[PATCH v3 2/2] xfs: make xfs_log_iovec independent from xfs_log_vec and free it early

alexjlzheng
2024-06-26T04:49:23Z

From: Jinliang Zheng <alexjlzheng@tencent.com>

When the contents of the xfs_log_vec/xfs_log_iovec combination are
written to iclog, xfs_log_iovec loses its meaning in continuing to exist
in memory, because iclog already has a copy of its contents. We only
need to keep xfs_log_vec that takes up very little memory to find the
xfs_log_item that needs to be added to AIL after we flush the iclog into
the disk log space.

Because xfs_log_iovec dominates most of the memory in the
xfs_log_vec/xfs_log_iovec combination, retaining xfs_log_iovec until
iclog is flushed into the disk log space and releasing together with
xfs_log_vec is a significant waste of memory.

This patch separates the memory of xfs_log_iovec from that of
xfs_log_vec, and releases the memory of xfs_log_iovec in advance to save
memory.

Signed-off-by: Jinliang Zheng <alexjlzheng@tencent.com>
---
fs/xfs/xfs_log.c | 2 ++
fs/xfs/xfs_log.h | 8 ++++++--
fs/xfs/xfs_log_cil.c | 34 ++++++++++++++++++++--------------
3 files changed, 28 insertions(+), 16 deletions(-)

diff --git a/fs/xfs/xfs_log.c b/fs/xfs/xfs_log.c
index 49e676061f2f..84a01ce61c96 100644
--- a/fs/xfs/xfs_log.c
+++ b/fs/xfs/xfs_log.c
@@ -2527,6 +2527,8 @@ xlog_write(
xlog_write_full(lv, ticket, iclog, &log_offset,
&len, &record_cnt, &data_cnt);
}
+ if (lv->lv_flags & XFS_LOG_VEC_DYNAMIC)
+ kvfree(lv->lv_iovecp);
}
ASSERT(len == 0);

diff --git a/fs/xfs/xfs_log.h b/fs/xfs/xfs_log.h
index 9cc10acf7bcd..7d0ae93e9e79 100644
--- a/fs/xfs/xfs_log.h
+++ b/fs/xfs/xfs_log.h
@@ -6,6 +6,8 @@
#ifndef __XFS_LOG_H__
#define __XFS_LOG_H__

+#define XFS_LOG_VEC_DYNAMIC (1 << 0)
+
struct xfs_cil_ctx;

struct xfs_log_vec {
@@ -17,7 +19,8 @@ struct xfs_log_vec {
char *lv_buf; /* formatted buffer */
int lv_bytes; /* accounted space in buffer */
int lv_buf_len; /* aligned size of buffer */
- int lv_size; /* size of allocated lv */
+ int lv_size; /* size of allocated iovecp + buf */
+ int lv_flags; /* lv flags */
};

extern struct kmem_cache *xfs_log_vec_cache;
@@ -71,7 +74,8 @@ xlog_finish_iovec(struct xfs_log_vec *lv, struct xfs_log_iovec *vec,
vec->i_len = len;

/* Catch buffer overruns */
- ASSERT((void *)lv->lv_buf + lv->lv_bytes <= (void *)lv + lv->lv_size);
+ ASSERT((void *)lv->lv_buf + lv->lv_bytes <=
+ (void *)lv->lv_iovecp + lv->lv_size);
}

/*
diff --git a/fs/xfs/xfs_log_cil.c b/fs/xfs/xfs_log_cil.c
index f51cbc6405c1..0175bd68590a 100644
--- a/fs/xfs/xfs_log_cil.c
+++ b/fs/xfs/xfs_log_cil.c
@@ -219,8 +219,7 @@ static inline int
xlog_cil_iovec_space(
uint niovecs)
{
- return round_up((sizeof(struct xfs_log_vec) +
- niovecs * sizeof(struct xfs_log_iovec)),
+ return round_up(niovecs * sizeof(struct xfs_log_iovec),
sizeof(uint64_t));
}

