diff options
| -rw-r--r-- | fs/gfs2/rgrp.c | 94 |
1 files changed, 90 insertions, 4 deletions
diff --git a/fs/gfs2/rgrp.c b/fs/gfs2/rgrp.c index 669b89b95ccc..bdf3e644baae 100644 --- a/fs/gfs2/rgrp.c +++ b/fs/gfs2/rgrp.c @@ -1681,6 +1681,88 @@ static void try_rgrp_unlink(struct gfs2_rgrpd *rgd, u64 *last_unlinked, u64 skip return; } +/** + * gfs2_rgrp_congested - Use stats to figure out whether an rgrp is congested + * @rgd: The rgrp in question + * @loops: An indication of how picky we can be (0=very, 1=less so) + * + * This function uses the recently added glock statistics in order to + * figure out whether a parciular resource group is suffering from + * contention from multiple nodes. This is done purely on the basis + * of timings, since this is the only data we have to work with and + * our aim here is to reject a resource group which is highly contended + * but (very important) not to do this too often in order to ensure that + * we do not land up introducing fragmentation by changing resource + * groups when not actually required. + * + * The calculation is fairly simple, we want to know whether the SRTTB + * (i.e. smoothed round trip time for blocking operations) to acquire + * the lock for this rgrp's glock is significantly greater than the + * time taken for resource groups on average. We introduce a margin in + * the form of the variable @var which is computed as the sum of the two + * respective variences, and multiplied by a factor depending on @loops + * and whether we have a lot of data to base the decision on. This is + * then tested against the square difference of the means in order to + * decide whether the result is statistically significant or not. + * + * Returns: A boolean verdict on the congestion status + */ + +static bool gfs2_rgrp_congested(const struct gfs2_rgrpd *rgd, int loops) +{ + const struct gfs2_glock *gl = rgd->rd_gl; + const struct gfs2_sbd *sdp = gl->gl_sbd; + struct gfs2_lkstats *st; + s64 r_dcount, l_dcount; + s64 r_srttb, l_srttb; + s64 srttb_diff; + s64 sqr_diff; + s64 var; + + preempt_disable(); + st = &this_cpu_ptr(sdp->sd_lkstats)->lkstats[LM_TYPE_RGRP]; + r_srttb = st->stats[GFS2_LKS_SRTTB]; + r_dcount = st->stats[GFS2_LKS_DCOUNT]; + var = st->stats[GFS2_LKS_SRTTVARB] + + gl->gl_stats.stats[GFS2_LKS_SRTTVARB]; + preempt_enable(); + + l_srttb = gl->gl_stats.stats[GFS2_LKS_SRTTB]; + l_dcount = gl->gl_stats.stats[GFS2_LKS_DCOUNT]; + + if ((l_dcount < 1) || (r_dcount < 1) || (r_srttb == 0)) + return false; + + srttb_diff = r_srttb - l_srttb; + sqr_diff = srttb_diff * srttb_diff; + + var *= 2; + if (l_dcount < 8 || r_dcount < 8) + var *= 2; + if (loops == 1) + var *= 2; + + return ((srttb_diff < 0) && (sqr_diff > var)); +} + +/** + * gfs2_rgrp_used_recently + * @rs: The block reservation with the rgrp to test + * @msecs: The time limit in milliseconds + * + * Returns: True if the rgrp glock has been used within the time limit + */ +static bool gfs2_rgrp_used_recently(const struct gfs2_blkreserv *rs, + u64 msecs) +{ + u64 tdiff; + + tdiff = ktime_to_ns(ktime_sub(ktime_get_real(), + rs->rs_rbm.rgd->rd_gl->gl_dstamp)); + + return tdiff > (msecs * 1000 * 1000); +} + static bool gfs2_select_rgrp(struct gfs2_rgrpd **pos, const struct gfs2_rgrpd *begin) { struct gfs2_rgrpd *rgd = *pos; @@ -1707,7 +1789,7 @@ int gfs2_inplace_reserve(struct gfs2_inode *ip, u32 requested) struct gfs2_sbd *sdp = GFS2_SB(&ip->i_inode); struct gfs2_rgrpd *begin = NULL; struct gfs2_blkreserv *rs = ip->i_res; - int error = 0, rg_locked, flags = LM_FLAG_TRY; + int error = 0, rg_locked, flags = 0; u64 last_unlinked = NO_BLOCK; int loops = 0; @@ -1731,13 +1813,18 @@ int gfs2_inplace_reserve(struct gfs2_inode *ip, u32 requested) if (!gfs2_glock_is_locked_by_me(rs->rs_rbm.rgd->rd_gl)) { rg_locked = 0; + if (!gfs2_rs_active(rs) && (loops < 2) && + gfs2_rgrp_used_recently(rs, 1000) && + gfs2_rgrp_congested(rs->rs_rbm.rgd, loops)) + goto next_rgrp; error = gfs2_glock_nq_init(rs->rs_rbm.rgd->rd_gl, LM_ST_EXCLUSIVE, flags, &rs->rs_rgd_gh); - if (error == GLR_TRYFAILED) - goto next_rgrp; if (unlikely(error)) return error; + if (!gfs2_rs_active(rs) && (loops < 2) && + gfs2_rgrp_congested(rs->rs_rbm.rgd, loops)) + goto skip_rgrp; if (sdp->sd_args.ar_rgrplvb) { error = update_rgrp_lvb(rs->rs_rbm.rgd); if (unlikely(error)) { @@ -1789,7 +1876,6 @@ next_rgrp: * then this checks for some less likely conditions before * trying again. */ - flags &= ~LM_FLAG_TRY; loops++; /* Check that fs hasn't grown if writing to rindex */ if (ip == GFS2_I(sdp->sd_rindex) && !sdp->sd_rindex_uptodate) { |