diff options
Diffstat (limited to 'fs/xfs/xfs_log_priv.h')
| -rw-r--r-- | fs/xfs/xfs_log_priv.h | 37 |
1 files changed, 21 insertions, 16 deletions
diff --git a/fs/xfs/xfs_log_priv.h b/fs/xfs/xfs_log_priv.h index ced52b98b322..edcdfe01617f 100644 --- a/fs/xfs/xfs_log_priv.h +++ b/fs/xfs/xfs_log_priv.h @@ -426,13 +426,13 @@ struct xfs_cil { }; /* - * The amount of log space we should the CIL to aggregate is difficult to size. - * Whatever we chose we have to make we can get a reservation for the log space - * effectively, that it is large enough to capture sufficient relogging to - * reduce log buffer IO significantly, but it is not too large for the log or - * induces too much latency when writing out through the iclogs. We track both - * space consumed and the number of vectors in the checkpoint context, so we - * need to decide which to use for limiting. + * The amount of log space we allow the CIL to aggregate is difficult to size. + * Whatever we choose, we have to make sure we can get a reservation for the + * log space effectively, that it is large enough to capture sufficient + * relogging to reduce log buffer IO significantly, but it is not too large for + * the log or induces too much latency when writing out through the iclogs. We + * track both space consumed and the number of vectors in the checkpoint + * context, so we need to decide which to use for limiting. * * Every log buffer we write out during a push needs a header reserved, which * is at least one sector and more for v2 logs. Hence we need a reservation of @@ -459,16 +459,21 @@ struct xfs_cil { * checkpoint transaction ticket is specific to the checkpoint context, rather * than the CIL itself. * - * With dynamic reservations, we can basically make up arbitrary limits for the - * checkpoint size so long as they don't violate any other size rules. Hence - * the initial maximum size for the checkpoint transaction will be set to a - * quarter of the log or 8MB, which ever is smaller. 8MB is an arbitrary limit - * right now based on the latency of writing out a large amount of data through - * the circular iclog buffers. + * With dynamic reservations, we can effectively make up arbitrary limits for + * the checkpoint size so long as they don't violate any other size rules. + * Recovery imposes a rule that no transaction exceed half the log, so we are + * limited by that. Furthermore, the log transaction reservation subsystem + * 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. */ - -#define XLOG_CIL_SPACE_LIMIT(log) \ - (min((log->l_logsize >> 2), (8 * 1024 * 1024))) +#define XLOG_CIL_SPACE_LIMIT(log) (log->l_logsize >> 3) +#define XLOG_CIL_HARD_SPACE_LIMIT(log) (3 * (log->l_logsize >> 4)) /* * The reservation head lsn is not made up of a cycle number and block number. |