@@ -279,6 +278,7 @@ xlog_cil_alloc_shadow_bufs(

list_for_each_entry(lip, &tp->t_items, li_trans) {
struct xfs_log_vec *lv;
+ struct xfs_log_iovec *lvec;
int niovecs = 0;
int nbytes = 0;
int buf_size;
@@ -330,8 +330,8 @@ xlog_cil_alloc_shadow_bufs(
* if we have no shadow buffer, or it is too small, we need to
* reallocate it.
*/
- if (!lip->li_lv_shadow ||
- buf_size > lip->li_lv_shadow->lv_size) {
+ lv = lip->li_lv_shadow;
+ if (!lv || buf_size > lv->lv_size) {
/*
* We free and allocate here as a realloc would copy
* unnecessary data. We don't use kvzalloc() for the
@@ -339,22 +339,27 @@ xlog_cil_alloc_shadow_bufs(
* the buffer, only the log vector header and the iovec
* storage.
*/
- kvfree(lip->li_lv_shadow);
- lv = xlog_kvmalloc(buf_size);
+ if (lv)
+ kvfree(lv->lv_iovecp);
+ else
+ lv = kmem_cache_alloc(xfs_log_vec_cache,
+ GFP_KERNEL | __GFP_NOFAIL);

- memset(lv, 0, xlog_cil_iovec_space(niovecs));
+ memset(lv, 0, sizeof(struct xfs_log_vec));
+ lvec = xlog_kvmalloc(buf_size);
+ memset(lvec, 0, xlog_cil_iovec_space(niovecs));

+ lv->lv_flags |= XFS_LOG_VEC_DYNAMIC;
INIT_LIST_HEAD(&lv->lv_list);
lv->lv_item = lip;
lv->lv_size = buf_size;
if (ordered)
lv->lv_buf_len = XFS_LOG_VEC_ORDERED;
else
- lv->lv_iovecp = (struct xfs_log_iovec *)&lv[1];
+ lv->lv_iovecp = lvec;
lip->li_lv_shadow = lv;
} else {
/* same or smaller, optimise common overwrite case */
- lv = lip->li_lv_shadow;
if (ordered)
lv->lv_buf_len = XFS_LOG_VEC_ORDERED;
else
@@ -366,9 +371,9 @@ xlog_cil_alloc_shadow_bufs(
lv->lv_niovecs = niovecs;

/* The allocated data region lies beyond the iovec region */
- lv->lv_buf = (char *)lv + xlog_cil_iovec_space(niovecs);
+ lv->lv_buf = (char *)lv->lv_iovecp +
+ xlog_cil_iovec_space(niovecs);
}
-
}

/*
@@ -502,7 +507,7 @@ xlog_cil_insert_format_items(
/* reset the lv buffer information for new formatting */
lv->lv_buf_len = 0;
lv->lv_bytes = 0;
- lv->lv_buf = (char *)lv +
+ lv->lv_buf = (char *)lv->lv_iovecp +
xlog_cil_iovec_space(lv->lv_niovecs);
} else {
/* switch to shadow buffer! */
@@ -703,7 +708,7 @@ xlog_cil_free_logvec(
while (!list_empty(lv_chain)) {
lv = list_first_entry(lv_chain, struct xfs_log_vec, lv_list);
list_del_init(&lv->lv_list);
- kvfree(lv);
+ kmem_cache_free(xfs_log_vec_cache, lv);
}
}

@@ -1544,7 +1549,8 @@ xlog_cil_process_intents(
set_bit(XFS_LI_WHITEOUT, &ilip->li_flags);
trace_xfs_cil_whiteout_mark(ilip);
len += ilip->li_lv->lv_bytes;
- kvfree(ilip->li_lv);
+ kvfree(ilip->li_lv->lv_iovecp);
+ kmem_cache_free(xfs_log_vec_cache, ilip->li_lv);
ilip->li_lv = NULL;

xfs_trans_del_item(lip);
--
2.41.1