diff options
Diffstat (limited to 'fs/xfs/xfs_log_priv.h')
| -rw-r--r-- | fs/xfs/xfs_log_priv.h | 75 |
1 files changed, 57 insertions, 18 deletions
diff --git a/fs/xfs/xfs_log_priv.h b/fs/xfs/xfs_log_priv.h index 2b0aec37e73e..ec22c7a3867f 100644 --- a/fs/xfs/xfs_log_priv.h +++ b/fs/xfs/xfs_log_priv.h @@ -51,13 +51,11 @@ enum xlog_iclog_state { }; /* - * Flags to log ticket + * Log ticket flags */ -#define XLOG_TIC_INITED 0x1 /* has been initialized */ -#define XLOG_TIC_PERM_RESERV 0x2 /* permanent reservation */ +#define XLOG_TIC_PERM_RESERV 0x1 /* permanent reservation */ #define XLOG_TIC_FLAGS \ - { XLOG_TIC_INITED, "XLOG_TIC_INITED" }, \ { XLOG_TIC_PERM_RESERV, "XLOG_TIC_PERM_RESERV" } /* @@ -242,6 +240,7 @@ struct xfs_cil_ctx { struct xfs_log_vec *lv_chain; /* logvecs being pushed */ struct list_head iclog_entry; struct list_head committing; /* ctx committing list */ + wait_queue_head_t push_wait; /* background push throttle */ struct work_struct discard_endio_work; }; @@ -318,13 +317,53 @@ struct xfs_cil { * tries to keep 25% of the log free, so we need to keep below that limit or we * risk running out of free log space to start any new transactions. * - * In order to keep background CIL push efficient, we will set a lower - * threshold at which background pushing is attempted without blocking current - * transaction commits. A separate, higher bound defines when CIL pushes are - * enforced to ensure we stay within our maximum checkpoint size bounds. - * threshold, yet give us plenty of space for aggregation on large logs. + * In order to keep background CIL push efficient, we only need to ensure the + * CIL is large enough to maintain sufficient in-memory relogging to avoid + * repeated physical writes of frequently modified metadata. If we allow the CIL + * to grow to a substantial fraction of the log, then we may be pinning hundreds + * of megabytes of metadata in memory until the CIL flushes. This can cause + * issues when we are running low on memory - pinned memory cannot be reclaimed, + * and the CIL consumes a lot of memory. Hence we need to set an upper physical + * size limit for the CIL that limits the maximum amount of memory pinned by the + * CIL but does not limit performance by reducing relogging efficiency + * significantly. + * + * As such, the CIL push threshold ends up being the smaller of two thresholds: + * - a threshold large enough that it allows CIL to be pushed and progress to be + * made without excessive blocking of incoming transaction commits. This is + * defined to be 12.5% of the log space - half the 25% push threshold of the + * AIL. + * - small enough that it doesn't pin excessive amounts of memory but maintains + * close to peak relogging efficiency. This is defined to be 16x the iclog + * buffer window (32MB) as measurements have shown this to be roughly the + * point of diminishing performance increases under highly concurrent + * modification workloads. + * + * To prevent the CIL from overflowing upper commit size bounds, we introduce a + * new threshold at which we block committing transactions until the background + * CIL commit commences and switches to a new context. While this is not a hard + * limit, it forces the process committing a transaction to the CIL to block and + * yeild the CPU, giving the CIL push work a chance to be scheduled and start + * work. This prevents a process running lots of transactions from overfilling + * the CIL because it is not yielding the CPU. We set the blocking limit at + * twice the background push space threshold so we keep in line with the AIL + * push thresholds. + * + * Note: this is not a -hard- limit as blocking is applied after the transaction + * is inserted into the CIL and the push has been triggered. It is largely a + * throttling mechanism that allows the CIL push to be scheduled and run. A hard + * limit will be difficult to implement without introducing global serialisation + * in the CIL commit fast path, and it's not at all clear that we actually need + * such hard limits given the ~7 years we've run without a hard limit before + * finding the first situation where a checkpoint size overflow actually + * occurred. Hence the simple throttle, and an ASSERT check to tell us that + * we've overrun the max size. */ -#define XLOG_CIL_SPACE_LIMIT(log) (log->l_logsize >> 3) +#define XLOG_CIL_SPACE_LIMIT(log) \ + min_t(int, (log)->l_logsize >> 3, BBTOB(XLOG_TOTAL_REC_SHIFT(log)) << 4) + +#define XLOG_CIL_BLOCKING_SPACE_LIMIT(log) \ + (XLOG_CIL_SPACE_LIMIT(log) * 2) /* * ticket grant locks, queues and accounting have their own cachlines @@ -439,14 +478,14 @@ xlog_write_adv_cnt(void **ptr, int *len, int *off, size_t bytes) void xlog_print_tic_res(struct xfs_mount *mp, struct xlog_ticket *ticket); void xlog_print_trans(struct xfs_trans *); -int -xlog_write( - struct xlog *log, - struct xfs_log_vec *log_vector, - struct xlog_ticket *tic, - xfs_lsn_t *start_lsn, - struct xlog_in_core **commit_iclog, - uint flags); +int xlog_write(struct xlog *log, struct xfs_log_vec *log_vector, + struct xlog_ticket *tic, xfs_lsn_t *start_lsn, + struct xlog_in_core **commit_iclog, uint flags, + bool need_start_rec); +int xlog_commit_record(struct xlog *log, struct xlog_ticket *ticket, + struct xlog_in_core **iclog, xfs_lsn_t *lsn); +void xfs_log_ticket_ungrant(struct xlog *log, struct xlog_ticket *ticket); +void xfs_log_ticket_regrant(struct xlog *log, struct xlog_ticket *ticket); /* * When we crack an atomic LSN, we sample it first so that the value will not |