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Merge branch 'for-linus' of git://oss.sgi.com/xfs/xfs

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* 'for-linus' of git://oss.sgi.com/xfs/xfs:
  xfs: force background CIL push under sustained load
This commit is contained in:
Linus Torvalds 2010-09-29 14:58:11 -07:00
commit 4193d91635
2 changed files with 30 additions and 19 deletions
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12
fs/xfs/xfs_log_cil.c
View File

@ -405,9 +405,15 @@ xlog_cil_push(
new_ctx = kmem_zalloc(sizeof(*new_ctx), KM_SLEEP|KM_NOFS);
new_ctx->ticket = xlog_cil_ticket_alloc(log);
/* lock out transaction commit, but don't block on background push */
/*
* Lock out transaction commit, but don't block for background pushes
* unless we are well over the CIL space limit. See the definition of
* XLOG_CIL_HARD_SPACE_LIMIT() for the full explanation of the logic
* used here.
*/
if (!down_write_trylock(&cil->xc_ctx_lock)) {
if (!push_seq)
if (!push_seq &&
cil->xc_ctx->space_used < XLOG_CIL_HARD_SPACE_LIMIT(log))
goto out_free_ticket;
down_write(&cil->xc_ctx_lock);
}
@ -422,7 +428,7 @@ xlog_cil_push(
goto out_skip;
/* check for a previously pushed seqeunce */
if (push_seq < cil->xc_ctx->sequence)
if (push_seq && push_seq < cil->xc_ctx->sequence)
goto out_skip;
/*

37
fs/xfs/xfs_log_priv.h
View File

@ -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.