On 11/18/2010 12:09 AM, Jeff Layton wrote: > On Wed, 17 Nov 2010 23:53:34 +0530 > Suresh Jayaraman <[email protected]> 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. >> >> Cc: Jeff Layton <[email protected]> >> Signed-off-by: Suresh Jayaraman <[email protected]> >> --- >> fs/cifs/cifs_fs_sb.h | 1 + >> fs/cifs/cifsfs.c | 1 + >> fs/cifs/cifsglob.h | 5 +++++ >> fs/cifs/connect.c | 10 ++++++++++ >> fs/cifs/inode.c | 6 +++--- >> 5 files changed, 20 insertions(+), 3 deletions(-) >> >> diff --git a/fs/cifs/inode.c b/fs/cifs/inode.c >> index ff7d299..f30700d 100644 >> --- a/fs/cifs/inode.c >> +++ b/fs/cifs/inode.c >> @@ -1648,6 +1648,7 @@ 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; >> @@ -1658,12 +1659,11 @@ 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_after_eq(jiffies, cifs_i->time + (cifs_sb->actimeo * HZ))) > > Problem: > > Suppose (cifs_i->time + (cifs_sb->actimeo * HZ)) carries you > past two sign bit changes. At that point, it may look like > the resulting time is in the past, not the future.
Good catch. > You actually do need to impose a limit here. I suggest looking > very closely at time_before/time_after macros. It'll also be > easier to deal storing actimeo in terms of jiffies instead of > seconds. > Finally, this value needs to be displayed in /proc/mounts. > Did you mean displaying values in jiffies in /proc/mounts? Wouldn't it be confusing for users to see such a higher numbers (usually) when they had used a simple 2 digit number for e.g. during mount? -- Suresh Jayaraman -- To unsubscribe from this list: send the line "unsubscribe linux-cifs" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
