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Steven Whitehouse 04-10-2012 06:21 PM

GFS2: Instruct DLM to avoid queue convert slowdown
 
Hi,

On Tue, 2012-04-10 at 14:13 -0400, Bob Peterson wrote:
> Hi,
>
> Here is my revised patch based on Steve's suggestion to base the
> flag on the recent GLF_BLOCKING flag.
>
> We still need to keep this on hold until the prerequisite dlm patch
> is properly upstream.
>
> Regards,
>
> Bob Peterson
> Red Hat File Systems
>
> Signed-off-by: Bob Peterson <rpeterso@redhat.com>
> ---
> Author: Bob Peterson <rpeterso@redhat.com>
> Date: Tue Apr 10 14:08:11 2012 -0500
>
> GFS2: Instruct DLM to avoid queue convert slowdowns
>
> This patch instructs DLM to prevent an "in place" conversion, where the
> lock just stays on the granted queue, and instead forces the conversion to
> the back of the convert queue. This is done on upward conversions only.
>
> This is useful in cases where, for example, a lock is frequently needed in
> PR on one node, but another node needs it temporarily in EX to update it.
> This may happen, for example, when the rindex is being updated by gfs2_grow.
> The gfs2_grow needs to have the lock in EX, but the other nodes need to
> re-read it to retrieve the updates. The glock is already granted in PR on
> the non-growing nodes, so this prevents them from continually re-granting
> the lock in PR, and forces the EX from gfs2_grow to go through.
>
> diff --git a/fs/gfs2/lock_dlm.c b/fs/gfs2/lock_dlm.c
> index f8411bd..ed9c5ca 100644
> --- a/fs/gfs2/lock_dlm.c
> +++ b/fs/gfs2/lock_dlm.c
> @@ -200,11 +200,15 @@ static int make_mode(const unsigned int lmstate)
> return -1;
> }
>
> -static u32 make_flags(const u32 lkid, const unsigned int gfs_flags,
> +static u32 make_flags(struct gfs2_glock *gl, const unsigned int gfs_flags,
> const int req)
> {
> u32 lkf = DLM_LKF_VALBLK;
> + u32 lkid = gl->gl_lksb.sb_lkid;
> + int is_upconvert = 0;
>
> + if (test_bit(GLF_BLOCKING, &gl->gl_flags))
> + is_upconvert = 1;
Rather than create this is_upconvert variable here...

> if (gfs_flags & LM_FLAG_TRY)
> lkf |= DLM_LKF_NOQUEUE;
>
> @@ -227,8 +231,11 @@ static u32 make_flags(const u32 lkid, const unsigned int gfs_flags,
> BUG();
> }
>
> - if (lkid != 0)
> + if (lkid != 0) {
> lkf |= DLM_LKF_CONVERT;
> + if (is_upconvert)
why not just test the flag bit here?

Otherwise looks good,

Steve.

> + lkf |= DLM_LKF_QUECVT;
> + }
>
> return lkf;
> }
> @@ -250,7 +257,7 @@ static int gdlm_lock(struct gfs2_glock *gl, unsigned int req_state,
> char strname[GDLM_STRNAME_BYTES] = "";
>
> req = make_mode(req_state);
> - lkf = make_flags(gl->gl_lksb.sb_lkid, flags, req);
> + lkf = make_flags(gl, flags, req);
> gfs2_glstats_inc(gl, GFS2_LKS_DCOUNT);
> gfs2_sbstats_inc(gl, GFS2_LKS_DCOUNT);
> if (gl->gl_lksb.sb_lkid) {
>


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