Hi, This patch reworks the "congestion" algorithms for resource group glocks to take into account intra-node demands as well as inter- node demands.
Signed-off-by: Bob Peterson <[email protected]> --- diff --git a/fs/gfs2/rgrp.c b/fs/gfs2/rgrp.c index ad62bfb..903f58b 100644 --- a/fs/gfs2/rgrp.c +++ b/fs/gfs2/rgrp.c @@ -1807,6 +1807,21 @@ static void try_rgrp_unlink(struct gfs2_rgrpd *rgd, u64 *last_unlinked, u64 skip } /** + * 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 inline bool gfs2_rgrp_used_recently(const struct gfs2_rgrpd *rgd, + u64 msecs) +{ + return (ktime_before(ktime_get_real(), + ktime_add(rgd->rd_gl->gl_dstamp, + ms_to_ktime(msecs)))); +} + +/** * 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) @@ -1833,7 +1848,7 @@ static void try_rgrp_unlink(struct gfs2_rgrpd *rgd, u64 *last_unlinked, u64 skip * Returns: A boolean verdict on the congestion status */ -static bool gfs2_rgrp_congested(const struct gfs2_rgrpd *rgd, int loops) +static bool gfs2_rgrp_congested_dlm(const struct gfs2_rgrpd *rgd, int loops) { const struct gfs2_glock *gl = rgd->rd_gl; const struct gfs2_sbd *sdp = gl->gl_name.ln_sbd; @@ -1845,6 +1860,11 @@ static bool gfs2_rgrp_congested(const struct gfs2_rgrpd *rgd, int loops) u64 var; int cpu, nonzero = 0; + /* If it hasn't been used recently we can't judge the statistics, so + assume it's not congested. */ + if (!gfs2_rgrp_used_recently(rgd, HZ)) + return false; + preempt_disable(); for_each_present_cpu(cpu) { st = &per_cpu_ptr(sdp->sd_lkstats, cpu)->lkstats[LM_TYPE_RGRP]; @@ -1880,21 +1900,66 @@ static bool gfs2_rgrp_congested(const struct gfs2_rgrpd *rgd, int loops) } /** - * gfs2_rgrp_used_recently - * @rs: The block reservation with the rgrp to test - * @msecs: The time limit in milliseconds + * fast_to_acquire - determine if a resource group will be fast to acquire * - * Returns: True if the rgrp glock has been used within the time limit + * If this is one of our preferred rgrps, it should be quicker to acquire, + * because we tried to set ourselves up as dlm lock master. + */ +static inline bool fast_to_acquire(const struct gfs2_rgrpd *rgd) +{ + struct gfs2_glock *gl = rgd->rd_gl; + + if (gl->gl_state != LM_ST_UNLOCKED && list_empty(&gl->gl_holders) && + !test_bit(GLF_DEMOTE_IN_PROGRESS, &gl->gl_flags) && + !test_bit(GLF_DEMOTE, &gl->gl_flags)) + return true; + if (rgd->rd_flags & GFS2_RDF_PREFERRED) + return true; + return false; +} + +/** + * gfs2_rgrp_congested - decide whether a rgrp glock is congested + * @rgd: The rgrp in question + * @loops: An indication of how picky we can be (0=very, 1=less so) + * + * There are two kinds of congestion: inter-node and intra-node. + * + * Inter-node congestion is where multiple nodes all want to allocate blocks + * inside the same rgrp, which means they need to trade the rgrp glock back + * and forth, which is a slow process. To mitigate this, we use glock + * statistics to predict whether the glock is historically fast to acquire. + * + * Intra-node congestion is where you have multiple processes on the same + * node, all trying to allocate blocks in the same rgrp. There's nothing wrong + * with doing so, but each process needs to wait for the other to release the + * rgrp glock before it may proceed. We can predict whether a rgrp glock is + * congested by how many block reservations are currently attached. + * + * Both kinds of congestion can hurt performance, but it's faster to check + * intra-node, so we do that first. After all, why bother to check if we can + * get the glock quickly from DLM if other processes have also used that + * same reasoning. + * + * We know the number of loops we've been around, so we know how desperate we + * are to find something. On first loop, call it congested if anyone else has + * a block reservation. On second loop, call it congested if it's not fast to + * acquire. */ -static bool gfs2_rgrp_used_recently(const struct gfs2_blkreserv *rs, - u64 msecs) +static bool gfs2_rgrp_congested(const struct gfs2_rgrpd *rgd, int loops) { - u64 tdiff; + /* Check for intra-node congestion */ + if (loops == 0 && !RB_EMPTY_ROOT(&rgd->rd_rstree)) + return true; + + if (loops == 1 && !fast_to_acquire(rgd)) + return true; - tdiff = ktime_to_ns(ktime_sub(ktime_get_real(), - rs->rs_rbm.rgd->rd_gl->gl_dstamp)); + /* Check for inter-node congestion */ + if (rgd->rd_sbd->sd_lockstruct.ls_ops->lm_lock) /* lock_dlm */ + return gfs2_rgrp_congested_dlm(rgd, loops); - return tdiff > (msecs * 1000 * 1000); + return false; } static u32 gfs2_orlov_skip(const struct gfs2_inode *ip) @@ -1921,25 +1986,6 @@ static bool gfs2_select_rgrp(struct gfs2_rgrpd **pos, const struct gfs2_rgrpd *b } /** - * fast_to_acquire - determine if a resource group will be fast to acquire - * - * If this is one of our preferred rgrps, it should be quicker to acquire, - * because we tried to set ourselves up as dlm lock master. - */ -static inline int fast_to_acquire(struct gfs2_rgrpd *rgd) -{ - struct gfs2_glock *gl = rgd->rd_gl; - - if (gl->gl_state != LM_ST_UNLOCKED && list_empty(&gl->gl_holders) && - !test_bit(GLF_DEMOTE_IN_PROGRESS, &gl->gl_flags) && - !test_bit(GLF_DEMOTE, &gl->gl_flags)) - return 1; - if (rgd->rd_flags & GFS2_RDF_PREFERRED) - return 1; - return 0; -} - -/** * gfs2_inplace_reserve - Reserve space in the filesystem * @ip: the inode to reserve space for * @ap: the allocation parameters @@ -1995,7 +2041,6 @@ int gfs2_inplace_reserve(struct gfs2_inode *ip, struct gfs2_alloc_parms *ap) !fast_to_acquire(rs->rs_rbm.rgd)) goto next_rgrp; if ((loops < 2) && - gfs2_rgrp_used_recently(rs, 1000) && gfs2_rgrp_congested(rs->rs_rbm.rgd, loops)) goto next_rgrp; }
