute cache timeout.
> > The default timeout is set to 1 second. Also, display actimeo option value in
> > /proc/mounts.
> >
> > It appears to me that 'actimeo' and the proposed (but not yet merged)
> > 'strictcache' option cannot coexist, so care must be taken that we reset the
> > other option if one of them is set.
> >
> > Changes since last post:
> > - guard against wraparound issues with a max timeout value (25 days)
>
> Forgot to mention: The rationale behind choosing 25 days instead of
> using a jiffie equivalent is that the jiffie value calculated might
> change based on HZ value. Suppose, in a setup where there are clients
> with different HZ values, the same actimeo setting might lead to
> different timeout.
>
I can understand the rationale, but my thinking there is "tough luck".
If someone uses a value that large. In practice people will mostly move
this out to the order of a few minutes, or will set it to 0.
The main thing that we want to avoid is someone setting this to a value
that's going to screw it up. If that limit is different on different
machines, then so be it.
> > - handle actimeo=0 condition correctly
> >
> > Cc: Jeff Layton <jlayton@xxxxxxxxxx>
> > Signed-off-by: Suresh Jayaraman <sjayaraman@xxxxxxx>
> > ---
> > fs/cifs/README | 9 +++++++++
> > fs/cifs/cifs_fs_sb.h | 1 +
> > fs/cifs/cifsfs.c | 2 ++
> > fs/cifs/cifsglob.h | 12 ++++++++++++
> > fs/cifs/connect.c | 18 ++++++++++++++++++
> > fs/cifs/inode.c | 7 ++++---
> > 6 files changed, 46 insertions(+), 3 deletions(-)
> >
> > diff --git a/fs/cifs/README b/fs/cifs/README
> > index ee68d10..46af99a 100644
> > --- a/fs/cifs/README
> > +++ b/fs/cifs/README
> > @@ -337,6 +337,15 @@ A partial list of the supported mount options follows:
> > wsize default write size (default 57344)
> > maximum wsize currently allowed by CIFS is 57344 (fourteen
> > 4096 byte pages)
> > + actimeo=n attribute cache timeout in seconds (default 1 second).
> > + After this timeout, the cifs client requests fresh attribute
> > + information from the server. This option allows to tune the
> > + attribute cache timeout to suit the workload needs. Shorter
> > + timeouts mean better the cache coherency, but increased number
> > + of calls to the server. Longer timeouts mean reduced number
> > + of calls to the server at the expense of less stricter cache
> > + coherency checks (i.e. incorrect attribute cache for a short
> > + period of time).
> > rw mount the network share read-write (note that the
> > server may still consider the share read-only)
> > ro mount network share read-only
> > diff --git a/fs/cifs/cifs_fs_sb.h b/fs/cifs/cifs_fs_sb.h
> > index e9a393c..7852cd6 100644
> > --- a/fs/cifs/cifs_fs_sb.h
> > +++ b/fs/cifs/cifs_fs_sb.h
> > @@ -48,6 +48,7 @@ struct cifs_sb_info {
> > struct nls_table *local_nls;
> > unsigned int rsize;
> > unsigned int wsize;
> > + unsigned long actimeo; /* attribute cache timeout (jiffies) */
> > atomic_t active;
> > uid_t mnt_uid;
> > gid_t mnt_gid;
> > diff --git a/fs/cifs/cifsfs.c b/fs/cifs/cifsfs.c
> > index 76c8a90..56a4b75 100644
> > --- a/fs/cifs/cifsfs.c
> > +++ b/fs/cifs/cifsfs.c
> > @@ -463,6 +463,8 @@ cifs_show_options(struct seq_file *s, struct vfsmount *m)
> >
> > seq_printf(s, ",rsize=%d", cifs_sb->rsize);
> > seq_printf(s, ",wsize=%d", cifs_sb->wsize);
> > + /* convert actimeo and display it in seconds */
> > + seq_printf(s, ",actimeo=%lu", cifs_sb->actimeo / HZ);
> >
> > return 0;
> > }
> > diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
> > index b577bf0..1c9363c 100644
> > --- a/fs/cifs/cifsglob.h
> > +++ b/fs/cifs/cifsglob.h
> > @@ -45,6 +45,18 @@
> > #define CIFS_MIN_RCV_POOL 4
> >
> > /*
> > + * default attribute cache timeout (jiffies)
> > + */
> > +#define CIFS_DEF_ACTIMEO (1 * HZ)
> > +
> > +#define SECS_PER_DAY (24 * 60 * 60)
> > +/*
> > + * max attribute cache timeout (jiffies)
> > + * set to 25 days which should be long enough
> > + */
> > +#define CIFS_MAX_ACTIMEO (SECS_PER_DAY * 25 * HZ)
> > +
> > +/*
> > * MAX_REQ is the maximum number of requests that WE will send
> > * on one socket concurrently. It also matches the most common
> > * value of max multiplex returned by servers. We may
> > diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
> > index 32fa4d9..ee7cb11 100644
> > --- a/fs/cifs/connect.c
> > +++ b/fs/cifs/connect.c
> > @@ -105,6 +105,7 @@ struct smb_vol {
> > unsigned int wsize;
> > bool sockopt_tcp_nodelay:1;
> > unsigned short int port;
> > + unsigned long actimeo; /* attribute cache timeout (jiffies) */
> > char *prepath;
> > struct sockaddr_storage srcaddr; /* allow binding to a local IP */
> > struct nls_table *local_nls;
> > @@ -1214,6 +1215,15 @@ cifs_parse_mount_options(char *options, const char *devname,
> > printk(KERN_WARNING "CIFS: server net"
> > "biosname longer than 15 truncated.\n");
> > }
> > + } else if (strnicmp(data, "actimeo", 7) == 0) {
> > + if (value) {
> > + if (*value)
> > + vol->actimeo =
> > + simple_strtoul(value,
> > + &value, 0) * HZ;
> > + else
> > + vol->actimeo = 0;
> > + }
> > } else if (strnicmp(data, "credentials", 4) == 0) {
> > /* ignore */
> > } else if (strnicmp(data, "version", 3) == 0) {
> > @@ -2571,6 +2581,14 @@ static void setup_cifs_sb(struct smb_vol *pvolume_info,
> > cFYI(1, "file mode: 0x%x dir mode: 0x%x",
> > cifs_sb->mnt_file_mode, cifs_sb->mnt_dir_mode);
> >
> > + if (pvolume_info->actimeo >= 0) {
> > + if (pvolume_info->actimeo < CIFS_MAX_ACTIMEO)
> > + cifs_sb->actimeo = pvolume_info->actimeo;
> > + else
> > + cifs_sb->actimeo = CIFS_MAX_ACTIMEO;
> > + } else /* default */
> > + cifs_sb->actimeo = CIFS_DEF_ACTIMEO;
> > +
> > if (pvolume_info->noperm)
> > cifs_sb->mnt_cifs_flags |= CIFS_MOUNT_NO_PERM;
> > if (pvolume_info->setuids)
> > diff --git a/fs/cifs/inode.c b/fs/cifs/inode.c
> > index 28cb6e7..6040679 100644
> > --- a/fs/cifs/inode.c
> > +++ b/fs/cifs/inode.c
> > @@ -1653,6 +1653,7 @@ static bool
> > cifs_inode_needs_reval(struct inode *inode)
> > {
> > struct cifsInodeInfo *cifs_i = CIFS_I(inode);
> > + struct cifs_sb_info *cifs_sb = CIFS_SB(inode->i_sb);
> >
> > if (cifs_i->clientCanCacheRead)
> > return false;
> > @@ -1663,12 +1664,12 @@ cifs_inode_needs_reval(struct inode *inode)
> > if (cifs_i->time == 0)
> > return true;
> >
> > - /* FIXME: the actimeo should be tunable */
> > - if (time_after_eq(jiffies, cifs_i->time + HZ))
> > + if (!time_in_range_open(jiffies, cifs_i->time,
> > + cifs_i->time + cifs_sb->actimeo))
> > return true;
> >
> > /* hardlinked files w/ noserverino get "special" treatment */
> > - if (!(CIFS_SB(inode->i_sb)->mnt_cifs_flags & CIFS_MOUNT_SERVER_INUM) &&
> > + if (!(cifs_sb->mnt_cifs_flags & CIFS_MOUNT_SERVER_INUM) &&
> > S_ISREG(inode->i_mode) && inode->i_nlink != 1)
> > return true;
> >
> > --
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>
>
--
Jeff Layton <jlayton@xxxxxxxxxx>
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